[TOC]

设计模式

一、单例实现

• 懒汉式

  /**
   * 饿汉式，线程安全，调用效率高 ，但是不能延迟加载
   */
  public class Singleton1 {
  
     private static final Singleton1 singleton = new Singleton1();
  
     private Singleton1 () {
     }
  
     public static Singleton1 getInstance() {
        return singleton;
     }
  }
  

• 饿汉式

  /**
   * 懒汉式，线程安全，效率不高，可延迟加载
   */
  public class Singleton {
  
     private static Singleton singleton;
  
     private Singleton() {
     }
  
     public static synchronized Singleton getInstance() {
        if (null == singleton) {
           singleton = new Singleton();
        }
        return singleton;
     }
  }
  

• 枚举实现

  /**
   * 枚举实现单列，线程安全，效率高，但是不能延迟加载
   */
  public class SingletonUseEnum {
  
     private enum  SingletonEnum {
  
        INSTANCE;
         
        private final SingletonUseEnum singleton;
  
        SingletonEnum() {
           singleton = new SingletonUseEnum();
        }
  
        private SingletonUseEnum getInstance() {
           return singleton;
        }
     }
  
     private SingletonUseEnum() {
  
     }
  
     public static SingletonUseEnum getInstance() {
        return SingletonEnum.INSTANCE.getInstance();
     }
  }
  

• 内部类的实现方式

/**
 * 功能描述 <p> 静态内部类实现方式,线程安全，资源利用率高，可以延时加载
 */
public class Singleton3 {

    /**
     * 静态内部类
     */
    private static class SingletonInnerClass {
        public static final Singleton3 instance = new Singleton3();
    }

    private Singleton3 () {

    }

    public static Singleton3 getInstance() {
        return SingletonInnerClass.instance;
    }
}