JavaChallenge42

Try to solve the challenge by yourself first!

I got surprised when I saw the bytecode of the above code —

public class JavaChallenge42 {
    public JavaChallenge42() {
    }

    public static void main(String[] args) {
        int[] arr = new int[5];
        int index = 0;
        byte var10001 = index;
        int index = true;
        arr[var10001] = 3;
        System.out.println("The value of first element is " + arr[0]);
        System.out.println("The value of fourth element is " + arr[3]);
    }
}

Before understanding the bytecode, let me tell you the answer which is —

The value of first element is 3
The value of fourth element is 0

Yes, that’s what the answer is. So this challenge is on Java Precedence. Let’s see that —

There are three operators- [], =, = as —

1. arr [index]
2. arr [index]= index
3. index = 3

So according to the precedence table arr[index] has become arr[0] because currently index=0; Now there are 2 = so which one will be evaluated first? So we can get that info from the precedence table itself. In case of = operator the evaluation happens from Right to Left, so now index=3 evaluated first and now the value of the indexis 3 which will be assigned to arr[0] . The value arr[3] is 0 which is a default value of primitive int.