解释器模式

解释器模式：通过解析器对象处理一个给定的规则，把复杂的功能分离开，让客户端选择要执行的功能。下面是个小demo，巧妙之处在Context对象的处理上：

package com.jerry.design.interpreter; import java.util.ArrayList; import java.util.List; // 测试类 public class Test { public static void main(String[] args) { String number = "200"; Context context = new Context(number); List<Expression> list = new ArrayList<Expression>(); list.add(new PlusExpression()); list.add(new MinusExpression()); list.add(new MinusExpression()); list.add(new PlusExpression()); list.add(new MinusExpression()); list.add(new MinusExpression()); for(Expression ex : list) { ex.interpret(context); System.out.println(context.getOutput()); } } } class Context { private String input; private int output; public Context(String input) { this.input = input; } public String getInput() { return input; } public void setInput(String input) { this.input = input; } public int getOutput() { return output; } public void setOutput(int output) { this.output = output; } } /* * 抽象解释器 */ abstract class Expression { public abstract void interpret(Context context); } class MinusExpression extends Expression { public void interpret(Context context) { System.out.println("自动递减"); String input = context.getInput(); int inInput = Integer.parseInt(input); --inInput; context.setInput(String.valueOf(inInput)); context.setOutput(inInput); } } class PlusExpression extends Expression { public void interpret(Context context) { System.out.println("自动递增"); String input = context.getInput(); int intInput = Integer.parseInt(input); ++intInput; context.setInput(String.valueOf(intInput)); context.setOutput(intInput); } }