[leetcode]Implement strStr()

问题描写叙述：

Implement strStr().

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

代码：

public class Implement_strStr {  //java
	public String strStr(String haystack, String needle) {
		if(haystack == null || needle == null)
            return null;
		int pos = haystack.indexOf(needle);
		if(pos == -1)
			return null;
		return haystack.substring(pos);
    }
}