[Samples] - PropertiesFileWriter

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.Writer;
import java.util.Map.Entry;
import java.util.Properties;

public class PropertiesFileWriter extends BufferedWriter {
	private static final String EXTENSION = "properties";
	private static final String COMMENT_HEADER = "#";
	
	private PropertiesFileWriter(Writer out) throws IOException {
		super(out);
	}
	
	public PropertiesFileWriter(File file) throws IOException, IllegalArgumentException {
		this(new FileWriter(file, false));
	}
	
	public PropertiesFileWriter(File file, boolean append) throws IOException, IllegalArgumentException {
		this(new FileWriter(file, append));
		
		if (!file.getPath().endsWith(EXTENSION)) {
			throw new IllegalArgumentException("Invalid file extension.");
		}
	}
	
	/**
	 * 주석을 추가하고 개행
	 * @param comment
	 * @return
	 * @throws IOException
	 */
	public PropertiesFileWriter commentln(CharSequence comment) throws IOException {
		appendln(COMMENT_HEADER + comment);
		return this;
	}
	
	/**
	 * 내용을 추가하고 개행
	 * @param val
	 * @return
	 * @throws IOException
	 */
	public PropertiesFileWriter appendln(CharSequence val) throws IOException {
		append(val);
		newLine();
		return this;
	}
	
	/**
	 * 내용을 추가하고 개행
	 * @param val
	 * @return
	 * @throws IOException
	 */
	public PropertiesFileWriter writeln(String val) throws IOException {
		write(val);
		newLine();
		return this;
	}
	
	public PropertiesFileWriter writeln(String key, String value) throws IOException {
		write(String.format("%s=%s", key, value));
		newLine();
		return this;
	}
	
	/**
	 * 프로퍼티 내용을 추가하고 개행
	 * @param properties
	 * @return
	 * @throws IOException
	 */
	public PropertiesFileWriter writeln(Properties properties) throws IOException {
		for(Entry<Object, Object> entry : properties.entrySet()) {
			String key = (String) entry.getKey();
			String value = (String) entry.getValue();
			writeln(String.format("%s=%s", key, value));
		}
		return this;
	}
	
	/**
	 * 주석을 달고 프로퍼티 내용을 추가하고 개행
	 * @param comment
	 * @param properties
	 * @return
	 * @throws IOException
	 */
	public PropertiesFileWriter writeln(CharSequence comment, Properties properties) throws IOException {
		commentln(comment);
		writeln(properties);
		return this;
	}
}