字符串及串的模式匹配

public class Demo01{
    public static void main(String []args){
        String s = "happaaaadwdawdfadfasdfadfgadggasdgadhfjkahsdfjgasjdgfjgjhwguyfguagsyudvfvgvaghdsvfghasvdfyeyfyvayevfyuasyudgfjwebjhfvehgvhgfvawefawefeawppy" ;
        String t = "ppy" ;
        
        long start = System.nanoTime() ;
        
        System.out.println(pusuIndex(s,t));
        
        long end = System.nanoTime();
        System.out.println("代码执行时间："+(end - start)+"ns");
    }
    public static int IndexOf(String str,String t){
        int m = str.length() ;
        int n = t.length() ;
        if(m-n<0)return -1 ;
        
        for(int i=0;i<m-n+1;i++){
            if(str.charAt(i)==t.charAt(0)){
                String temp = str.substring(i,i+n);
                if(temp.equals(t)){
                    return i+1 ;    
                }
            }
        }
        
        return 0 ;
    }
    
    public static int pusuIndex(String s,String t){
        int m = s.length() ;
        int n = t.length() ;
        if(m<n)return -1 ;
        int i = 0 ,j = 0 ;
        while(i<m&&j<n){
            if(s.charAt(i)==t.charAt(j)){
                ++ i ;
                ++ j ;    //j始终是从 0 开始
            }else{
                i = i-j+1 ;
                j = 0 ;    //j又指向t的首位
            }
        }
        if(j==n)return i - n + 1 ;
        else  return 0 ;
    }
}