Here is the code I'm using for shacker sort (or bidirectional buble sort). Something is wrong; the error is java.lang.ArrayIndexOutOfBoundsException. Can anybody help me?

public class bidirectional{
    public static void main(String[]args){
        int x[]=new int[]{12,9,4,99,120,1,3,10};
        int j;
        int n=x.length;
        int st=-1;
        while (st<n){
            st++;
            n--;
            for (j=st;j<n;j++) {
                if (x[j]>x[j+1]) {
                    int t=x[j];
                    x[j]=x[j+1];
                    x[j+1]=t;
                }
            }

            for (j=n;--j>=st;) {
                if (x[j]>x[j+1]) {
                    int t=x[j];
                    x[j]=x[j+1];
                    x[j+1]=t;
                }
            }
        }

        for (int k=0;k<x.length;k++) {
            System.out.println(x[k]);
        }
    }
}