两个字符串中最大相同子串

public class StringTest3 {

/**
* 两个字符串中最大相同的子串
*/
public static void main(String[] args) {
String s1="qwertabcyuiop";
String s2="fgabchjkl";
String s=maxCommonSubstring(s1,s2);
System.out.println(s);
}

private static String maxCommonSubstring(String s1, String s2) {
String ss;
String bs;
String sub;
if (s1.length()>s2.length()) {
ss=s2;
bs=s1;
}
else {
ss=s1;
bs=s2;
}
for (int i =0; i <ss.length(); i++) {
for (int j = 0; j < i+1; j++) {
sub=ss.substring(j, ss.length()+j-i);
if(bs.contains(sub)){
return sub;
}
}
}
return null;
}

}