Java Interview Questions and Answers for Freshers

Question 1

Which of these is NOT a primitive type in Java?

Accepted Answer

String. String is a class (an object type); the eight primitives are byte, short, int, long, float, double, char and boolean.

Question 2

What is the default value of an int field in a Java class?

Accepted Answer

0. Fields get default values: 0 for numbers, false for boolean, null for objects. Local variables have no default and must be initialised.

Question 3

Which keyword is used to inherit a class in Java?

Accepted Answer

extends. class B extends A. A class implements interfaces.

Question 4

How many classes can a Java class directly extend?

Accepted Answer

One. Java has single inheritance for classes; use interfaces for multiple types.

Question 5

What does JVM stand for?

Accepted Answer

Java Virtual Machine. The JVM runs compiled bytecode, which is why Java is 'write once, run anywhere'.

Question 6

Which method must every Java application have to start running?

Accepted Answer

public static void main(String[] args). The JVM looks for public static void main(String[] args).

Question 7

What is the difference between == and equals() for Strings?

Accepted Answer

== compares references, equals() compares contents. Two different String objects with the same text are equal() but not ==.

Question 8

Which collection does NOT allow duplicate elements?

Accepted Answer

HashSet. A Set keeps unique elements.

Question 9

What happens when you access index 5 of an array of length 5?

Accepted Answer

ArrayIndexOutOfBoundsException. Valid indexes are 0 to 4; Java checks bounds at run time.

Question 10

Which keyword prevents a method from being overridden?

Accepted Answer

final. A final method can't be overridden; a final class can't be extended.

Question 11

What is method overloading?

Accepted Answer

Same method name with different parameters in one class. Overloading is resolved at compile time; overriding happens in subclasses and is resolved at run time.

Question 12

Which of these is a checked exception?

Accepted Answer

IOException. Checked exceptions must be caught or declared with throws; the others are RuntimeExceptions.

Question 13

Can an interface have a method with a body in Java 8 and later?

Accepted Answer

Yes, default and static methods. Java 8 added default and static methods to interfaces.

Question 14

Why are Java Strings immutable?

Accepted Answer

For security, thread safety and the string pool. Immutable strings can be safely shared and cached in the string pool.

Question 15

Which class should you use to build a long string inside a loop?

Accepted Answer

StringBuilder. StringBuilder appends without creating a new object each time.

Question 16

What does the static keyword mean for a field?

Accepted Answer

One copy is shared by all objects of the class. Static members belong to the class, not to individual objects.

Question 17

Which access modifier makes a member visible only inside its own class?

Accepted Answer

private. private is the most restrictive; protected adds subclasses and the package.

Question 18

What is the time complexity of get(key) in a HashMap on average?

Accepted Answer

O(1). Hashing finds the bucket directly; worst case with many collisions is slower.

Question 19

What is garbage collection in Java?

Accepted Answer

Automatic freeing of objects that are no longer referenced. The JVM reclaims memory automatically; there is no delete in Java.

Question 20

Which keyword refers to the current object inside a method?

Accepted Answer

this. this.name = name; assigns the parameter to the field.

Question 21

What is the parent class of every class in Java?

Accepted Answer

Object. Every class extends java.lang.Object directly or indirectly.

Question 22

Which of these can NOT be instantiated with new?

Accepted Answer

An abstract class. Abstract classes exist to be extended; create objects of their concrete subclasses.

Question 23

What does this code print?
int a = 5, b = 2;
System.out.println(a / b);

Accepted Answer

2. Both operands are int, so / does integer division and drops the .5.

Question 24

What does this code print?
System.out.println("" + 10 + 20);

Accepted Answer

1020. The String comes first, so + joins text: "" + 10 + 20 = "1020".

Question 25

What does this code print?
System.out.println(10 + 20 + "Java");

Accepted Answer

30Java. Evaluated left to right: 10 + 20 = 30 first, then joined with "Java".

Question 26

What does this code print?
String a = "hi";
String b = new String("hi");
System.out.println((a == b) + " " + a.equals(b));

Accepted Answer

false true. new String creates a different object, so == is false; equals() compares the text.

Question 27

What does this code print?
int x = 5;
int y = x++;
System.out.println(y + " " + x);

Accepted Answer

5 6. x++ gives the old value (5) and then increments x to 6.

Question 28

What does this code print?
System.out.println("abc".charAt(1));

Accepted Answer

b. charAt counts from 0: index 1 is 'b'.

Question 29

What does this code print?
int[] a = {1, 2, 3};
System.out.println(a.length);

Accepted Answer

3. length is a field for arrays: {1, 2, 3} has 3 elements.

Question 30

What does this code print?
int n = 2;
switch (n) {
    case 1: System.out.print("One ");
    case 2: System.out.print("Two ");
    case 3: System.out.print("Three"); break;
    default: System.out.print("Default");
}

Accepted Answer

Two Three. There is no break after case 2, so execution falls through into case 3, which does break.

Question 31

What does this code print? java.util.List list = new java.util.ArrayList<>(java.util.List.of(1, 2, 3)); list.remove(1); System.out.println(list);

Accepted Answer

[1, 3]. remove(1) with an int removes the element at index 1 (the value 2).

Question 32

What does this code print?
class Parent { String name() { return "Parent"; } }
class Child extends Parent { String name() { return "Child"; } }
public class Main {
    public static void main(String[] args) {
        Parent p = new Child();
        System.out.println(p.name());
    }
}

Accepted Answer

Child. The object is a Child, so the overridden method runs (runtime polymorphism).

Question 33

What does this code print?
public class Main {
    static String f() {
        try { return "done"; }
        finally { System.out.print("finally "); }
    }
    public static void main(String[] args) {
        System.out.println(f());
    }
}

Accepted Answer

finally done. finally runs before the method returns, even when try has a return.

Question 34

What does this code print?
class Counter {
    static int count = 0;
    Counter() { count++; }
}
public class Main {
    public static void main(String[] args) {
        new Counter();
        new Counter();
        System.out.println(Counter.count);
    }
}

Accepted Answer

2. static count is shared by every Counter object, and two were created.

Question 35

What does this code print?
public class Main {
    static void change(int v) { v = 20; }
    public static void main(String[] args) {
        int x = 10;
        change(x);
        System.out.println(x);
    }
}

Accepted Answer

10. Java passes a copy of the int value; changing it inside the method doesn't affect x.

Question 36

What does this code print?
public class Main {
    static void change(int[] a) { a[0] = 99; }
    public static void main(String[] args) {
        int[] arr = {1, 2};
        change(arr);
        System.out.println(arr[0]);
    }
}

Accepted Answer

99. The array reference is copied, but it points to the same array, so the change is visible.

Question 37

What does this code print?
String s = "java";
String t = s.toUpperCase();
System.out.println(t + " " + s);

Accepted Answer

JAVA java. toUpperCase returns a new String; s itself never changes.

Question 38

What does this code print?
for (int i = 0; i < 3; i++) System.out.print(i + (i < 2 ? " " : ""));

Accepted Answer

0 1 2. The loop prints while i < 3: 0, 1, 2.

Question 39

What does this code print?
System.out.println(5.0 / 0);

Accepted Answer

Infinity. Dividing a double by zero gives Infinity; only integer division by zero throws.

Question 40

What does this code print? java.util.Map m = new java.util.TreeMap<>(); m.put("b", 2); m.put("a", 1); System.out.println(m);

Accepted Answer

{a=1, b=2}. A TreeMap keeps its keys sorted.

Java Interview Questions and Answers for Freshers

Q1. Which of these is NOT a primitive type in Java?

Q2. What is the default value of an int field in a Java class?

Q3. Which keyword is used to inherit a class in Java?

Q4. How many classes can a Java class directly extend?

Q5. What does JVM stand for?

Q6. Which method must every Java application have to start running?

Q7. What is the difference between == and equals() for Strings?

Q8. Which collection does NOT allow duplicate elements?

Q9. What happens when you access index 5 of an array of length 5?

Q10. Which keyword prevents a method from being overridden?

Q11. What is method overloading?

Q12. Which of these is a checked exception?

Q13. Can an interface have a method with a body in Java 8 and later?

Q14. Why are Java Strings immutable?

Q15. Which class should you use to build a long string inside a loop?

Q16. What does the static keyword mean for a field?

Q17. Which access modifier makes a member visible only inside its own class?

Q18. What is the time complexity of get(key) in a HashMap on average?

Q19. What is garbage collection in Java?

Q20. Which keyword refers to the current object inside a method?

Q21. What is the parent class of every class in Java?

Q22. Which of these can NOT be instantiated with new?

Q23. What does this code print?

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