java单例应用程序，避免程序重复启动，文建锁实现

import java.io.*;
import java.nio.channels.*;

public class Test8 {
	public Test8() {
	}

	public static void main(String args[]) {
		System.out.println("Start application!");
		File f = null;
		RandomAccessFile raf = null;
		FileChannel fc = null;
		FileLock fl = null;
		FileWriter fr = null;
		try {
			f = new File("d:\\a.tmp");
			raf = new RandomAccessFile(f, "rw");
			fr = new FileWriter(f);
			fr.write("singleton");
			fr.close();
			fr = null;
			fc = raf.getChannel();
			fl = fc.tryLock();
		} catch (Exception ex) {
			ex.printStackTrace();
			System.out.println("create file failed!");
			try {
				if (fr != null)
					fr.close();
				if (fl != null)
					fl.release();
				if (fc != null)
					fc.close();
				if (raf != null)
					raf.close();
				if (f != null)
					f.delete();
			} catch (Exception e) {
				e.printStackTrace();
			}
			return;
		}
		System.out.println("start a singleton application!");
		try {
			System.in.read();
		} catch (Exception ex) {
			ex.printStackTrace();
		}
		try {
			if (fr != null)
				fr.close();
			if (fl != null)
				fl.release();
			if (fc != null)
				fc.close();
			if (raf != null)
				raf.close();
			if (f != null)
				f.delete();
		} catch (Exception ex) {
			ex.printStackTrace();
		}
	}
	
	
}

第二次运行时
Start application!
java.io.IOException: 另一个程序已锁定文件的一部分，进程无法访问。
at java.io.FileOutputStream.writeBytes(Native Method)
at java.io.FileOutputStream.write(FileOutputStream.java:260)
at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:202)
at sun.nio.cs.StreamEncoder.implClose(StreamEncoder.java:297)
at sun.nio.cs.StreamEncoder.close(StreamEncoder.java:130)
at java.io.OutputStreamWriter.close(OutputStreamWriter.java:216)
at Test8.main(Test8.java:21)
create file failed!