凭借对KMP算法的了解，用java实现了一下，结果和java自带的字符串indexOf比，性能差了十倍。。。

public class KMP {

    private char[] source = {'a','b','c','b','c','a','b','a','b','d','d','e','f','g','h','i','j','a','b','c','a','b','a','b','d','a'};

    private char[] target = {'a','b','c','a','b','a','b','d'};

    private int[] getNextArray(char[] target){
        int[] ret = new int[target.length];
        ret[0] = 0;
        for (int i = 1; i < target.length; i++) {
            int offset = ret[i-1];
            while (offset > 0) {
                if (target[i] == target[offset]) {
                    ret[i] = offset + 1;
                    break;
                } else {
                    offset = ret[offset];
                }
            }
            if (offset == 0 && target[i] == target[0]) {
                ret[i] = 1;
            }
        }
        return ret;
    }

    private int indexOf(int[] next) {
        int offset = 0;
        int i = 0;
        while (i < target.length && offset < source.length) {
            if (target[i] == source[offset]) {
                i++;
                offset++;
            } else if (i == 0) {
                offset++;
            } else {
                i = i - 1 < 0 ? 0 : next[i - 1];
            }
        }
        return offset;
    }

    public static void main(String[] args) {
        KMP k = new KMP();
        long now = System.currentTimeMillis();
        for (int i = 0 ; i < 1000000 ; i++) {
            int[] ret = k.getNextArray(k.target);
            k.indexOf(ret);
        }
        System.out.println(System.currentTimeMillis() - now);
    }

}