作为一个初学者 |21xrx.com

作为一个初学者

2023-06-11 07:09:04 深夜i -- --

Java 计算器初学者

作为一个初学者，我一直想学习如何编写一个简易的计算器，最近我学习了Java的基础知识后，终于可以实现我的梦想了。

首先，我需要设计一个用户界面，界面应该包括数字按键、运算符按键、清除键和等于键，通过这些按键来实现计算器的基本功能。

以下是代码示例，您可以将其保存为Calculator.java文件：


import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Calculator extends JFrame implements ActionListener {
  private JButton[] numButtons;
  private JButton[] opButtons;
  private JButton clearButton, equalButton;
  private JTextField displayField;
  private JPanel numPanel, opPanel, buttonPanel;
  private double firstNum, secondNum, result;
  private String operator;
  public Calculator() {
    super("Calculator");
    numButtons = new JButton[10];
    for (int i = 0; i < 10; i++) {
      numButtons[i] = new JButton(String.valueOf(i));
    }
    opButtons = new JButton[4];
    opButtons[0] = new JButton("+");
    opButtons[1] = new JButton("-");
    opButtons[2] = new JButton("*");
    opButtons[3] = new JButton("/");
    clearButton = new JButton("C");
    equalButton = new JButton("=");
    displayField = new JTextField(25);
    numPanel = new JPanel(new GridLayout(4, 3, 5, 5));
    opPanel = new JPanel(new GridLayout(4, 1, 5, 5));
    buttonPanel = new JPanel(new FlowLayout());
    numPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
    opPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
    buttonPanel.setBorder(BorderFactory.createEmptyBorder(5, 5, 5, 5));
    for (int i = 1; i <= 9; i++) {
      numPanel.add(numButtons[i]);
      numButtons[i].addActionListener(this);
    }
    numPanel.add(new JPanel());
    numPanel.add(numButtons[0]);
    numButtons[0].addActionListener(this);
    numPanel.add(new JPanel());
    for (int i = 0; i < 4; i++) {
      opPanel.add(opButtons[i]);
      opButtons[i].addActionListener(this);
    }
    buttonPanel.add(clearButton);
    clearButton.addActionListener(this);
    buttonPanel.add(equalButton);
    equalButton.addActionListener(this);
    getContentPane().setLayout(new BorderLayout());
    getContentPane().add(displayField, BorderLayout.NORTH);
    getContentPane().add(numPanel, BorderLayout.CENTER);
    getContentPane().add(opPanel, BorderLayout.EAST);
    getContentPane().add(buttonPanel, BorderLayout.SOUTH);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    pack();
    setLocationRelativeTo(null);
    setVisible(true);
  }
  public void actionPerformed(ActionEvent e) {
    Object source = e.getSource();
    for (int i = 0; i < 10; i++) {
      if (source == numButtons[i]) {
        displayField.setText(displayField.getText() + i);
        return;
      }
    }
    if (source == opButtons[0]) {
      firstNum = Double.parseDouble(displayField.getText());
      operator = "+";
      displayField.setText("");
    } else if (source == opButtons[1]) {
      firstNum = Double.parseDouble(displayField.getText());
      operator = "-";
      displayField.setText("");
    } else if (source == opButtons[2]) {
      firstNum = Double.parseDouble(displayField.getText());
      operator = "*";
      displayField.setText("");
    } else if (source == opButtons[3]) {
      firstNum = Double.parseDouble(displayField.getText());
      operator = "/";
      displayField.setText("");
    } else if (source == clearButton) {
      displayField.setText("");
    } else if (source == equalButton) {
      secondNum = Double.parseDouble(displayField.getText());
      if (operator.equals("+")) {
        result = firstNum + secondNum;
      } else if (operator.equals("-"))
        result = firstNum - secondNum;
       else if (operator.equals("*")) {
        result = firstNum * secondNum;
      } else if (operator.equals("/"))
        result = firstNum / secondNum;
      
      displayField.setText(String.valueOf(result));
    }
  }
  public static void main(String[] args) {
    new Calculator();
  }
}

在这个例子中，我使用了Java Swing库来定制用户界面。通过实现ActionListener接口，我可以在用户点击按键时捕获事件并响应。当用户点击数字按键时，我将其添加到一个文本框中，运算符按键将获取第一个数字并保存运算符，等于按键将获取第二个数字并计算结果。

通过这个例子，我学会了如何使用Java编写一个简单的计算器，我相信这对于初学者来说是非常有用的。

标题：Java编写简易计算器初学者教程

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