Generating permutations of an int array using java -- error

int temp=input[i];
input[i]=input[startindex];
input[startindex]=temp;
Permute(input, startindex+1);

You've swapped an element before calling Permute but you need to swap it back again afterwards to keep consistent positions of elements across iterations of the for-loop.

This is the best solution I have seen so far :

public static void main(String[] args) {
    int[] a = { 1, 2, 3, 4, 5, 6 };
    permute(0, a);
}

public static void permute(int start, int[] input) {
    if (start == input.length) {
        //System.out.println(input);
        for (int x : input) {
            System.out.print(x);
        }
        System.out.println("");
        return;
    }
    for (int i = start; i < input.length; i++) {
        // swapping
        int temp = input[i];
        input[i] = input[start];
        input[start] = temp;
        // swap(input[i], input[start]);

        permute(start + 1, input);
        // swap(input[i],input[start]);

        int temp2 = input[i];
        input[i] = input[start];
        input[start] = temp2;
    }
}