在策略模式中,可以在运行时更改类行为或其算法.这种类型的设计模式属于行为模式.
在策略模式中,我们创建表示各种策略的对象和根据其策略对象行为不同的上下文对象.策略对象改变了上下文对象的执行算法.
我们将创建一个策略接口定义实现策略接口的操作和具体策略类. Context 是一个使用策略的类.
StrategyPatternDemo ,我们的演示类,将使用 Context 和策略对象,以根据它部署或使用的策略演示Context行为的变化.
创建一个界面.
Strategy.java
public interface Strategy { public int doOperation(int num1, int num2); }
创建实现相同界面的具体类.
OperationAdd.java
public class OperationAdd implements Strategy{ @Override public int doOperation(int num1, int num2) { return num1 + num2; } }
OperationSubstract.java
public class OperationSubstract implements Strategy{ @Override public int doOperation(int num1, int num2) { return num1 - num2; } }
OperationMultiply.java
public class OperationMultiply implements Strategy{ @Override public int doOperation(int num1, int num2) { return num1 * num2; } }
创建上下文 Class.
Context.java
public class Context { private Strategy strategy; public Context(Strategy strategy){ this.strategy = strategy; } public int executeStrategy(int num1, int num2){ return strategy.doOperation(num1, num2); } }
使用上下文改变其策略时的行为变化.
StrategyPatternDemo.java
public class StrategyPatternDemo { public static void main(String[] args) { Context context = new Context(new OperationAdd()); System.out.println("10 + 5 = " + context.executeStrategy(10, 5)); context = new Context(new OperationSubstract()); System.out.println("10 - 5 = " + context.executeStrategy(10, 5)); context = new Context(new OperationMultiply()); System.out.println("10 * 5 = " + context.executeStrategy(10, 5)); } }
验证输出.
10 + 5 = 15 10 - 5 = 5 10 * 5 = 50