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Strings, String Buffers, and String Builders

The Java platform provides three classes String, StringBuffer and StringBuilder which store and manipulate strings — character data consisting of more than one character. Use the following guidelines for deciding which class to use:

• If your text is not going to change, use a string — a String object is immutable.
• If your text will change, and will only be accessed from a single thread, use a string builder.
• If your text will change, and will be accessed from multiple threads, use a string buffer.

Following is a sample program called StringsDemo, which reverses the characters of a string. This program uses both a string and a string builder.

public class StringsDemo {
    public static void main(String[] args) {
        String palindrome = "Dot saw I was Tod";
        int len = palindrome.length();
        StringBuilder dest = new StringBuilder(len);
        for (int i = (len - 1); i >= 0; i--) {
            dest.append(palindrome.charAt(i));
        }
        System.out.format("%s%n", dest.toString());
    }
}

The output from this program is:

doT saw I was toD

The following sections discuss several features of the String, StringBuffer, and StringBuilder classes.

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