KMP之next数组求法-java

=nepublic class KMP {
    public static void main(String[] args) {
        String str2 = "abcdassabe";  //{-1,0,0,0,0,1,0,0,1,2}
        int []next =new int[str2.length()];
        new KMP().getNext(str2.toCharArray(),next);
        for (int i : next) {
            System.out.println(i);
        }
    }

    private void getNext(char[] str2, int[] next) {
        int j = -1;  //前缀
        int i = 0;  //后缀
        next[0]=-1;                     //默认初始化3个参数，next[0]=-1  方便回滚                      next[1]=0
        while (i<=str2.length-2){       //退出条件很重要，j给赋值给了后一位的next[i]
            if(j==-1||str2[j]==str2[i]){//2个条件触发前进
                i++;
                j++;
                next[i]=j;//赋值 关系next[i]=j   j=next[j]
            }else {
                j=next[j];//只回滚j
            }
        }
    }
}