public String longestCommonStr(String str1, String str2) { int len1 = str1.length(); int len2 = str2.length(); String res = ""; if (len1 < len2) {//默认str1比str2长 String temp = str1; str1 = str2; str2 = temp; } label:for (int len = str2.length(); len > 0 ; len--) { for (int i = 0; i + len < str2.length(); i++) { String subStr = str2.substring(i,i + len); if (str1.contains(subStr)) { res = subStr; break label; } } } return res; }