package org.apidesign.samples;

import java.util.ArrayList;

import java.util.List;

public class StringBuffer {

    private List<String> all = new ArrayList<String>();

    public StringBuffer() {

        // prevent subclassing from 3rd party code

        if (getClass() != StringBuffer.class && getClass() != StringBufferUnsynch.class) {

            throw new IllegalStateException();

        }

    }

    // BEGIN: string.buffer.factory

    public static StringBuffer createUnsynchronized() {

        return new StringBufferUnsynch();

    }

    // END: string.buffer.factory

    public synchronized StringBuffer append(String s) {

        return appendImpl(s);

    }

    @Override

    public synchronized String toString() {

        return toStringImpl();

    }

    final String toStringImpl() {

        String ret = "";

        for (String s : all) {

            ret += s;

        }

        return ret;

    }

    final StringBuffer appendImpl(String s) {

        all.add(s);

        return this;

    }

    private static final class StringBufferUnsynch extends StringBuffer {

        @Override

        public StringBuffer append(String s) {

            return appendImpl(s);

        }

        @Override

        public String toString() {

            return toStringImpl();

        }

    }

}