Using String or StringBuffer in Java: which is better?

Question

I read a lot about using StringBuffer and String especially where concatenation is concerned in Java and whether one is thread safe or not.

So, in various Java methods, which should be used?

For example, in a PreparedStatement, should query be a StringBuffer:

    String query = ("SELECT * " +
                    "FROM User " +
                    "WHERE userName = ?;");

    try {
        ps = connection.prepareStatement(query);

And then again, in a String utility methods like:

public static String prefixApostrophesWithBackslash(String stringIn) {
    String stringOut = stringIn.replaceAll("'", "\\\\'");
    return stringOut;
}

And:

 // Removes a char from a String.
public static String removeChar(String stringIn, char c) {
    String stringOut = ("");
    for (int i = 0; i < stringIn.length(); i++) {
        if (stringIn.charAt(i) != c) {
            stringOut += stringIn.charAt(i);
        }
    }
    return stringOut;
}

Should I be using StringBuffers? Especially where repalceAll is not available for such objects anyway.

Thanks

Mr Morgan.

Thanks for all the advice. StringBuffers have been replaced with StringBuilders and Strings replaced with StringBuilders where I've thought it best.

Answer 1

You almost never need to use StringBuffer.

Instead of StringBuffer you probably mean StringBuilder. A StringBuffer is like a StringBuilder except that it also offers thread safety. This thread safety is rarely needed in practice and will just cause your code to run more slowly.

Your question doesn't seem to be about String vs StringBuffer, but about using built-in methods or implementing the code yourself. If there is a built-in method that does exactly what you want, you should probably use it. The chances are it is much better optimized than the code you would write.