最长公共子串 暴力法

public static String maxSubString(String s1,String s2){
		String max  =null , min =null;
		max = s1.length() > s2.length() ? s1 : s2 ;
		min = max.equals(s1) ? s2 :s1 ;
		for (int i = 0; i < min.length(); i++) {
			for (int j = 0,k = min.length()-i; k!= min.length()+1; j++,k++) {
				String sub = min.substring(j, k);
				if(max.contains(sub))
					return sub;
			}
		}
		return null;
	}