簡易單行計算器，深化學習組合和內部類

面向程序（未優化的代碼）

package GUI.lesson4;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

//簡易計算器
public class TestCal {
    public static void main(String[] args) {
         new Calculator();
    }
}

//計算器類
class Calculator extends Frame{
    public Calculator()  {
        //三個文本框
        TextField num1 = new TextField(10);
        TextField num2 = new TextField(10);
        TextField num3 = new TextField(20);
        //一個按鈕
        Button button = new Button("=");
        button.addActionListener(new MyCalculatorListener(num1,num2,num3));
        //一個標簽
        Label label = new Label("+");
        //布局
        setLayout(new FlowLayout());

        add(num1);
        add(label);
        add(num2);
        add(button);
        add(num3);

        pack();
        setVisible(true);
    }
}

//監聽器類
class MyCalculatorListener implements ActionListener{
    //獲取三個變數
    private TextField num1,num2,num3;

    public MyCalculatorListener(TextField num1,TextField num2,TextField num3) {
        this.num1 = num1;
        this.num2 = num2;
        this.num3 = num3;
    }


    @Override
    public void actionPerformed(ActionEvent e) {
        //1.獲得加數和被加數
        int n1 = Integer.parseInt(num1.getText());//因為getText()中需要輸入字串，所以使用此方法將它變成int值
        int n2 = Integer.parseInt(num2.getText());

        //2.將這個值 +運算后，放到第三個框
        num3.setText(""+(n1+n2));

        //3.清除前兩個框
        num1.setText("");
        num2.setText("");

    }
}

面向物件的方法（第一次優化）

package GUI.lesson4;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

//簡易計算器
public class TestCal {
    public static void main(String[] args) {
         new Calculator().loadFrame();
    }
}

//計算器類
class Calculator extends Frame{

    //屬性
    TextField num1,num2,num3;
    //方法
    public void loadFrame(){
         num1 = new TextField(10);
         num2 = new TextField(10);
         num3 = new TextField(20);
        Button button = new Button("=");
        button.addActionListener(new MyCalculatorListener(this));
        Label label = new Label("+");

        setLayout(new FlowLayout());

        add(num1);
        add(label);
        add(num2);
        add(button);
        add(num3);
        pack();
        setVisible(true);
    }

}

//監聽器類
class MyCalculatorListener implements ActionListener{
    //獲取計算器這個物件,在一個類中組合另外一個類
    Calculator calculator = null;

    public MyCalculatorListener(Calculator calculator) {
       this.calculator = calculator;
    }


    @Override
    public void actionPerformed(ActionEvent e) {
        int n1 = Integer.parseInt(calculator.num1.getText());
        int n2 = Integer.parseInt(calculator.num2.getText());
        calculator.num3.setText(""+(n1+n2));
        calculator.num1.setText("");
        calculator.num2.setText("");


    }
}

完全改造為面向物件（再次優化）

內部類操作：更好的包裝

package GUI.lesson4;

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

//簡易計算器
public class TestCal {
    public static void main(String[] args) {
         new Calculator().loadFrame();
    }
}

//計算器類
class Calculator extends Frame{

    //屬性
    TextField num1,num2,num3;
    //方法
    public void loadFrame(){
         num1 = new TextField(10);
         num2 = new TextField(10);
         num3 = new TextField(20);
        Button button = new Button("=");
        button.addActionListener(new MyCalculatorListener());
        Label label = new Label("+");

        setLayout(new FlowLayout());

        add(num1);
        add(label);
        add(num2);
        add(button);
        add(num3);
        pack();
        setVisible(true);
    }
    //監聽器類
    //內部類最大的好處，就是可以暢通無阻訪問外部類屬性和方法！！
    private class MyCalculatorListener implements ActionListener{

        @Override
        public void actionPerformed(ActionEvent e) {
            int n1 = Integer.parseInt(num1.getText());
            int n2 = Integer.parseInt(num2.getText());
            num3.setText(""+(n1+n2));
            num1.setText("");
            num2.setText("");
        }
    }

}