KMP算法

public class Main {
/**
* 用于计算匹配的位置（从头到尾）
* @param str
* @param sub
* @return
*/
public static int kmp(String str, String sub) {
if(str == null || sub == null || str.length() == 0 || sub.length() == 0){
throw new IllegalArgumentException("str或者sub不能为空");
}

int j = 0;
int[] n = next(sub);
for (int i = 0; i < str.length(); i++) {
while(j > 0 && str.charAt(i) != sub.charAt(j)){
j = n[j - 1];
}

if(str.charAt(i) == sub.charAt(j)){
j++;
}

if(sub.length() == j){
int index = i - j + 1;
return index;
}
}

return -1;
}//kmp

/**
* 用于生成部分匹配表
* @param sub
* @return
*/
private static int[] next(String sub) {
int[] n = new int[sub.length()];
int x = 0;
for (int i = 1; i < sub.length(); i++) {//i在后面， x在前面

if (sub.charAt(i) == sub.charAt(x)) {
x++;
}

n[i] = x;
}
return n;
}//next

public static void main(String[] args) {
String str = "BBCABEFABCDABA";
String sub = "ABCDAB";

int index = Main.kmp(str, sub);
System.out.println("index-->"+index);
}//main
}


参考： http://blog.csdn.net/cdnight/article/details/11935387 http://blog.csdn.net/qq_26411333/article/details/51622537