LeetCode3.2 @ Implement strStr() D4F5

Implement strStr().

Returns a pointer to the first occurrence of needle in haystack, or null if needle is not part of haystack.

Wiki：A Needle in a haystack is a figure of speech used to refer to something that is difficult to locate in a much larger space.

来源于http://blog.youkuaiyun.com/linhuanmars/article/details/20276833

注意总结：：

【模型】两个字符串或数组，注意for循环的写法

public class Solution {
    public String strStr(String haystack, String needle) {  
        if(haystack==null || needle==null || needle.length()==0)
            return haystack;
        if(haystack.length()<needle.length())
            return null;
        for(int i=0;i<=haystack.length()-needle.length();i++){
            boolean successFlag=true;
            for(int j=0;j<needle.length();j++){
                if(haystack.charAt(i+j)!=needle.charAt(j)){
                    successFlag=false;
                    break;
                }
            }
            if(successFlag)
                return haystack.substring(i);
        }
        return null;
    }  
}