设计模式

装饰器模式

1. 定义接口

   public interface Component {
       void doSomeThing();
   }
   

2. 具体构建角色

   public class ConcreateCompnent implements Component {
       @Override
       public void doSomeThing() {
           System.out.println("A功能");
       }
   }
   

3. 声明装饰器

   public class Decorator implements Component {
       private Component component;
   
       Decorator(Component component) { 
           this.component = component;
       }
       @Override
       public void doSomeThing() {
           component.doSomeThing();
       }
   }
   
   

4. 装饰类的具体实现

   public class ConcratorDecorator1 extends Decorator {
   
       ConcratorDecorator1(Component component) { //必须传入具体构建角色才能够装饰
           super(component);
   
       }
       @Override
       public void doSomeThing() { //在保留父类方法的同时拓展新的方法
           super.doSomeThing();
           this.doAnotherThing();
       }
       public void doAnotherThing() { //拓展的新方法
           System.out.println("功能B");
       }
   }
   
   public class ConcratorDecorator2 extends Decorator {
       ConcratorDecorator2(Component component) {
           super(component);
       }
       @Override
       public void doSomeThing() {  
           super.doSomeThing();
           this.doAnotherThing();
   
       }
       public void doAnotherThing() {
           System.out.println("功能C");
       }
   }
   
   

5. Test

   Component component = new ConcratorDecorator2(new ConcratorDecorator1(new ConcreateCompnent())); //具体构建对象new ConreateComponent（）同时具有了装饰器1和在装饰器2所提供的拓展方法
   component.doSomeThing(); 
   

单例模式

1. 双重检查模式(线程安全)

   class Singleton {
       private volatile static Singleton singleton;
   
       //不允许直接被外部调用构造方法
       private Singleton() {
   
       }
       public static Singleton getSingleton(){
           if (singleton == null) {
               synchronized (Singleton.class) {
                   if (singleton == null) {
                       singleton = new Singleton();
                   }
               }
           }
           return singleton;
       }
   
   }
   

2. 静态内部类单例模式

   class Singleton {
       private Singleton() {
   
       }
   
       public static Singleton getInstance() {
           return SingletonHolder.instance;
       }
   
       private static class SingletonHolder {
           private static final Singleton instance = new Singleton();
       }
   }
   

3. 枚举单例

   enum Sigleton{
       Instance
   }
   

持续补充中