如何比较两个字符串并用 - 替换不匹配的字母？

Question

I'm trying to write a program to compare two strings, pick out the mismatching bits, and replace them with "-"

ex.) go("boo" , "foo") returns -oo

Here's what I've come up with so far:

String go( String a, String b ) {
  String c = "";
  String q = "-";
  int al = a.length();
  for(int i = 0; i < al; i++){
     char ch = a.charAt(i);
     if(b.indexOf(a)!= -1) {
       c = c + String.valueOf(ch);
     } else {
       c = c + q;
     }
   }
 return c;
 }

Answer 1

Use a StringBuilder in order to quickly and easily mutate a string, and then return the toString() value. You can use setCharAt in order to change the characters at certain indexes.

This code assumes that str1.length() == str2.length() as a pre-condition.

public String escapeDifferentCharacters(String str1, String str2) {
    StringBuilder result = new StringBuilder(str1);
    for (int i = 0; i < str1.length(); i++) {
        if (str1.charAt(i) != str2.charAt(i)) {
            result.setCharAt(i, '-');
        }
    }
    return result.toString();
}

Answer 2

you can do this with regex:

String str1 = "boo";
String str2 = "foo";

System.out.println(str1.replaceAll("[^"+str2+"]","-"));

     (or)

Pattern p = Pattern.compile("[^"+str1+"]");
Matcher m = p.matcher(str2);
System.out.println(m.replaceAll("-"));

output:

-oo