exa:
1.獲取兩個字串中最大相同子串。比如：
str1 = “abcwerthelloyuiodef”; str2 = “cvhellobnm”
提示：將短的那個串進行長度依次遞增的子串與較長
的串比較。

public class TestStringContains{
    public static void main(String[] args) {
     String str1="abcwerthelloyuiodef";
     String str2="cvhellobnm";
     //方法一的測試呼叫
   String s=TestStringContains.maxSubstring(str1, str2);
   System.out
 
.println("最大相同字串是："+s);
    //方法二的測試呼叫
   TestStringContains.getsames(str1, str2);
}
      //方法一
        public static String maxSubstring(String str1,String str2){
            while(str2.length() != 1){
                String str3 = str2;
                while(str3.length() != 1){
                    if
 
(!str1.contains(str3)){
                        str3 = str3.substring(0, str3.length()-1);
                    }else{
                        return str3;
                    }
                }
                str2 = str2.substring(1);
            }
            return null;
        }
    //方法二
    public
 
 static void  getsames(String str1,String str2){
        int count = 0;
        String str = "";
        for (int i = 0; i < str2.length(); i++) {
            for (int j = 1; j < str2.length(); j++) {
                if (i < j) {
                    String temStr = str2.substring(i, j);
                    int indexOf = str1.indexOf(temStr);
                    if (indexOf != -1) {
                        if (temStr.length() > count) {
                            count = temStr.length();
                            str = temStr;
                        }
                    }
                }
            }
        }
        System.out.println("最大相同字串是：" + str + ",它長度為：" + count);
        }
    }