JAVA单例模式的几种写法

/**

 * 单例模式懒汉式(双重检锁线程安全。JDK1.5之后)

 */

public class Singleton {

    private static volatile Singleton singleton = null;

    private Singleton(){}

    public static Singleton getInstance(){

        if(singleton == null) {

            synchronized(Singleton.class) {

                if(singleton == null) {

                    singleton = new Singleton();

                }

            }

        }

        return singleton;

    }

}

/**

 * 单例模式(内部类写法)

 */

public class Singleton {

    private static class SingletonClass{

        public static final Singleton singleton = new Singleton();

    }

    public static Singleton getInstance(){

        return SingletonClass.singleton;

    }

}

/**

 * 单例模式饿汉式

 * @author Administrator

 *

 */

public class Singleton{

    private static Singleton singleton = new Singleton();

    public static synchronized Singleton getInstance(){

        return singleton;

    }

}