Java对象比较

Question

private Comparable[] items = new Comparable[1000000];   

bubbleSort(items);

public static <T extends Comparable<T>> void bubbleSort(T[] list){

    T temp;
    for (int k = 1; k < list.length; k++) {
    // Perform the kth pass
        for (int i = 0; i < list.length - k; i++) {
            if (list[i].compareTo(list[i + 1]) > 0){
                temp = list[i];
                list[i] = list[i + 1];
                list[i + 1] = temp;
            }
        }
    }
}

The problem I'm having is with if (list[i].compareTo(list[i]) > 0) . I've commented everything out, one line at a time. That is the only thing that causes the error, and it doesn't give me any explanation in the output. Just which lines it is. which would be at the if, and calling the bubbleSort method.

Answer 1

private Comparable[] items = new Comparable[1000000];  

This line does not initialize any element in the array. You have null in every slot, hence your NullPointerException .

Or maybe you just didn't post init code, but then the problem would be there.