String运用——查找两个字符串的最大子串

//查找两个字符串的最大子串。

String str1="dsajdwefnadsjaw";
String str2="adwefb";

private static String getMaxSameStr(String str1, String str2) {
        int length1 = str1.length();
        int length2 = str2.length();
        boolean flag=(length1>length2);
        int maxlength=0;
        int first=0;
        int last=0;
        if(flag){
            for(int firstIndex=0;firstIndex<length2;firstIndex++){
                for (int lastIndex=length2-1;lastIndex>firstIndex;lastIndex--){
                    if(str1.contains(str2.substring(firstIndex,lastIndex+1))){
                        if(str2.substring(firstIndex,lastIndex+1).length()>maxlength){
                            maxlength=str2.substring(firstIndex,lastIndex+1).length();
                            first=firstIndex;
                            last=lastIndex+1;
                        }

                    }
                }
            }
            return str2.substring(first,last+1);
        }else{
            first=0;
            last=0;
            for(int firstIndex=0;firstIndex<length1;firstIndex++){
                for (int lastIndex=length1-1;lastIndex>firstIndex;lastIndex--){
                    if(str2.contains(str1.substring(firstIndex,lastIndex+1))){
                        if(str1.substring(firstIndex,lastIndex+1).length()>maxlength){
                            maxlength=str1.substring(firstIndex,lastIndex+1).length();
                            first=firstIndex;
                            last=lastIndex+1;
                        }

                    }
                }
            }
            return str2.substring(first,last+1);
        }
//        return null;
    }