案例2：JAVA GUI 简易计算器

使用javaGUI实现计算器的基本功能，包含一个帮助说明页面，提示用户如何使用。包含一个计算器主界面，要实现基本的加法、减法、乘法、除法运算。

1.帮助界面

 

 

 Help.java

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import java.awt.GridLayout; import java.awt.Toolkit; import java.awt.event.*; import javax.swing.*;   //计算器的实现 public class Help extends JFrame {     JButton btnOK = new JButton("我知道了，开始使用");           public Help() {         super("使用说明");         JLabel lab1 = new JLabel("1.输入第一个操作数");         JLabel lab2= new JLabel("2.选择一个运算符号");         JLabel lab3 = new JLabel("3.输入第二个操作数");         JLabel lab4 = new JLabel("4.点击【计算】按钮进行计算");         JLabel lab5 = new JLabel("5.点击【计算】按钮进行计算");         JLabel lab6 = new JLabel("6.点击【计算】按钮进行计算");           lab1.setBounds(10, 10, 300, 25);         lab2.setBounds(10, 35, 300, 25);         lab3.setBounds(10, 60, 300, 25);         lab4.setBounds(10, 85, 300, 25);         lab5.setBounds(10, 110, 300, 25);         lab6.setBounds(10, 135, 300, 25);                   btnOK.setBounds(30, 160, 200, 25);         btnOK.addActionListener(new ActionListener() {             public void actionPerformed(ActionEvent ee) {                 Calculator c = new Calculator();                 c.CenterPanel();             }         });         JPanel p = new JPanel();         p.setLayout(null);         p.add(lab1);         p.add(lab2);         p.add(lab3);         p.add(lab4);         p.add(lab5);         p.add(lab6);         p.add(btnOK);           getContentPane().add(p);         setSize(380, 250);         setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);         setVisible(true);     }       public static void main(String[] args) {         Help s = new Help();         s.CenterPanel();     }       public void CenterPanel() {         int width = Toolkit.getDefaultToolkit().getScreenSize().width;         int height = Toolkit.getDefaultToolkit().getScreenSize().height;         this.setLocation(width / 2, height / 4);     }       //判断字符串是不是数字     public static boolean isNumeric(String str){         for (int i = str.length();--i>=0;){              if (!Character.isDigit(str.charAt(i))){                 return false;             }         }     return true;     } }

　

2.计算界面

 

 Calculator.java

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import java.awt.GridLayout; import java.awt.Toolkit; import java.awt.event.*; import javax.swing.*;   //计算器的实现 public class Calculator extends JFrame {     JTextField txtNum1 = new JTextField();     JTextField txtNum2 = new JTextField();     JTextField txtResult = new JTextField();     JButton btnCalcul = new JButton("计算");     JButton btnClear = new JButton("清屏");     JButton btnExit = new JButton("退出");           public Calculator() {         super("计算器");         JLabel lab1 = new JLabel("请输入操作数1：");         JLabel lab2= new JLabel("请选择运算符：");         JLabel lab3 = new JLabel("请输入操作数2：");                   final JRadioButton radioButton1=new JRadioButton("加");         final JRadioButton radioButton2=new JRadioButton("减");         final JRadioButton radioButton3=new JRadioButton("乘");         final JRadioButton radioButton4=new JRadioButton("除");         ButtonGroup bg=new ButtonGroup();         bg.add(radioButton1);         bg.add(radioButton2);         bg.add(radioButton3);         bg.add(radioButton4);         JPanel jp1=new JPanel(new GridLayout(1,4));         jp1.add(radioButton1);         jp1.add(radioButton2);         jp1.add(radioButton3);         jp1.add(radioButton4);             JLabel lab4= new JLabel("计算结果：");         lab1.setBounds(10, 10, 100, 25);         lab2.setBounds(10, 40, 100, 25);         lab3.setBounds(10, 70, 100, 25);         lab4.setBounds(10, 100, 100, 25);           txtNum1.setBounds(110, 10, 200, 25);         jp1.setBounds(110, 40, 200, 25);         txtNum2.setBounds(110, 70, 200, 25);         txtResult.setBounds(110, 100, 200, 25);           btnCalcul.setBounds(30, 130, 90, 25);         btnClear.setBounds(130, 130, 90, 25);         btnExit.setBounds(230, 130, 90, 25);         //计算         btnCalcul.addActionListener(new ActionListener() {             public void actionPerformed(ActionEvent ee) {                 String num1=txtNum1.getText().trim();                 String num2=txtNum2.getText().trim();                 String Result="";                 if (!isNumeric(num1)){                 JOptionPane.showMessageDialog(null, "操作数1只允许为数字");                 return;                 }                 if (!isNumeric(num2))                 {                 JOptionPane.showMessageDialog(null, "操作数2只允许为数字");                 return;                 }                 if(radioButton1.isSelected()){                 Result=num1+" + "+num2+" = "+(Integer.parseInt(num1)+Integer.parseInt(num2));                 }                 if(radioButton2.isSelected()){                     Result=num1+" - "+num2+" = "+(Integer.parseInt(num1)-Integer.parseInt(num2));                 }                 if(radioButton3.isSelected()){                     Result=num1+" * "+num2+" = "+(Integer.parseInt(num1)*Integer.parseInt(num2));                 }                 if(radioButton4.isSelected()){                     Result=num1+" / "+num2+" = "+(Integer.parseInt(num1)/Integer.parseInt(num2));                 }                 txtResult.setText(Result);             }         });         //清屏         btnClear.addActionListener(new ActionListener() {             public void actionPerformed(ActionEvent ee) {                 txtNum1.setText("");                 txtNum2.setText("");                 txtResult.setText("");             }         });         //退出程序         btnExit.addActionListener(new ActionListener() {             public void actionPerformed(ActionEvent ee) {                 System.exit(0);             }         });         JPanel p = new JPanel();         p.setLayout(null);         p.add(lab1);         p.add(lab2);         p.add(lab3);         p.add(lab4);           p.add(txtNum1);         p.add(txtNum2);         p.add(jp1);         p.add(txtResult);           p.add(btnCalcul);         p.add(btnClear);         p.add(btnExit);           getContentPane().add(p);         setSize(380, 250);         setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);         setVisible(true);     }       public static void main(String[] args) {         Calculator s = new Calculator();         s.CenterPanel();     }       public void CenterPanel() {         int width = Toolkit.getDefaultToolkit().getScreenSize().width;         int height = Toolkit.getDefaultToolkit().getScreenSize().height;         this.setLocation(width / 2, height / 4);     }       //判断字符串是不是数字     public static boolean isNumeric(String str){         for (int i = str.length();--i>=0;){              if (!Character.isDigit(str.charAt(i))){                 return false;             }         }     return true;     } }