Problems with Java Arrays.sort() on sub-arrays -- is this a bug?

Question

I have noticed odd behavior when using Java Arrays.sort() on sub-arrays. Here is a demo program. Is this a bug in Java?

package sorted_subsegments;

import java.util.Arrays;

public class sortTest {
    public static void main(String[] args) {
        int A[] = {3, 2, 1};
        System.out.format("A: %s\n", Arrays.toString(A));
        Arrays.sort(A, 0, 1);
        System.out.format(" after sub array sort on A: %s\n", Arrays.toString(A));
        System.out.println("Should be A: [2, 3, 1]");
        Arrays.sort(A);
        System.out.format(" whole array sort on A: %s\n", Arrays.toString(A));
    }
}

Answer 1

From the Javadoc

fromIndex - the index of the first element, inclusive, to be sorted

toIndex - the index of the last element, exclusive, to be sorted

The second index (toIndex) is NOT included in the range to be sorted.

So, in your example

Arrays.sort(A, 0, 1);

you are sorting only element [0] of the array, which does nothing.