How to Escape Specific Characters Multiple Times in a String Using Java

Question

I have an array of special characters like the following

String[] special = {
        "\", ":", "/"
    };

What I want to be able to do is loop through a given string and if I encounter any of the characters in the special array, I want to add an escape \\ in front of that character. Please see the following input below

Input: Hello : Good : Day
Output Hello \\: Good : Day
Expected: Hello\\:Good\\:Day

As you can see, after it sees the first instance of a special character, it does not check for any other. Any help is appreciated. Code is below

 String[] special = { "\", ":", "/" };

   public String specialCheck(String replaceMe) {

        String cleanMe = replaceMe.replace(" ", "");
        StringBuilder stringBuilder = new StringBuilder(cleanMe);

        for (String badChars : special) {
            if (cleanMe.contains(badChars)) {
                stringBuilder.insert(cleanMe.indexOf(badChars) , "\\\\");
            }
        }

    return stringBuilder.toString();

}

Answer 1

This is a possible answer to your problem.

I made it only using Strings and ArrayLists and it is as simple as possible (Even dumb lol, but it's working).

I don't use StringBuilders because they are mutable and for the case, they are difficult to handle.

Improve it as you wish (I am not using replace(" ", "") by the way), but I saw you may want to use it. Regards.

import java.util.ArrayList;

public class Main {

    public static void main(String[] args) {

        System.out.println(specialCheck("Hello : Good : Day / Test $ for : the @ problem"));
    }


    public static String specialCheck(String replaceMe) {
        String[] special = { "\\", ":", "/", "$", "@"};

        ArrayList<Integer> positions = new ArrayList<Integer>();
        ArrayList<String> phrase = new ArrayList<String>();

        for(int i = 0 ; i < replaceMe.length(); i ++) {
            phrase.add(String.valueOf(replaceMe.charAt(i)));
            for(int j = 0; j < special.length; j++) {
                if(String.valueOf(replaceMe.charAt(i)).equals(special[j].toString())) {
                    positions.add(i);   
                }
            }
        }

        for(int i = 0; i < phrase.size(); i++) {
            for(int j = 0; j < special.length; j++) {
                if(phrase.get(i).equals(special[j])) {
                    phrase.remove(i);
                    phrase.add(i, "\\\\" + special[j] );
                }
            }
        }

        String result = "";
        for(int i = 0; i < phrase.size(); i++) {
            result = result + phrase.get(i);
        }

        return result;

    }
}

Result for the test I made: Hello \\: Good \\: Day \\/ Test \\$ for \\: the \\@ problem

Answer 2

Do it as follows:

public class Main {
    public static void main(String[] args) {
        String str="Hello : Good : Day";
        System.out.println(str.replaceAll(":", "\\\\\\\\:"));
    }
}

Output:

Hello \\: Good \\: Day

Note:

1. Use String:replaceAll to replace all occurrences.
2. Use \\ to escape \

[Update]

Posting the following update based on OP's comment:

public class Main {
    public static void main(String[] args) {
        // Test
        System.out.println(getEscapedString("Hello : Good : Day"));
        System.out.println(getEscapedString("Hello / Good / Day"));
        System.out.println(getEscapedString("Hello \\ Good \\ Day"));
    }

    static String getEscapedString(String str) {
        return str.replaceAll("[:/\\\\]+", "\\\\\\\\$0");
    }
}

Output:

Hello \\: Good \\: Day
Hello \\/ Good \\/ Day
Hello \\\ Good \\\ Day

Answer 3

String result = replaceMe

for( i = 0 ; i < special.length ; i ++)
      result = result.replaceAll(special[i], "////" + special[i]);