Java Coding Interview Questions – Part 6

 
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Java Coding Interview Questions – Part 5

 

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

package quiz;

public class StringCompare {

  public static void main(String[] args) {
  
    String s1 = new String ("Hello");
    String s2 = "Hello";
    
    System.out.println(s1 == s2);
  }

}

 
   

Output

false

  

Note :

== compares the reference and should not be used for String comparison. Rather use methods equals() or equalsIgnoreCase() for string comparison.

  

2. Predict the output of following Java program.

package quiz;

public class StaticQuiz {

  static int a = 5;
  
  static{
    a = a + 5;
  }
  
  static void square(int num){
    System.out.println("Square of " + num + " = " + num*num);
  }

  public static void main(String[] args) {
    int a = 5;
    square(a);
  }

}

    

Output

Square of 5 = 25

 

Explanation

The instance variable value will be used.

 

3. What will be the output of following program ?

public class Varargsquiz {

  public static void main(String[] args) {
    method();
  }

  public static void method(int... v) {
    System.out.println("int");
    for (int n : v)
      System.out.println(n);
  }

  public static void method(boolean... v) {
    System.out.println("bool");
    for (boolean b : v)
      System.out.println(b);
  }
}

  

Output

Compilation error due to ambiguous method

 

Explanation

This will result in a compilation problem because the call method() is ambiguous.. compiler won’t be able to resolve which of the overloaded methods to invoke.

 

4. What happens when you compile and run the following program ?

public class VarargsExample {

  public static void main(String[] args) {
    vaTest(10, 20);
  }

  static void vaTest(int... v) {
    for (int n : v)
      System.out.println(n);
  }

  static void vaTest(int a, int b) {
    System.out.println(a + b);
  }

}

  

Output

30

 

Explanation

The varargs method and the normal method are overloaded. But the method will exact match will be preferred in this case.

 

5. What will be the output of running Class2.java ?

package quiz;

public class Class1 {

  public static void main(String[] args) {
    for (String s : args)
      System.out.print(s);
    System.out.println(4);
  }
}

package quiz;

public class Class2 {

  public static void main(String[] args) {
    String[] numbers = { "1", "2", "3" };
    Class1.main(numbers);
  }
}

  

Output

 

1234

 

Explanation

We can call main() of a class from another class using Classname.main(). Hence, both the print statements will be executed.

 
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Java Coding Interview Questions – Collections

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Java Coding Interview Questions – Part 3

Java Coding Interview Questions – Part 4

 

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