KMP快速模式匹配的java实现

/**
*
* @author Vincent
*
*/
public class PatternMap {
private String pat; //模式
private int [] f; //模式对应的失败函数
private String source; //目标
PatternMap(String p,String s){ pat=p;source=s;f=new int[pat.length()];  }
int KMP_FastFind(){
Fail();
int p=0,s=0;
int m=pat.length(),n=source.length();
while(p<m&&s<n){
if(pat.charAt(p)==source.charAt(s)){
p++;s++;
}
else if(p==0)s++;
else
p=f[p-1]+1;
}
if(p<m)
return -1;
return s-m; //下标从0开始
}
void Fail(){
int m=pat.length();
f[0]=-1;
int i=0;
for(int j=1;j<m;j++){
i=f[j-1];
while( (pat.charAt(j)!=pat.charAt(i+1)) && (i>0) ){
i=f[i];
}
if(pat.charAt(j)==pat.charAt(i+1)){
f[j]=i+1;
}
else f[j]=-1;
}
}
public static void main(String[] args){
PatternMap pm=new PatternMap("vince_iamvincent","vincevince_iamvincentaaa");
System.out.println(pm.KMP_FastFind());
/*
* print 失败函数
*/
int m=pm.pat.length();
for(int i=0;i<m;i++){
System.out.println(pm.f[i]);
}
}
}