Majibu na maswali ya tathmini ya ustadi wa LinkedIn - Java

Java is one of the most popular and widely used programming languages in the world. Pia ni ujuzi ambao waajiri wengi hutafuta wakati wa kuajiri watengenezaji programu. If you want to showcase your Java proficiency and stand out from the crowd, you might want to take the Tathmini ya ujuzi wa LinkedIn Tofauti kuu kati ya Java. This is a short online test that measures your knowledge of Java fundamentals, sintaksia, and best practices. But how can you prepare for this test and ace it? That’s where this blog post comes in handy.

Nahitaji Maarifa Katika RNA Vs DNA, you will find some of the most common questions and answers that appear on the Tathmini ya ujuzi wa LinkedIn for Java. You can use these as a reference to review the concepts and topics that are likely to be tested. You can also test yourself by trying to answer the questions before looking at the solutions. Kwa kufanya hivi, you will boost your confidence and readiness for the real test. Kwa hivyo, bila ado zaidi, let’s dive into the maswali na majibu.

Q1. Given the string “jordgubbar” saved in a variable called fruit, what would `fruit.substring(2, 5)` kurudi?

rawb
raw
awb
traw

Reasoning: The substring method accepts two arguments.

The first argument is the index to start(includes that char at 2)
and the second the index of the string to end the substring(excludes the char at 5).
Strings in Java are like arrays of chars.
Kwa hiyo, the method will return “raw” as those are the chars in indexes 2,3 na 4.
You can also take the ending index and subtract the beginning index from it, to determine how many chars will be included in the substring (5-2=3).

Q2. How can you achieve runtime polymorphism in Java?

method overloading
method overrunning
method overriding
method calling

Q3. Given the following definitions, which of these expressions will Mdomo unaganda kama matope yaliyochomwa jangwani evaluate to true?

boolean b1 = true, b2 = false; int i1 = 1, i2 = 2;

(i1 | i2) == 3
i2 && b1
b1 || !b2
(i1 ^ i2) < 4

Reasoning: i2 && b1 are not allowed between int and boolean.

Q4. What is the output of this code?

class Main {
  public static void main (String[] args) {
    int array[] = {1, 2, 3, 4};
    for (int i = 0; i < array.size(); i++) {
       System.out.print(array[i]);
    }
  }
}

It will not compile because of line 4.
It will not compile because of line 3.
123
1234

Reasoning: array.size() is invalid, to get the size or length of the array array.length can be used.

Q5. Which of the following can replace the CODE SNIPPET to make the code below print “Hello World”?

interface Interface1 {
    static void print() {
        System.out.print("Hello");
    }
}

interface Interface2 {
    static void print() {
        System.out.print("World!");
    }
}

super1.print(); super2.print();
this.print();
super.print();
Interface1.print(); Interface2.print();

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Q6. What does the following code print?

String str = "abcde";
str.trim();
str.toUpperCase();
str.substring(3, 4);
System.out.println(str);

CD
CDE
D
“abcde”

Reasoning: You should assign the result of trim back to the String variable. Byerley anakumbuka, it is not going to work, because strings in Java are immutable.

Swali 7. What is the result of this code?

class Main {
    public static void main (String[] args){
        System.out.println(print(1));
    }
    static Exception print(int i){
        if (i>0) {
            return new Exception();
        } else {
            throw new RuntimeException();
        }
    }
}

It will show a stack trace with a runtime exception.
“java.lang.Exception”
It will run and throw an exception.
It will not compile.

Q8. Which class can compile given these declarations?

interface One {
    default void method() {
        System.out.println("One");
    }
}

interface Two {
    default void method () {
        System.out.println("One");
    }
}

class Three implements One, Two {
    public void method() {
        super.One.method();
    }
}

class Three implements One, Two {
    public void method() {
        One.method();
    }
}

class Three implements One, Two {
}

class Three implements One, Two {
    public void method() {
        One.super.method();
    }
}

Q9. What is the output of this code?

class Main {
    public static void main (String[] args) {
        List list = new ArrayList();
        list.add("hello");
        list.add(2);
        System.out.print(list.get(0) instanceof Object);
        System.out.print(list.get(1) instanceof Integer);
    }
}

The code does not compile.
truefalse
truetrue
falsetrue

Q10. Given the following two classes, what will be the output of the Main class?

package mypackage;
public class Math {
    public static int abs(int num){
        return num < 0 ? -num : num;
    }
}
package mypackage.elementary;
public class Math {
    public static int abs (int num) {
        return -num;
    }
}

import mypackage.Math;
import mypackage.elementary.*;

class Main {
    public static void main (String args[]){
        System.out.println(Math.abs(123));
    }
}

Lines 1 na 2 generate compiler errors due to class name conflicts.
“-123”
It will throw an exception on line 5.
“123”

Maelezo: Jibu ni “123”. The abs() method evaluates to the one inside mypackage.Math class, because the import statements of the form:

import packageName.subPackage.*

ni Type-Import-on-Demand Declarations, ambayo never causes any other declaration to be shadowed.

Q11. What is the result of this code?

class MainClass {
    final String message() {
        return "Hello!";
    }
}

class Main extends MainClass {
    public static void main(String[] args) {
        System.out.println(message());
    }

     String message() {
         return "World!";
     }
 }

It will not compile because of line 10.
“Habari!”
It will not compile because of line 2.
“World!”

Maelezo: Compilation error at line 10 because of final methods cannot be overridden, and here message() is a final method, and also note that Non-static method message() cannot be referenced from a static context.

Q12. Given this code, which command will output “2”?

class Main {
    public static void main(String[] args) {
        System.out.println(args[2]);
    }
}

java Main 1 2 "3 4" 5
java Main 1 "2" "2" 5
java Main.class 1 "2" 2 5
java Main 1 "2" "3 4" 5

Q13. What is the output of this code?

class Main {
    public static void main(String[] args){
        int a = 123451234512345;
        System.out.println(a);
    }
}

“123451234512345”
Hakuna kitu – this will not compile.
a negative integer value
“12345100000”

Reasoning: The int type in Java can be used to represent any whole number from -2147483648 kwa 2147483647. Kwa hiyo, this code will not compile as the number assigned to ‘a’ is larger than the int type can hold.

Q14. What is the output of this code?

class Main {
    public static void main (String[] args) {
        String message = "Hello world!";
        String newMessage = message.substring(6, 12)
            + message.substring(12, 6);
        System.out.println(newMessage);
    }
}

The code does not compile.
A runtime exception is thrown.
“dunia!!dunia”
“dunia!dunia!”

Q15. How do you write a for-each loop that will iterate over ArrayList<Pencil>pencilCase?

for (Pencil pencil : pencilCase) {}
for (pencilCase.next()) {}
for (Pencil pencil : pencilCase.iterator()) {}
for (pencil in pencilCase) {}

Q16. What does this code print?

System.out.print("apple".compareTo("banana"));

0
positive number
negative number
compilation error

Q17. You have an ArrayList of names that you want to sort alphabetically. Which approach would Mdomo unaganda kama matope yaliyochomwa jangwani kazi?

names.sort(Comparator.comparing(String::toString))
Collections.sort(names)
names.sort(List.DESCENDING)
names.stream().sorted((s1, s2) -> s1.compareTo(s2)).collect(Collectors.toList())

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Q18. By implementing encapsulation, you cannot directly access the class’s _ properties unless you are writing code inside the class itself.

Privat
mlinzi wa kuongezeka
no-modifier
umma

Q19. Which is the most up-to-date way to instantiate the current date?

new SimpleDateFormat("yyyy-MM-dd").format(new Date())
new Date(System.currentTimeMillis())
LocalDate.now()
Calendar.getInstance().getTime()

Maelezo: LocalDate is the newest class added in Java 8

Q20. Fill in the blank to create a piece of code that will tell whether `int0` is divisible by `5`:

boolean isDivisibleBy5 = _____

int0 / 5 ? true: false
int0 % 5 == 0
int0 % 5 != 5
Math.isDivisible(int0, 5)

Q21. How many times will this code print “Hello World!”?

class Main {
    public static void main(String[] args){
        for (int i=0; i<10; i=i++){
            i+=1;
            System.out.println("Hello World!");
        }
    }
}

10 nyakati
9 nyakati
5 nyakati
infinite number of times

Maelezo: Observe the loop increment. It’s not an increment, it’s an assignment(chapisho).

Q22. The runtime system starts your program by calling which function first?

chapa
ya kurudia
hello
main

Q23. What code would you use in Constructor A to call Constructor B?

public class Jedi {
  /* Constructor A */
  Jedi(String name, String species){}

  /* Constructor B */
  Jedi(String name, String species, boolean followsTheDarkSide){}
}

Jedi(jina, aina, tofauti kati ya makosa na uongo)
new Jedi(jina, aina, tofauti kati ya makosa na uongo)
kama tasnifu ya kitaaluma(jina, aina, tofauti kati ya makosa na uongo)
mkuu(jina, aina, tofauti kati ya makosa na uongo)

Kumbuka: This code won’t compile, possibly a broken code sample.

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Q24. “An anonymous class requires a zero-argument constructor.” that’s not true?

An anonymous class may specify an abstract base class as its base type.
An anonymous class does not require a zero-argument constructor.
An anonymous class may specify an interface as its base type.
An anonymous class may specify both an abstract class and interface as base types.

Q25. What will this program print out to the console when executed?

import java.util.LinkedList;

public class Main {
    public static void main(String[] args){
        LinkedList<Integer> list = new LinkedList<>();
        list.add(5);
        list.add(1);
        list.add(10);
        System.out.println(list);
    }
}

[5, 1, 10]
[10, 5, 1]
[1, 5, 10]
[10, 1, 5]

Q26. What is the output of this code?

class Main {
    public static void main(String[] args){
       String message = "Hello";
       for (int i = 0; i<message.length(); i++){
          System.out.print(message.charAt(i+1));
       }
    }
}

“Habari”
A runtime exception is thrown.
The code does not compile.
“ello”

Q27. Object-oriented programming is a style of programming where you organize your program around _ and data, rather than _ and logic.

kazi; actions
vitu; actions
actions; kazi
actions; vitu

Q28. What statement returns true if “nifty” is of type String?

"nifty".getType().equals("String")
"nifty".getType() == String
"nifty".getClass().getSimpleName() == "String"
"nifty" instanceof String

Q29. What is the output of this code?

import java.util.*;
class Main {
    public static void main(String[] args) {
        List<Boolean> list = new ArrayList<>();
        list.add(true);
        list.add(Boolean.parseBoolean("FalSe"));
        list.add(Boolean.TRUE);
        System.out.print(list.size());
        System.out.print(list.get(1) instanceof Boolean);
    }
}

A runtime exception is thrown.
3tofauti kati ya makosa na uongo
2kweli
3kweli

Q30. What is the result of this code?

class Main {
    Object message() {
        return "Hello!";
    }
    public static void main(String[] args) {
        System.out.print(new Main().message());
        System.out.print(new Main2().message());
    }
}
class Main2 extends Main {
    String message() {
        return "World!";
    }
}

It will not compile because of line 7.
Habari!Habari!
Habari!World!
It will not compile because of line 11.

Q31. What method can be used to create a new instance of an object?

another instance
shamba
constructor
private method

Q32. Which is the most reliable expression for testing whether the values of two string variables are the same?

string1 == string2
string1 = string2
string1.matches(string2)
string1.equals(string2)

Q33. Which letters will print when this code is run?

public static void main(String[] args) {
    try {
        System.out.println("A");
        badMethod();
        System.out.println("B");
    } catch (Exception ex) {
        System.out.println("C");
    } finally {
        System.out.println("D");
    }
}
public static void badMethod() {
    throw new Error();
}

A, B, na D
A, C, na D
C and D
A and D

Maelezo: Error is not inherited from Exception.

Q34. What is the output of this code?

class Main {
    static int count = 0;
    public static void main(String[] args) {
        if (count < 3) {
            count++;
            main(null);
        } else {
            return;
        }
        System.out.println("Hello World!");
    }
}

It will throw a runtime exception.
It will not compile.
It will print “Hello World!” three times.
It will run forever.

Q35. What is the output of this code?

import java.util.*;
class Main {
    public static void main(String[] args) {
        String[] array = {"abc", "2", "10", "0"};
        List<String> list = Arrays.asList(array);
        Collections.sort(list);
        System.out.println(Arrays.toString(array));
    }
}

[abc, 0, 2, 10]
The code does not compile.
[abc, 2, 10, 0]
[0, 10, 2, abc]

Maelezo: The java.util.Arrays.asList(T... a) returns a fixed-size list backed by the specified array. (Changes to the returned list “write through” to the array.)

Q36. What is the output of this code?

class Main {
    public static void main(String[] args) {
        String message = "Hello";
        print(message);
        message += "World!";
        print(message);
    }
    static void print(String message) {
        System.out.print(message);
        message += " ";
    }
}

Hello World!
HelloHelloWorld!
Hello Hello World!
Hello HelloWorld!

Q37. What is displayed when this code is compiled and executed?

public class Main {
    public static void main(String[] args) {
        int x = 5;
        x = 10;
        System.out.println(x);
    }
}

x
null
10
5

Q38. Which approach cannot be used to iterate over a List named theList?

for (int i = 0; i < theList.size(); i++) {
    System.out.println(theList.get(i));
}

for (Object object : theList) {
    System.out.println(object);
}

Iterator it = theList.iterator();
for (it.hasNext()) {
    System.out.println(it.next());
}

theList.forEach(System.out::println);

Maelezo: for (it.hasNext()) should be while (it.hasNext()).

Q39. What method signature will work with this code?

boolean healthyOrNot = isHealthy("avocado");

public void isHealthy(String avocado)
boolean isHealthy(String string)
public isHealthy(“avocado”)
private String isHealthy(String food)

Q40. Which are valid keywords in a Java module descriptor (module-info.java)?

hutoa, employs
uagizaji, exports
consumes, supplies
requires, exports

Q41. Which type of variable keeps a constant value once it is assigned?

non-static
static
mwisho
Privat

Q42. How does the keyword `volatile` affect how a variable is handled?

It will be read by only one thread at a time.
It will be stored on the hard drive.
It will never be cached by the CPU.
It will be preferentially garbage collected.

Q43. What is the result of this code?

char smooch = 'x';
System.out.println((int) smooch);

an alphanumeric character
a negative number
a positive number
a ClassCastException

Q44. You get a NullPointerException. What is the most likely cause?

A file that needs to be opened cannot be found.
A network connection has been lost in the middle of communications.
Your code has used up all available memory.
The object you are using has not been instantiated.

Q45. How would you fix this code so that it compiles?

public class Nosey {
    int age;
    public static void main(String[] args) {
        System.out.println("Your age is: " + age);
    }
}

Make age static.
Make age global.
Make age public.
Initialize age to a number.

Q46. Add a Duck called “Waddles” to the ArrayList ducks.

public class Duck {
    private String name;
    Duck(String name) {}
}

Duck waddles = new Duck(); ducks.add(waddles);
Duck duck = new Duck("Waddles"); ducks.add(waddles);
ducks.add(new Duck("Waddles"));
ducks.add(new Waddles());

Q47. If you encounter `UnsupportedClassVersionError` it means the code was `_` on a newer version of Java than the JRE `_` hiyo.

executed; interpreting
executed; compiling
compiled; kutekeleza
compiled, translating

Q48. Given this class, how would you make the code compile?

public class TheClass {
    private final int x;
}

public TheClass() {
    x += 77;
}

public TheClass() {
    x = null;
}

public TheClass() {
    x = 77;
}

private void setX(int x) {
    this.x = x;
}
public TheClass() {
    setX(77);
}

Maelezo: final class members are allowed to be assigned only in three places: declaration, constructor, or an instance-initializer block.

Q49. How many times f will be printed?

public class Solution {
    public static void main(String[] args) {
        for (int i = 44; i > 40; i--) {
            System.out.println("f");
        }
    }
}

4
3
5
A Runtime exception will be thrown

Q50. Which statements about `abstract` classes are true?

1. They can be instantiated.
2. They allow member variables and methods to be inherited by subclasses.
3. They can contain constructors.

1, 2, na 3
pekee 3
2 na 3
pekee 2

Q51. Which keyword lets you call the constructor of a parent class?

mzazi
mkuu
kama tasnifu ya kitaaluma
kutengwa kulipuuzwa kwa kiasi kikubwa katika miongo iliyopita ya karne ya ishirini

Q52. What is the result of this code?

  1: int a = 1;
  2: int b = 0;
  3: int c = a/b;
  4: System.out.println(c);

It will throw an ArithmeticException.
It will run and output 0.
It will not compile because of line 3.
It will run and output infinity.

Q53. Kwa kawaida, to access a static member of a class such as Math.PI, you would need to specify the class “Hisabati”. What would be the best way to allow you to use simply “PI” in your code?

Add a static import.
Declare local copies of the constant in your code.
This cannot be done. You must always qualify references to static members with the class from which they came from.
Put the static members in an interface and inherit from that interface.

Q54. Which keyword lets you use an interface?

extends
zana
inherits
Ingiza

Q55. Why are ArrayLists better than arrays?

You don’t have to decide the size of an ArrayList when you first make it.
You can put more items into an ArrayList than into an array.
ArrayLists can hold more kinds of objects than arrays.
You don’t have to decide the type of an ArrayList when you first make it.

Q56. Declare a variable that holds the first four digits of Π

int pi = 3.141;
decimal pi = 3.141;
double pi = 3.141;
float pi = 3.141;

Reasoning:

public class TestReal {
    public static void main (String[] argv)
    {
      double pi = 3.14159265;       //accuracy up to 15 digits
      float pi2 = 3.141F;           //accuracy up to 6-7 digits

      System.out.println ("Pi=" + pi);
      System.out.println ("Pi2=" + pi2);
    }
  }

The default Java type which Java will be used for a float variable will be double.
So, even if you declare any variable as float, what the compiler has to do is assign a double value to a float variable,
which is not possible. So, to tell the compiler to treat this value as a float, that 'F' is used.

Q57. Use the magic power to cast a spell

public class MagicPower {
    void castSpell(String spell) {}
}

new MagicPower().castSpell("expecto patronum");
MagicPower magicPower = new MagicPower(); magicPower.castSpell();
MagicPower.castSpell("expelliarmus");
new MagicPower.castSpell();

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Q58. What language construct serves as a blueprint containing an object’s properties and functionality?

constructor
instance
darasa
njia

Q59. What does this code print?

public static void main(String[] args) {
    int x=5,y=10;
    swapsies(x,y);
    System.out.println(x+" "+y);
}

static void swapsies(int a, int b) {
    int temp=a;
    a=b;
    b=temp;
}

10 10
5 10
10 5
5 5

Q60. What is the result of this code?

try {
    System.out.println("Hello World");
} catch (Exception e) {
    System.out.println("e");
} catch (ArithmeticException e) {
    System.out.println("e");
} finally {
    System.out.println("!");
}

Hello World
It will not compile because the second catch statement is unreachable
Hello World!
It will throw a runtime exception

Q61. Which is not a Java keyword

lakini juu ya extraversion
asili
kiolesura
unsigned

Maelezo: native is a part of the JNI interface.

Q62. Which operator would you use to find the remainder after division?

%
//
/
DIV

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Q63. Which choice is a disadvantage of inheritance?

Overridden methods of the parent class cannot be reused.
Responsibilities are not evenly distributed between parent and child classes.
Classes related by inheritance are tightly coupled to each other.
The internal state of the parent class is accessible to its children.

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Q64. How would you declare and initialize an array of 10 ints?

Array<Integer> numbers = new Array<Integer>(10);
Array[int] numbers = new Array[int](10);
int[] numbers = new int[10];
int numbers[] = int[10];

Q65. Refactor this event handler to a lambda expression:

groucyButton.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("Press me one more time..");
    }
});

groucyButton.addActionListener(ActionListener listener -> System.out.println("Press me one more time..."));
groucyButton.addActionListener((event) -> System.out.println("Press me one more time..."));
groucyButton.addActionListener(new ActionListener(ActionEvent e) {() -> System.out.println("Press me one more time...");});
groucyButton.addActionListener(() -> System.out.println("Press me one more time..."));

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Q66. Which functional interfaces does Java provide to serve as data types for lambda expressions?

Mtazamaji, Observable
Collector, Builder
Chuja, Ramani, Reduce
Consumer, Predicate, Supplier

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Q67. What is a valid use of the hashCode() njia?

encrypting user passwords
deciding if two instances of a class are equal
enabling HashMap to find matches faster
moving objects from a List to a HashMap

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Q68. What kind of relationship does “extends” denote?

uses-a
is-a
has-a
was-a

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Q69. How do you force an object to be garbage collected?

Set object to null and call Runtime.gc()
Set object to null and call System.gc()
Set object to null and call Runtime.getRuntime().runFinalization()
There is no way to force an object to be garbage-collected

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Q70. Java programmers commonly use design patterns. Some examples are the _, which helps create instances of a class, ya _, which ensures that only one instance of a class can be created; na _, which allows for a group of algorithms to be interchangeable.

static factory method; singleton; strategy pattern
strategy pattern; static factory method; singleton
creation pattern; singleton; prototype pattern
singleton; strategy pattern; static factory method

Q71. Using Java’s Reflection API, you can use _ to get the name of a class and _ to retrieve an array of its methods.

this.getClass().getSimpleName(); this.getClass().getDeclaredMethods()
this.getName(); this.getMethods()
Reflection.getName(kama tasnifu ya kitaaluma); Reflection.getMethods(kama tasnifu ya kitaaluma)
Reflection.getClass(kama tasnifu ya kitaaluma).getName(); Reflection.getClass(kama tasnifu ya kitaaluma).getMethods()

Q72. Which is not a valid lambda expression?

a -> false;
(a) -> false;
String a -> false;
(String a) -> false;

Q73. Which access modifier makes variables and methods visible only in the class where they are declared?

umma
mlinzi wa kuongezeka
nonmodifier
Privat

Q74. What type of variable can be assigned only once?

Privat
non-static
mwisho
static

Q75. How would you convert a String to an Int?

"21".intValue()
String.toInt("21")
Integer.parseInt("21")
String.valueOf("21")

Q76. What method should be added to the Duck class to print the name Moby?

public class Duck {
    private String name;

    Duck(String name) {
        this.name = name;
    }

    public static void main(String[] args) {
        System.out.println(new Duck("Moby"));
    }
}

public String toString() { return name; }
public void println() { System.out.println(name); }
String toString() { return this.name; }
public void toString() { System.out.println(this.name); }

Q77. Which operator is used to concatenate Strings in Java

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q78. How many times does this loop print “exterminate”?

for (int i = 44; i > 40; i--) {
    System.out.println("exterminate");
}

Ikiwa umewahi kutaka kuwa na mwingiliano mzuri na kupata watu upande wako
nne
tatu
five

Q79. What is the value of myCharacter after line 3 is run?

public class Main {
  public static void main (String[] args) {
    char myCharacter = "piper".charAt(3);
  }
}

lakini inaweza kuwa na faida ya kutosha kwamba helical itashinda juu ya fimbo ya muda mrefu
lakini haifanyi yaliyomo katika hisabati kuwa tofauti
e
i

Q80. When should you use a static method?

when your method is related to the object’s characteristics
when you want your method to be available independently of class instances
when your method uses an object’s instance variable
when your method is dependent on the specific instance that calls it

Q81. What phrase indicates that a function receives a copy of each argument passed to it rather than a reference to the objects themselves?

pass by reference
pass by occurrence
pass by value
API call

Q82. In Java, what is the scope of a method’s argument or parameter?

inside the method
both inside and outside the method
neither inside nor outside the method
outside the method

Q83. What is the output of this code?

public class Main {
  public static void main (String[] args) {
    int[] sampleNumbers = {8, 5, 3, 1};
    System.out.println(sampleNumbers[2]);
  }
}

Q84. Which change will make this code compile successfully?

public class Main {
  String MESSAGE ="Hello!";
  static void print(){
    System.out.println(message);
  }
  void print2(){}
}

Change line 2 kwa public static final String message
Change line 6 kwa public void print2(){}
Remove the body of the print2 method and add a semicolon.
Remove the body of the print njia.

Maelezo: Changing line 2 kwa public static final String message raises the error message not initialized in the default constructor.

Q85. What is the output of this code?

import java.util.*;
class Main {
  public static void main(String[] args) {
    String[] array = new String[]{"A", "B", "C"};
    List<String> list1 = Arrays.asList(array);
    List<String> list2 = new ArrayList<>(Arrays.asList(array));
    List<String> list3 = new ArrayList<>(Arrays.asList("A", new String("B"), "C"));
    System.out.print(list1.equals(list2));
    System.out.print(list1.equals(list3));
  }
}

falsefalse
truetrue
falsetrue
truefalse

Q86. Which code snippet is valid?

ArrayList<String> words = new ArrayList<String>(){"Hello", "World"};
ArrayList words = Arrays.asList("Hello", "World");
ArrayList<String> words = {"Hello", "World"};
ArrayList<String> words = new ArrayList<>(Arrays.asList("Hello", "World"));

Q87. What is the output of this code?

class Main {
  public static void main(String[] args) {
    StringBuilder sb = new StringBuilder("hello");
    sb.deleteCharAt(0).insert(0, "H").append(" World!");
    System.out.println(sb);
  }
}

It will not compile.
“Hello World!”
“hello”
???? The code effectively converts the initial “hello” ndani “HelloWorld!” by deleting the first character, inserting “H” mwanzoni, and appending ” World!” to the end.

Q88. How would you use the TaxCalculator to determine the amount of tax on $50?

class TaxCalculator {
  static calculate(total) {
    return total * .05;
  }
}

TaxCalculator.calculate(50);
new TaxCalculator.calculate(50);
hesabu(50);
new TaxCalculator.calculate($50);

Kumbuka: This code won’t compile, broken code sample.

Q89. Which characteristic does not apply to instances of java.util.HashSet?

uses hashcode of objects when inserted
contains unordred elements
contains unique elements
contains sorted elements

Maelezo: HashSet makes no guarantees as to the iteration order of the set; hasa, it does not guarantee that the order will remain constant over time.

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q90. What is the output?

import java.util.*;

public class Main {
    public static void main(String[] args)
    {
        PriorityQueue<Integer> queue = new PriorityQueue<>();
        queue.add(4);
        queue.add(3);
        queue.add(2);
        queue.add(1);

        while (queue.isEmpty() == false) {
            System.out.printf("%d", queue.remove());
        }
    }
}

1 3 2 4
4 2 3 1
1 2 3 4
4 3 2 1

Q91. What will this code print, assuming it is inside the main method of a class?

System.out.println("hello my friends".split(" ")[0]);

my
hellomyfriends
hello
Kunywa pombe kudhuru pia kunaweza kusababisha madhara kwa wengine

Q92. You have an instance of type Map<String, Integer> named instruments containing the following key-value pairs: guitar=1200, cello=3000, and drum=2000. If you add the new key-value pair cello=4500 to the Map using the put method, how many elements do you have in the Map when you call instruments.size()?

2
When calling the put method, Java will throw an exception
4
3

Q93. Which class acts as the root class for the Java Exception hierarchy?

Clonable
Throwable
Object
Inaweza kutambulika

Q94. Which class does not implement the java.util.Collection interface?

java.util.Vector
java.util.ArrayList
java.util.HashSet
java.util.HashMap

Maelezo: HashMap class implements Map interface.

Q95. You have a variable of named `employees` of type `List<Employee>` containing multiple entries. The `Employee` type has a method `getName()` that returns the employee name. Which statement properly extracts a list of employee names?

employees.collect(employee -> employee.getName());
employees.filter(Employee::getName).collect(Collectors.toUnmodifiableList());
employees.stream().map(Employee::getName).collect(Collectors.toList());
employees.stream().collect((e) -> e.getName());

Q96. This code does not compile. What needs to be changed so that it does?

public enum Direction {
    EAST("E"),
    WEST("W"),
    NORTH("N"),
    SOUTH("S");

    private final String shortCode;

    public String getShortCode() {
        return shortCode;
    }
}

Add a constructor that accepts a String parameter and assigns it to the field shortCode.
Remove the final keyword for the field shortCode.
All enums need to be defined on a single line of code.
Add a setter method for the field shortCode.

Q97. Which language feature ensures that objects implementing the `AutoCloseable` interface are closed when it completes?

try-catch-finally
try-finally-close
try-with-resources
try-catch-close

Q98. What code should go in line 3?

class Main {
    public static void main(String[] args) {
        array[0] = new int[]{1, 2, 3};
        array[1] = new int[]{4, 5, 6};
        array[2] = new int[]{7, 8, 9};
        for (int i = 0; i < 3; i++)
            System.out.print(array[i][1]); //prints 258
    }
 }

int[][] array = new int[][];
int[][] array = new int[3][3];
int[][] array = new int[2][2];
int[][] array = [][];

Q99. Is this an example of method overloading or overriding?

class Car {
    public void accelerate() {}
}
class Lambo extends Car {
    public void accelerate(int speedLimit) {}
    public void accelerate() {}
}

neither
zote mbili
overloading
overriding

Q100. Which choice is the best data type for working with money in Java?

kuelea
String
mara mbili
BigDecimal

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q101. Which statement about constructors is not true?

A class can have multiple constructors with a different parameter list.
You can call another constructor with this au super.
A constructor does not define a return value.
Every class must explicitly define a constructor without parameters.

Q102. What language feature allows types to be parameters on classes, violesura, and methods in order to reuse the same code for different data types?

Regular Expressions
Tafakari
Generics
Concurrency

Q103. What will be printed?

public class Berries{

    String berry = "blue";

    public static void main(String[] args) {
        new Berries().juicy("straw");
    }
    void juicy(String berry){
        this.berry = "rasp";
        System.out.println(berry + "berry");
    }
}

rasiberi
strawberry
blueberry
rasp

Q104. What is the value of `forestCount` after this code executes?

Map<String, Integer> forestSpecies = new HashMap<>();

forestSpecies.put("Amazon", 30000);
forestSpecies.put("Congo", 10000);
forestSpecies.put("Daintree", 15000);
forestSpecies.put("Amazon", 40000);

int forestCount = forestSpecies.size();

3
4
2
When calling the put method, Java will throw an exception

Q105. What is the problem with this code?

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;


class Main {

    public static void main(String[] args) {
        List<String> list = new ArrayList<String>(Arrays.asList("a", "b", "c"));
        for(String value :list) {
            if(value.equals("a")) {
                list.remove(value);
            }
        }
        System.out.println(list); // outputs [b,c]
    }
}

String should be compared using == method instead of equals.
Modifying a collection while iterating through it can throw a ConcurrentModificationException.
The List interface does not allow an argument of type String to be passed to the remove method.
ArrayList does not implement the List interface.

Q106. How do you convert this method into a lambda expression?

public int square(int x) {
    return x * x;
}

Function<Integer, Integer> squareLambda = (int x) -> { x * x };
Function<Integer, Integer> squareLambda = () -> { return x * x };
Function<Integer, Integer> squareLambda = x -> x * x;
Function<Integer, Integer> squareLambda = x -> return x * x;

Q107. Which choice is a valid implementation of this interface?

interface MyInterface {
    int foo(int x);
}

public class MyClass implements MyInterface {
    // ....
    public void foo(int x){
        System.out.println(x);
    }
}

public class MyClass implements MyInterface {
    // ....
    public double foo(int x){
        return x * 100;
    }
}

public class MyClass implements MyInterface {
    // ....
    public int foo(int x){
        return x * 100;
    }
}

public class MyClass implements MyInterface {
    // ....
    public int foo(){
        return 100;
    }
}

Q108. What is the result of this program?

interface Foo {
    int x = 10;
}

public class Main{

    public static void main(String[] args) {
        Foo.x = 20;
        System.out.println(Foo.x);
    }
}

10
20
null
An error will occur when compiling.

Q109. Which statement must be inserted on line 1 to print the value true?

1:
2: Optional<String> opt = Optional.of(val);
3: System.out.println(opt.isPresent());

Integer val = 15;
String val = "Sam";
String val = null;
Optional<String> val = Optional.empty();

Q110. What will this code print, assuming it is inside the main method of a class?

System.out.println(true && false || true);
System.out.println(false || false && true);

tofauti kati ya makosa na uongo
kweli
kweli
kweli
kweli
tofauti kati ya makosa na uongo
tofauti kati ya makosa na uongo
tofauti kati ya makosa na uongo

Q111. What will this code print?

List<String> list1 = new ArrayList<>();
list1.add("One");
list1.add("Two");
list1.add("Three");

List<String> list2 = new ArrayList<>();
list2.add("Two");

list1.remove(list2);
System.out.println(list1);

[Two]
[One, Two, Three]
[One, Three]
Two

Q112. Which code checks whether the characters in two Strings,jina `time` na `money`, are the same?

if(time <> money){}
if(time.equals(money)){}
if(time == money){}
if(time = money){}

Q113. An _ is a serious issue thrown by the JVM that the JVM is unlikely to recover from. An _ is an unexpected event that an application may be able to deal with to continue execution.

exception,madai
AbnormalException, AccidentalException
kosa, exception
exception, kosa

Q114. Which keyword would not be allowed here?

class Unicorn {
    _____ Unicorn(){}
}

static
mlinzi wa kuongezeka
umma
void

Q115. Which OOP concept is this code an example of?

List[] myLists = {
    new ArrayList<>(),
    new LinkedList<>(),
    new Stack<>(),
    new Vector<>(),
};

for (List list : myLists){
    list.clear();
}

utungaji
generics
polymorphism
encapsulation

Maelezo: Switch between different implementations of the List kiolesura.

Q116. What does this code print?

String a = "bikini";
String b = new String("bikini");
String c = new String("bikini");

System.out.println(a == b);
System.out.println(b == c);

kweli; tofauti kati ya makosa na uongo
tofauti kati ya makosa na uongo; tofauti kati ya makosa na uongo
tofauti kati ya makosa na uongo; kweli
kweli; kweli

Maelezo: == operator compares the object reference. String a = "bikini"; String b = "bikini"; would result in True. Here new creates a new object, so false. Tumia equals() method to compare the content.

Q117. What keyword is added to a method declaration to ensure that two threads do not simultaneously execute it on the same object instance?

asili
tete
synchronized
lock

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q118. Which is a valid type for this lambda function?

_____ oddOrEven = x -> {
    return x % 2 == 0 ? "even" : "odd";
};

Function<Integer, Boolean>
Function<String>
Function<Integer, String>
Function<Integer>

Explaination, Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q119. What is displayed when this code is compiled and executed?

import java.util.HashMap;

public class Main {
    public static void main(String[] args) {
        HashMap<String, Integer> pantry = new HashMap<>();

        pantry.put("Apples", 3);
        pantry.put("Oranges", 2);

        int currentApples = pantry.get("Apples");
        pantry.put("Apples", currentApples + 4);

        System.out.println(pantry.get("Apples"));
    }
}

Maelezo

Q120. What variable type should be declared for capitalization?

List<String> songTitles = Arrays.asList("humble", "element", "dna");
_______ capitalize = (str) -> str.toUpperCase();
songTitles.stream().map(capitalize).forEach(System.out::println);

Function<String, String>
Stream<String>
String<String, String>
Map<String, String>

Maelezo, Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q121. Which is the correct return type for the processFunction method?

_____ processFunction(Integer number, Function<Integer, String> lambda) {
    return lambda.apply(number);
}

Integer
String
Consumer
Function<Integer, String>

Maelezo

Q122. What function could you use to replace slashes for dashes in a list of dates?

List<String> dates = new ArrayList<String>();
// missing code
dates.replaceAll(replaceSlashes);

UnaryOperator<String> replaceSlashes = date -> date.replace("/", "-");
Function<String, String> replaceSlashes = dates -> dates.replace("-", "/");
Map<String, String> replaceSlashes = dates.replace("/", "-");
Consumer<Date> replaceSlashes = date -> date.replace("/", "-");

Maelezo: replaceAll method for any List only accepts UnaryOperator to pass every single element into it then put the result into the List again.

Q123. From which class do all other classes implicitly extend?

Object
Main
Java
Class

Maelezo

Q124. How do you create and run a Thread for this class?

import java.util.date;

public class CurrentDateRunnable implements Runnable {
    @Override
    public void run () {
        while (true) {
            System.out.println("Current date: " + new Date());

            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {
                throw new RuntimeException(e);
            }
        }
    }
}

Thread thread = new Thread(new CurrentDateRunnable()); thread.start();
new Thread(new CurrentDateRunnable()).join();
new CurrentDateRunnable().run();
new CurrentDateRunnable().start();

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Q125. Which expression is a functional equivalent?

List<Integer> numbers = List.of(1,2,3,4);
int total = 0;

for (Integer x : numbers) {
    if (x % 2 == 0)
    total += x * x;
}

int total = numbers.stream()
                        .transform(x -> x * x)
                        .filter(x -> x % 2 == 0)
                        .sum ();

int total = numbers.stream()
                        .filter(x -> x % 2 == 0)
                        .collect(Collectors.toInt());

int total = numbers.stream()
                        .mapToInt (x -> {if (x % 2 == 0) return x * x;})
                        .sum();

int total = numbers.stream()
                        .filter(x -> x % 2 == 0)
                        .mapToInt(x -> x * x)
                        .sum();

Maelezo: The given code in the question will give you the output 20 as total:

numbers                         // Input `List<Integer>` > [1, 2, 3, 4]
    .stream()                   // Converts input into `Stream<Integer>`
    .filter(x -> x % 2 == 0)    // Filter even numbers and return `Stream<Integer>` > [2, 4]
    .mapToInt(x -> x * x)       // Square the number, converts `Integer` to an `int`, and returns `IntStream` > [4, 16]
    .sum()                      // Returns the sum as `int` > 20

Q126. Which is not one of the standard input/output streams provided by java.lang.System?

chapa
out
err
ndani

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Q127. The compiler is complaining about this assignment of the variable pickle to the variable jar. How would you fix this?

double pickle = 2;
int jar = pickle;

Use the method toInt() to convert the pickle before assigning it to the jar.
Cast pickle to an int before assigning it to the jar.
Make pickle into a double by adding + “.0”
Use the new keyword to create a new Integer from pickle before assigning it to the jar.

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q128. What value should x have to make this loop execute 10 nyakati?

for(int i=0; i<30; i+=x) {}

Q129. The _ runs compiled Java code, wakati _ compiles Java files.

Mfumo wa Umwagiliaji wa Smart; JRE
JDK; Mfumo wa Umwagiliaji wa Smart
JRE; JDK
JDK; JRE

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q130. Which packages are part of Java Standard Edition

java.net
java.util
java.lang
All above

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q131. What values for x and y will cause this code to print “btc”?

String buy = "bitcoin";
System.out.println(buy.substring(x, x+1) + buy.substring(y, y+2))

int x = 0; int y = 2;
int x = 1; int y = 3;
int x = 0; int y = 3;
int x = 1; int y = 3;

Q132. Which keyword would you add to make this method the entry point of the program?

public class Main {
    public static void main(String[] args) {
        // Your program logic here
    }
}

exception
args
static
String

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua To make the main method the entry point of the program in Java, we need to use the static keyword. Kwa hivyo, the correct answer is: static The main method must be declared as public static void main(String[] args) to serve as the entry point for a Java program

Q133. You have a list of Bunny objects that you want to sort by weight using Collections.sort. What modification would you make to the Bunny class?

//This is how the original bunny class looks
class Bunny{
    String name;
    int weight;

    Bunny(String name){
        this.name = name;
    }
    public static void main(String args[]){
        Bunny bunny = new Bunny("Bunny 1");
    }
}

Implement the Comparable interface by overriding the compareTo method.
Add the keyword default to the weight variable.
Override the equals method inside the Bunny class.
Implement Sortable and override the sortBy method.

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Q134. Identify the incorrect Java feature.

Object-oriented
Use of pointers
Nguvu
Architectural neural

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q135. What is the output of this code?

int yearsMarried = 2;
switch (yearsMarried) {
   case 1:
      System.out.println("paper");
   case 2:
      System.out.println("cotton");
   case 3:
      System.out.println("leather");
   default:
      System.out.println("I don't gotta buy gifts for nobody!");
}

pamba
pamba
leather
pamba
leather
I don’t gotta buy gifts for nobody!
pamba
I don’t gotta buy gifts for nobody!

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q136. What language features do these expressions demonstrate?

System.out::println
Doggie::fetch

condensed invocation
static references
method references
bad code

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q137. What is the difference between the wait() and sleep() Utafiti wa Harvard unafichua kwa nini kufunga kunaweza kusababisha maisha marefu na yenye afya?

Only Threads can wait, but any Object can be put to sleep.
A waiter can be woken up by another Thread calling notification whereas a sleeper cannot.
When things go wrong, sleep throws an IllegalMonitorStateException whereas wait throws an InterruptedException.
Sleep allows for multi-threading whereas wait does not.

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q138. Which is the right way to declare an enumeration of cats?

enum Cats (SPHYNX, SIAMESE, BENGAL);
enum Cats (“sphynx”, “siamese”, “bengal”);
enum Cats {SPHYNX, SIAMESE, BENGAL}
enum Cats {“sphynx”,”siamese”,”bengal}

Q139. What happens when this code is run?

List<String> horses = new ArrayList<String>();
horses.add (" Sea Biscuit ");
System.out.println(horses.get(1).trim());

“Sea Biscuit” will be printed.
” Sea Biscuit ” will be printed.
An IndexOutOfBoundsException will be thrown.
A NullPointerException will be thrown.

Q140. Which data structure would you choose to associate the amount of rainfall with each month?

Vekta
LinkedList
Ramani
Foleni

Maelezo:

from @yktsang01 in #3915 thread

Map because the map is a key/value pair without creating new classes/objects. So can store the rainfall per month like Map<java.time.Month, Double>. The other options will most likely need some new class to be meaningful:

public class Rainfall {
    private java.time.Month month;
    private double rainfall;
}
Vector<Rainfall>
LinkedList<Rainfall>
Queue<Rainfall>

Q141. Among the following which contains date information?

java.sql timestamp
java.io time
java.io.timestamp
java.sql.time

Q142. What is the size of float and double in Java?

32 na 64
32 na 32
64 na 64
64 na 32

Q143. When you pass an object reference as an argument to a method call what gets passed?

a reference to a copy
a copy of the reference
the object itself
the original reference

Q144. Which choice demonstrates a valid way to create a reference to a static function of another class?

Kazi<Integer, Integer> funcReference = MyClass::myFunction;
Kazi<Integer, Integer> funcReference = MyClass()::myFunction();
Kazi<Integer, Integer> funcReference = MyClass().myFunction;
Kazi<Integer, Integer> funcReference = MyClass.myFunction();

Q145. What is UNICODE?

Unicode is used for the external representation of words and strings
Unicode is used for internal representation of characters and strings
Unicode is used for external representation of characters and strings
Unicode is used for the internal representation of words and strings

Q146. What kind of thread is the Garbage collector thread?

User thread
Daemon thread
Zote mbili
None of these

Q147. What is HashMap and Map?

HashMap is Interface and map is a class that implements that
HashMap is a class and map is an interface that implements that
Map is a class and Hashmap is an interface that implements that
Map is Interface and Hashmap is the class that implements that

Q148. What invokes a thread’s run() njia?

JVM invokes the thread’s run() method when the thread is initially executed.
Main application running the thread.
kuanza() method of the thread class.
None of the above.

Maelezo: After a thread is started, via its start() method of the Thread class, the JVM invokes the thread’s run() method when the thread is initially executed.

Q149. What is true about a final class?

class declared final is a final class.
Final classes are created so the methods implemented by that class cannot be overridden.
It can’t be inherited.
Yote ya hapo juu.

Maelezo: Final classes are created so the methods implemented by that class cannot be overridden. It can’t be inherited. These classes are declared final.

Q150. Which method can be used to find the highest value of x and y?

Math.largest(x,Y)
Math.maxNum(x,Y)
Math.max(x,Y)
Math.maximum(x,Y)

Q151. `void accept(T t)` is method of which Java functional interface?

Consumer
Mzalishaji
Zote mbili
Hakuna

Q152. Which of these does `Stream filter()` operate on?

Predicate
Kiolesura
Class
PLC Object Oriented Programming

Q153. Which of these does `Stream map()` operates on?

Class
Kiolesura
Predicate
Kazi

Q154. What code is needed at line 8?

1: class Main {
2:      public static void main(String[] args) {
3:          Map<String, Integer> map = new HashMap<>();
4:          map.put("a", 1);
5:          map.put("b", 2);
6:          map.put("c", 3);
7:          int result = 0;
8:
9:              result += entry.getValue();
10:         }
11:         System.out.println(result); // outputs 6
12:     }
13: }

Tofauti kuu kati ya(MapEntry<String, Integer> kuingia: map.entrySet()) {
Tofauti kuu kati ya(String entry: ramani) {
Tofauti kuu kati ya(Integer entry: map.values()) {
Tofauti kuu kati ya(Kuingia<String, Integer> kuingia: map.entrySet()) {

Q155. What will print when Lambo is instantiated?

class Car {
    String color = "blue";
}

class Lambo extends Car {
    String color = "white";

    public Lambo() {
        System.out.println(super.color);
        System.out.println(this.color);
        System.out.println(color);
    }
}

blue white white
blue white blue
white white white
white white blue

Q156. Which command will run a FrogSounds app that someone emailed to you as a jar?

jar FrogSounds.java
javac FrogSounds.exe
jar cf FrogSounds.jar
java -jar FrogSounds.jar

Q157. What is the default value of a short variable?

0
0.0
null
undefined

Q158. What will be the output of the following Java program?

class variable_scope {
    public static void main(String args[]) {
        int x;
        x = 5;
        {
            int y = 6;
            System.out.print(x + " " + y);
        }
        System.out.println(x + " " + y);
    }
}

Compilation Error
Runtime Error
5 6 5 6
5 6 5

Maelezo: Scope of variable Y is limited.

Q159. Subclasses of an abstract class are created using the keyword _.

extends
abstracts
violesura
zana

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q160. What will be the output of the following program?

import java.util.Formatter;
public class Course {
    public static void main(String[] args) {
        Formatter data = new Formatter();
        data.format("course %s", "java ");
        System.out.println(data);
        data.format("tutorial %s", "Merit campus");
        System.out.println(data);
    }
}

course java tutorial Merit campus
course java course java tutorial Merit campus
Compilation Error
Runtime Error

Q161. Calculate the time complexity of the following program.

 void printUnorderedPairs(int[] arrayA, int[] arrayB){
    for(int i = 0; i < arrayA.length; i++){
        for(int  j = 0; j < arrayB.length; j++){
            if(arrayA[i] < arrayB[j]){
                System.out.println(arrayA[i] + "," + arrayB[j]);
            }
        }
    }
 }

O(N*N)
O(1)
O(AB)
O(A*B)

Q162. What do these expressions evaluate?

1. true && false
2. true && false || true

1. tofauti kati ya makosa na uongo 2. kweli
1. tofauti kati ya makosa na uongo 2. tofauti kati ya makosa na uongo
1. kweli 2. tofauti kati ya makosa na uongo
1. kweli 2. kweli

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua //check page number 47 and example number 4.:-}

Q163. What allows the programmer to destroy an object x?

1. x.delete()
2. x.finalize()
3. Runtime.getRuntime().gc()
4. Only the garbage collection system can destroy an object.

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua //Hapana, the Garbage Collection can not be forced explicitly. We may request JVM for garbage collection by calling System.gc() njia. But This does not guarantee that JVM will perform the garbage collection

Q164. How many objects are eligible for garbage collection till flag

public class Test
{
    public static void main(String [] args)
    {
        Test obj1 = new Test();
        Test obj2 = m1(obj1);
        Test obj4 = new Test();
        obj2 = obj4;               //Flag
        doComplexStuff();
    }
    static Test m1(Test mx)
    {
        mx = new Test();
        return mx;
    }
}

1. 0
2. 1
3. 2
4. 4

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua // question no 5.

Q165. Which interface definition allows this code to compile

int length = 5;
Square square = x -> x*x;
int a = square.calculate(length);

@FunctionalInterface
public interface Square {
    void calculate(int x);
}

@FunctionalInterface
public interface Square {
    int calculate(int x);
}

@FunctionalInterface
public interface Square {
    int calculate(int... x);
}

@FunctionalInterface
public interface Square {
    void calculate(int x, int y);
}

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q166. Which of the following represents the time complexity of an algorithm?

O(N*N)
O(1)
O(A+B)
O(A*B)

Reasoning: The answer option ‘O(AB)’ should be corrected to ‘O(A*B)’ to accurately represent the time complexity.

O(N*N): This represents a quadratic time complexity, where the running time grows with the square of the input size.
O(1): This represents constant time complexity, indicating that the algorithm’s running time doesn’t depend on the input size.
O(A+B): This represents linear time complexity, indicating that the running time scales linearly with the sum of values A and B.
O(A*B): This represents quadratic time complexity, indicating that the running time scales quadratically with the product of values A and B.

The original answer option 'O(AB)' is incorrect as it does not properly represent a known time complexity notation. The correct notation should be 'O(A*B)' to indicate quadratic time complexity.

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q167. Calculate the space complexity of the following program.

void createArray(int n) {
    int[] arr = new int[n];
    for (int i = 0; i < n; i++) {
        arr[i] = i * 2;
    }
}

O(1)
O(N)
O(N^2)
O(log(N))

//Katika programu hii, an array of size n is created. The space complexity is determined by the size of the dynamic array, which is n. Kwa hiyo, the space complexity is O(N).

Q167. What will be the output of the following Java code?

    import java.util.*;
    public class genericstack <E>
    {
        Stack <E> stk = new Stack <E>();
    public void push(E obj)
        {
            stk.push(obj);
    }
    public E pop()
        {
            E obj = stk.pop();
        return obj;
    }
    }
    class Output
    {
        public static void main(String args[])
        {
            genericstack <String> gs = new genericstack<String>();
            gs.push("Hello");
            System.out.println(gs.pop());
        }
    }

H
Habari
Runtime Error
Compilation Error

//Katika programu hii, The code defines a generic stack class, pushes the string “Habari” onto the stack, and then pops and prints “Habari,” resulting in the output “Hello.”

Q168. In Java, what is the purpose of the synchronized keyword when used in the context of methods or code blocks?

It is used to specify that a method or code block is asynchronous, allowing multiple threads to execute it concurrently.
It is used to mark a method or code block as thread-safe, ensuring that only one thread can execute it at a time.
It indicates that the method or code block is highly optimized for performance and will run faster than non-synchronized methods.
It is used to prevent a method or code block from being executed by any thread, making it effectively “locked.”

Q169. In Java, which of the following statements about the “transient” modifier is true?

Transient variables cannot be accessed outside their declaring class.
Transient variables are automatically initialized with a default value.
Transient variables are not serialized when an object is serialized.
Transient is a keyword used to define inner classes.

Q170. The following prototype shows that a Cylinder subclass is derived from a superclass called Circle.

Class Circle extends Cylinder.
Class Cylinder derived Circle.
Class Cylinder extends Circle.
Class Circle derived Cylinder.

Q171. What will be the output of the following Java code snippet?

class abc
{
    public static void main(String args[])
    {
        if(args.length>0)
        System.out.println(args.length);
    }
}

The snippet compiles and runs but does not print anything.
The snippet compiles, Mafunzo ya VoiceQ kwa Wakurugenzi, and prints 0.
The snippet compiles, Mafunzo ya VoiceQ kwa Wakurugenzi, and prints 1.
The snippet does not compile.

Q172. Which of these classes allows us to define our own formatting pattern for dates and times?

DefinedDateFormat
SimpleDateFormat
ComplexDateFormat
UsersDateFormatRead

Hacks za nyumbani za DIY za kusafisha mfumo wako wa kupumua

Q173.What kind of relationship does extends denote?

is-a
has-a
was-a
uses-a

Mwandishi

Helen Bassey

Okta, I'm Helena, mwandishi wa blogu ambaye ana shauku ya kuchapisha yaliyomo ndani ya niche ya elimu. Ninaamini kuwa elimu ni ufunguo wa maendeleo binafsi na kijamii, na ninataka kushiriki ujuzi na uzoefu wangu na wanafunzi wa umri na asili zote. Kwenye blogi yangu, utapata makala juu ya mada kama vile mikakati ya kujifunza, elimu mtandaoni, mwongozo wa kazi, na zaidi. Pia ninakaribisha maoni na mapendekezo kutoka kwa wasomaji wangu, kwa hivyo jisikie huru kuacha maoni au kuwasiliana nami wakati wowote. Natumai utafurahiya kusoma blogi yangu na unaona kuwa ni muhimu na ya kutia moyo.
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Majibu na maswali ya tathmini ya ustadi wa LinkedIn - Java