java线程安全的单例类

package com.yunshouhu;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;

public class Singleton {

	private static Singleton instance = null;

	private Singleton() {

	}

	public static Singleton getInstance() {
			if (instance == null) {
				synchronized (Singleton.class) {
					
					if(instance==null)
					{
						instance = new Singleton();
					}
					
				}
			}
		return instance;

	}
	
	/* 此处使用一个内部类来维护单例 */  
	private static class SingletonFactory{
		private static Singleton singleton=new Singleton();
	}
	public static Singleton getInstance2()
	{
		return SingletonFactory.singleton;
		
	}
	
  

	public void copyFile(String apth, String bpath) {
		FileInputStream fileInputStream = null;
		FileOutputStream fileOutputStream = null;
		try {
			fileInputStream = new FileInputStream(apth);
			fileOutputStream = new FileOutputStream(bpath);
			byte[] buffer = new byte[4096];// block size是4096B
			int len = -1;
			while ((len = fileInputStream.read(buffer)) != -1) {
				fileOutputStream.write(buffer, 0, len);
			}

		} catch (Exception e) {
			e.printStackTrace();
		} finally {
			try {
				if (fileOutputStream != null) {
					fileOutputStream.flush();
					fileOutputStream.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
			try {
				if (fileInputStream != null)
					fileInputStream.close();
			} catch (IOException e) {
				e.printStackTrace();
			}

		}
	}
	public static void main(String[] args) {
		
		Singleton.getInstance2().copyFile("d:/tool/Oem7F7.exe", "d:/Oem7F7.exe");
		System.out.println("ok");
	}

}

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