策略模式

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// 策略模式 // 定义一个抽象类 public abstract class Strategy {     public abstract void algorithm(); }   // 定义具体的策略 public class ConcreteStrategyA extends Strategy {     public void algorithm() {         System.out.println("使用策略A");     } }   public class ConcreteStrategyB extends Strategy {     public void algorithm() {         System.out.println("使用策略B");     } }   // 定义上下文类 public class Context {     private Strategy strategy;       public Context(Strategy strategy) {         this.strategy = strategy;     }       public void executeAlgorithm() {         strategy.algorithm();     } }   // 测试类 public class Test {     public static void main(String[] args) {         Context context;           context = new Context(new ConcreteStrategyA());         context.executeAlgorithm();           context = new Context(new ConcreteStrategyB());         context.executeAlgorithm();     } }