獲取兩個字符串中最大公約子串。比如“abcwerthelloyuiodefabcdef”和“cvhellobnm”比較

public class StringDemo2 {
    /*
    獲取兩個字符串中最大相同子串。比如：
   str1 = "abcwerthelloyuiodefabcdef";str2 = "cvhellobnm"
   提示：將短的那個串進行長度依次遞減的子串與較長的串比較。

     */
    //前提：兩個字符串中只有一個最大相同子串
    public String getMaxSameString(String str1,String str2){
        if(str1 != null && str2 != null){
            String maxStr = (str1.length() >= str2.length())? str1 : str2;
            String minStr = (str1.length() < str2.length())? str1 : str2;
            int length = minStr.length();

//首尾遞進，尾部先減
            for(int i = 0;i < length;i++){
                for(int x = 0,y = length - i;y <= length;x++,y++){
                    String subStr = minStr.substring(x,y);
                    if(maxStr.contains(subStr)){
                        return subStr;
                    }

                }
            }

        }
        return null;
    }

    // 如果存在多個長度相同的最大相同子串
    // 此時先返回String[]，後面可以用集合中的ArrayList替換，較方便
    public String[] getMaxSameString1(String str1, String str2) {
        if (str1 != null && str2 != null) {
            StringBuffer sBuffer = new StringBuffer();
            String maxString = (str1.length() > str2.length()) ? str1 : str2;
            String minString = (str1.length() > str2.length()) ? str2 : str1;

            int len = minString.length();
            for (int i = 0; i < len; i++) {
                for (int x = 0, y = len - i; y <= len; x++, y++) {
                    String subString = minString.substring(x, y);
                    if (maxString.contains(subString)) {
                        sBuffer.append(subString + ",");
                    }
                }
//                System.out.println(sBuffer);
                if (sBuffer.length() != 0) {
                    break;
                }
            }
            String[] split = sBuffer.toString().replaceAll(",$", "").split("\\,");
            return split;
        }

        return null;
    }

    @Test
    public void testGetMaxSameString(){
        String str1 = "abcwerthello1yuiodefabcdef";
        String str2 = "cvhello1bnmabcdef";
        String[] maxSameStrings = getMaxSameString1(str1, str2);
        System.out.println(Arrays.toString(maxSameStrings));

    }

}