設(shè)計模式

裝飾器模式

1. 定義接口

   public interface Component {
       void doSomeThing();
   }
   

2. 具體構(gòu)建角色

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

3. 聲明裝飾器

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

4. 裝飾類的具體實現(xiàn)

   public class ConcratorDecorator1 extends Decorator {
   
       ConcratorDecorator1(Component component) { //必須傳入具體構(gòu)建角色才能夠裝飾
           super(component);
   
       }
       @Override
       public void doSomeThing() { //在保留父類方法的同時拓展新的方法
           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())); //具體構(gòu)建對象new ConreateComponent（）同時具有了裝飾器1和在裝飾器2所提供的拓展方法
   component.doSomeThing(); 
   

單例模式

1. 雙重檢查模式(線程安全)

   class Singleton {
       private volatile static Singleton singleton;
   
       //不允許直接被外部調(diào)用構(gòu)造方法
       private Singleton() {
   
       }
       public static Singleton getSingleton(){
           if (singleton == null) {
               synchronized (Singleton.class) {
                   if (singleton == null) {
                       singleton = new Singleton();
                   }
               }
           }
           return singleton;
       }
   
   }
   

2. 靜態(tài)內(nèi)部類單例模式

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

3. 枚舉單例

   enum Sigleton{
       Instance
   }
   

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