Removing a charAt[i] from a String

Trying to remove all of the characters that are in String S2 from S1. Example would be: S1 = Mississippi River, S2 = is. Return would be S1 and it would be Mpp Rver.

public static String removeLetters(String S1, String S2){
    for(int i=0;i<S1.length();i++){
        for(int j=0;j<S2.length();j++){

            if(S2.charAt(i) == S1.charAt(j))
                S1.charAt(j) = ""; //this does not work but essentially what i want.
        }
    }
}

I have tried 

String S1 = S1.removeAll

and 

S1 = S1.remove

The problem is that remove all takes a String String param and .remove takes a char char, neither of which works. I've fought this for a day, can't get it, any help for noobz? :) thank you all greatly as always.

Jon Skeet
people
quotationmark

One simple approach would be something like:

public static String removeLetters(String source, String lettersToRemove) {
    StringBuilder builder = new StringBuilder();        
    for (int i = 0; i < source.length(); i++) {
        if (lettersToRemove.indexOf(source.charAt(i)) == -1) {
            builder.append(source.charAt(i));
        }
    }
    return builder.toString();
}

Or:

public static String removeLetters(String source, String lettersToRemove) {
    for (int i = 0; i < lettersToRemove.length(); i++) {
        source = source.replace(lettersToRemove.substring(i, i + 1), "");
    }
    return source;
}

While the approaches using regular expressions will work in many cases, you'd need a bit more work to make them robust against things like "-" within lettersToRemove. It really depends on your requirements. (As noted in Sabuj's answer, Pattern.quote may well be enough here... but I'd want to validate that for myself with a few weird cases.)

people

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