用java编程加减乘除计算器

　　刚好用设计模式（简单工厂模式）编写了一个计算器。

package com.medavis.simplefactory.ui;

import java.util.Scanner;

import com.medavis.simplefactory.operate.OperatorFactory;

public class CaculatorUI {

    private static Scanner sc;

    public static void main(String[] args) {
        
        try {
            System.out.println("Please input a number:");
            
            sc = new Scanner(System.in);
            
            long first = sc.nextLong();
            
            System.out.println("Please input a operational character (+-*/):");
            
            sc = new Scanner(System.in);
            
            String operator = sc.nextLine();
            
            System.out.println("Please input a number:");
            
            sc = new Scanner(System.in);
            
            long second = sc.nextLong();
            
            OperatorFactory opf=new OperatorFactory();
            
            System.out.println(first + operator + second + "=" + opf.getOperator(operator).getResult(first, second));
            
        } catch(Exception e) {
            
            System.out.println("Your input is wrong!");
            
        }
    }
}



package com.medavis.simplefactory.operate;


public class OperatorAdd extends Operator{

    @Override
    public long getResult(long first, long second) {
        
        return first+second;
        
    }
}
package com.medavis.simplefactory.operate;


public class OperatorDiv  extends Operator{

    @Override
    public long getResult(long first, long second) {
        
        return first/second;
        
    }
}

package com.medavis.simplefactory.operate;


public class OperatorFactory {

    public Operator getOperator(String operator) throws Exception{
        switch(operator){
        case "+":
            return new OperatorAdd();
        case "-":
            return new OperatorSub();
        case "*":
            return new OperatorMul();
        case "/":
            return new OperatorDiv();
        default:
             throw new Exception(); 
        }
    }

}


package com.medavis.simplefactory.operate;


public class OperatorMul  extends Operator {

    @Override
    public long getResult(long first, long second) {
        
        return first*second;
        
    }
}

package com.medavis.simplefactory.operate;


public class OperatorSub  extends Operator{
    
    @Override
    public long getResult(long first, long second) {
        
        return first-second;
        
    }
}

可以用if else语句

用switch更简单，代码也清晰，用switch吧
声明一个表示运算符号的变量（op）

switch(op){
case:"+"
...
break;

}

就这样写吧

import java.awt.*;
import java.awt.event.*;

class JiSuanQi implements ActionListener {
Frame f = new Frame("计算器");

Panel p = new Panel();

Panel p1 = new Panel();

Panel p2 = new Panel();

Button b = new Button("x+y");

Button b1 = new Button("x-y");

Button b2 = new Button("清除");

Label Lbx = new Label("x");

Label lby = new Label("y");

TextField tfx = new TextField(4);

TextField tfy = new TextField(4);

TextArea ta = new TextArea();

Font ft = new Font("宋体", Font.BOLD, 18);

GridLayout g1 = new GridLayout(4, 1);

GridLayout g2 = new GridLayout(4, 1);

double x, y, sum;

public static void main(String[] args) {
JiSuanQi ji = new JiSuanQi();
ji.go();
}

public void go() {
b.setFont(ft);
b1.setFont(ft);
b2.setFont(ft);
Lbx.setAlignment(Label.CENTER); //Lbx
lby.setAlignment(Label.CENTER);
Lbx.setFont(ft);
lby.setFont(ft);
tfx.setFont(ft);
tfy.setFont(ft);
ta.setFont(ft);
p.setLayout(g1);
p.add(Lbx);
p.add(tfx);
p.add(lby);
p.add(tfy);
f.add(p, "West");
p1.setLayout(g2);
p1.add(b);
p1.add(b1);
b.addActionListener(this);
b1.addActionListener(this);
f.add(p1, "East");
p2.add(b2);
b2.addActionListener(this);
f.add(p2, "South");
f.add(ta, "Center");
f.setSize(250, 150);
f.setVisible(true);
}

public void actionPerformed(ActionEvent ae) {

String s = ae.getActionCommand();
x = Double.parseDouble(tfx.getText());
y = Double.parseDouble(tfy.getText());
if (s.equals("x+y") == true) {
ta.append("x+y" + (x + y) + "\n");
}
if (s.equals("x-y") == true) {
ta.append("x-y" + (x - y) + "\n");
}
if (s.equals("清除") == true) {
ta.setText("");
}
}