Arrays.copyOfRange method in java throws incorrect exception

Question

I was working on arrays today and suddenly I came across a scenario throwing unexpected exceptions.

If you look at the code below , I think it must throw ArrayIndexOutOfBoundsException, but surprisingly it is throwing IllegalArgumentException instead:

import java.util.Arrays;
public class RangeTest {
public static void main(String[] args) {
    int[] a = new int[] {0,1,2,3,4,5,6,7,8,9};
    int[] b = Arrays.copyOfRange(a, Integer.MIN_VALUE, 10);
    // If we'll use Integer.MIN_VALUE+100 instead Integer.MIN_VALUE,
    // OutOfMemoryError will be thrown
    for (int k = 0; k < b.length; k++)
        System.out.print(b[k] + " ");
   }
}

Can anybody help me and let me know if I am mistaken?

Answer 1

Well, the Javadoc says :

Throws:

• ArrayIndexOutOfBoundsException - if from < 0 or from > original.length

• IllegalArgumentException - if from > to

Looking at the implementation, you can see that you got an IllegalArgumentException exception instead of ArrayIndexOutOfBoundsException due to int overflow :

public static int[] copyOfRange(int[] original, int from, int to) {
    int newLength = to - from;
    if (newLength < 0)
        throw new IllegalArgumentException(from + " > " + to);
    int[] copy = new int[newLength];
    System.arraycopy(original, from, copy, 0,
                     Math.min(original.length - from, newLength));
    return copy;
}

This code thinks that from > to because to-from caused int overflow (due to from being Integer.MIN_VALUE), which resulted in a negative newLength.