用简单工厂模式实现--简单计算器

uml

有uml图可以看出Client依赖OprationFactory类，而OprationFactory类调用的是Opration接口，

当我们想给计算器增加功能时，修改客户端，增加相应的子类和在OprationFactory类的switch语句中增加相应的case语句即可，

不会影响其他的子类。

使用设计模式主要是提高代码的复用率，通过解耦合，使OprationFactory和Opration类能以后复用。

客户端界面：

package simpleFactory.operation002; import java.awt.*; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; /** * * @author haiyusimon 通过继承和多态来实现各种运算的松耦合， 实现通过简单工厂来产生实例 * */ public class Client extends Frame { private static final long serialVersionUID = -4397773431585170565L; TextField var_a = new TextField(10); TextField var_b = new TextField(10); TextField var_r = new TextField(20); Button jia = new Button("加"); Button jian = new Button("减"); Button cheng = new Button("乘"); Button chu = new Button("除"); public static void main(String args[]) { new Client().launchFrame("计算器"); } /** * @param s */ public void launchFrame(String s) { setTitle(s); setBounds(10, 10, 200, 300); setLayout(new FlowLayout(FlowLayout.LEFT, 10, 10)); add(new Label("第一个数：")); add(var_a); add(new Label("第二个数：")); add(var_b); add(new Label("运算?")); add(jia); add(jian); add(cheng); add(chu); add(new Label("结果：")); add(var_r); pack(); setVisible(true); addWindowListener(new WindowAdapter() { public void windowClosing(WindowEvent e) { System.exit(0); } }); jia.addActionListener(new ClientMonitor('+')); jian.addActionListener(new ClientMonitor('-')); cheng.addActionListener(new ClientMonitor('*')); chu.addActionListener(new ClientMonitor('/')); } private class ClientMonitor implements ActionListener { char coperator = '+'; // 用来判断是哪个按钮 public ClientMonitor(char operator) { this.coperator = operator; } public void actionPerformed(ActionEvent e) { double var_aa = Double.parseDouble(var_a.getText()); double var_ab = Double.parseDouble(var_b.getText()); double r = OperationFactory.createOperation(coperator, var_aa, var_ab); var_r.setText("" + r); } } }

工厂类：

package simpleFactory.operation002; /** * * @author haiyusimon *将由工厂类产生相应的运算类实例 */ public class OperationFactory { public static double createOperation(char operator,double var_aa,double var_ab) { double r = 0.0; Operation operation = new OprationAdd(); //使用接口，把类隐藏在接口下 switch (operator) { case '+': operation = new OprationAdd(); break; //最后必需有break;语句，不然将逐一运行各种情况 case '-': operation = new OprationSub(); break; case '*': operation = new OprationMul(); break; case '/': operation = new OprationDiv(); break; } r = operation.getResult(var_aa, var_ab); return r; } }

运算接口：

package simpleFactory.operation002; public interface Operation { public double getResult(double a,double b); }

加法运算（继承运算接口）：

package simpleFactory.operation002; public class OprationAdd implements Operation { @Override public double getResult(double a, double b) { return a + b; } }

减法运算（继承运算接口）：

package simpleFactory.operation002; public class OprationSub implements Operation { @Override public double getResult(double a, double b) { return a - b; } }

乘法运算（继承运算接口）：

package simpleFactory.operation002; public class OprationMul implements Operation { @Override public double getResult(double a, double b) { return a * b; } }

除法运算（继承运算接口）：

package simpleFactory.operation002; public class OprationDiv implements Operation { @Override public double getResult(double a, double b) { return a / b; } }