Java replace characters in a string except for the given value in a variable

Question

Need some help. So here is the task: Create a program that will ask for a main phrase. Ask for a key string value that will be preserved in the phrase. Display a version of the original main phrase where all chars have been replaced by pluses ("+"), except for appearances of the key string value which are preserved unchanged. Sample outputs:

------------------------------------------------
Enter main phrase: 12xy34
Enter key string:xy
New Version: ++xy++
------------------------------------------------
Enter main phrase: 12xy34
Enter key string:1
New Version: 1+++++
------------------------------------------------
Enter main phrase: 12xy34xyabcxy
Enter key string:xy
New Version: ++xy++xy+++xy

Here is my code:

import java.util.*;
 public class Corpuz_Kervin
{
    public static void main (String [] args)
    {
        Scanner input = new Scanner (System.in);
         String phrase,key= "";
        String plus = "+";


        System.out.print("Enter main phrase : ");
        phrase = input.nextLine();
        System.out.print("Enter key string : ");
        key = input.nextLine();



        for (int i = 0; i < phrase.length(); i++)
        {
            char x = phrase.charAt(i);
            if (x.contains(key))
            {
                System.out.print(phrase.replace(x),"+");
            }
            else 
            {
                System.out.print("Error");
            }
        }
    }
}

Can anyone help me Thanks

Answer 1

使用这个而不是你的循环：

System.out.println(phrase.replaceAll("[^" + key + "]", plus));

Answer 2

为什么不将 replaceAll 与 not phrace 一起使用，请使用此表达式“?!.({您的短语})”

Answer 3

x是一个char ， key是一个String ：条件不应该是x.contains(key) 。