Question

Java will be printed 10. can you explain step by step why?
public class WhatsPrinted2 {
    public static void whatHappens(int A[]) {
        int []B = new int[A.length];

        for (int i=0; i<A.length; i++) {
            B[i]=A[i]*2;
        }
        A=B;
    }
    
    public static void main(String args[]) {
        int A[] = {10,20,30};
        whatHappens(A);
        System.out.println(A[0]);
    }
}

will print 10. explain how it's works. Thanks

public class WhatsPrinted3 {
    public static int[] whatHappens(int A[]) {
        int []B = new int[A.length];

        for (int i=0; i<A.length; i++) {
            B[i]=A[i]*2;
        }
        return B;
    }
    
    public static void main(String args[]) {
        int A[] = {10,20,30};
        whatHappens(A);
        System.out.println(A[0]);
    }
}

public class WhatsPrinted4 {
    public static int[] whatHappens(int A[]) {
        int C[]=new int[A.length];
        for (int i=0; i<A.length; i++) {
            C[i]=A[i];
        }
        return C;
    }

    public static void main(String args[]) {
        int A[]={10,20,30};
        int B[]=whatHappens(A);

        if (A==B) {
            System.out.println("equal");
        } else {
            System.out.println("not equal");
        }
    }
}

step by step please. thanks

Answer 1

1.

The program prints 10 because array A is passed as value to the function. So whatever changes made to the array A inside the function will not get reflected in main method

=> printing A[0] in main method will give 10 as 10 is the first element in the actual A

A[0] will be 20 inside the whatHappens function

2.

whatHappens function returns B which is not handled by the main function

=> values of B are not getting reflected to A

If A is assigned with B in main function, then 20 will be printed.

3.

array C is assigned with array A's values and returned which is handled by array B.

In if condition, the address of A and B are checked which is different from each other and produces "Not equal" as the output

values have to be compared to check whether both the arrays are equal.