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Java计算器程序：打造简洁高效的计算器
2023-06-12 03:58:59 深夜i     23     0
Java 计算器 Swing

Java是一种使用广泛的编程语言，可以用来制作各种应用程序，其中计算器程序是最基本的应用程序之一。本文将介绍如何使用Java语言编写一个简洁高效的计算器程序，并提供相应的代码案例。

首先，在Java中实现计算器程序需要使用Swing库，它是Java图形用户界面（GUI）工具包之一。通过Swing库，我们可以创建各种简单和复杂的GUI元素如按钮、文本框和标签等。下面是一个简单的Java计算器代码示例：

java
package calculator;
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Calculator extends JFrame implements ActionListener {
  private JTextField textField;
  private JButton button1, button2, button3, button4, button5, button6, button7, button8, button9, button0, buttonPlus, buttonMinus, buttonDivide, buttonMultiply, buttonEqual, buttonClear;
  public Calculator() {
    // 设置界面标题
    setTitle("Java Calculator");
    // 创建组件
    textField = new JTextField(20);
    textField.setHorizontalAlignment(JTextField.RIGHT);
    button1 = new JButton("1");
    button2 = new JButton("2");
    button3 = new JButton("3");
    button4 = new JButton("4");
    button5 = new JButton("5");
    button6 = new JButton("6");
    button7 = new JButton("7");
    button8 = new JButton("8");
    button9 = new JButton("9");
    button0 = new JButton("0");
    buttonPlus = new JButton("+");
    buttonMinus = new JButton("-");
    buttonDivide = new JButton("/");
    buttonMultiply = new JButton("*");
    buttonEqual = new JButton("=");
    buttonClear = new JButton("C");
    // 添加事件监听器
    button1.addActionListener(this);
    button2.addActionListener(this);
    button3.addActionListener(this);
    button4.addActionListener(this);
    button5.addActionListener(this);
    button6.addActionListener(this);
    button7.addActionListener(this);
    button8.addActionListener(this);
    button9.addActionListener(this);
    button0.addActionListener(this);
    buttonPlus.addActionListener(this);
    buttonMinus.addActionListener(this);
    buttonDivide.addActionListener(this);
    buttonMultiply.addActionListener(this);
    buttonEqual.addActionListener(this);
    buttonClear.addActionListener(this);
    // 添加组件到界面
    JPanel panel1 = new JPanel(new GridLayout(1, 1, 5, 5));
    panel1.add(textField);
    JPanel panel2 = new JPanel(new GridLayout(4, 4, 5, 5));
    panel2.add(button1);
    panel2.add(button2);
    panel2.add(button3);
    panel2.add(buttonPlus);
    panel2.add(button4);
    panel2.add(button5);
    panel2.add(button6);
    panel2.add(buttonMinus);
    panel2.add(button7);
    panel2.add(button8);
    panel2.add(button9);
    panel2.add(buttonMultiply);
    panel2.add(buttonClear);
    panel2.add(button0);
    panel2.add(buttonEqual);
    panel2.add(buttonDivide);
    add(panel1, BorderLayout.NORTH);
    add(panel2, BorderLayout.CENTER);
    // 设置界面
    setSize(250, 250);
    setVisible(true);
    setResizable(false);
    setLocationRelativeTo(null);
  }
  public void actionPerformed(ActionEvent e) {
    if (e.getSource() == button1) {
      textField.setText(textField.getText() + "1");
    } else if (e.getSource() == button2) {
      textField.setText(textField.getText() + "2");
    } else if (e.getSource() == button3) {
      textField.setText(textField.getText() + "3");
    } else if (e.getSource() == button4) {
      textField.setText(textField.getText() + "4");
    } else if (e.getSource() == button5) {
      textField.setText(textField.getText() + "5");
    } else if (e.getSource() == button6) {
      textField.setText(textField.getText() + "6");
    } else if (e.getSource() == button7) {
      textField.setText(textField.getText() + "7");
    } else if (e.getSource() == button8) {
      textField.setText(textField.getText() + "8");
    } else if (e.getSource() == button9) {
      textField.setText(textField.getText() + "9");
    } else if (e.getSource() == button0) {
      textField.setText(textField.getText() + "0");
    } else if (e.getSource() == buttonPlus) {
      textField.setText(textField.getText() + "+");
    } else if (e.getSource() == buttonMinus) {
      textField.setText(textField.getText() + "-");
    } else if (e.getSource() == buttonDivide) {
      textField.setText(textField.getText() + "/");
    } else if (e.getSource() == buttonMultiply) {
      textField.setText(textField.getText() + "*");
    } else if (e.getSource() == buttonClear) {
      textField.setText("");
    } else if (e.getSource() == buttonEqual) {
      String exp = textField.getText();
      int result = evaluateExpression(exp);
      textField.setText(Integer.toString(result));
    }
  }
  public static void main(String[] args) {
    new Calculator();
  }
  public static int evaluateExpression(String exp) {
    //根据输入的算式求出结果
    return new Object() {
      int pos = -1, ch;
      void nextChar() {
        ch = (++pos < exp.length()) ? exp.charAt(pos) : -1;
      }
      boolean eat(int charToEat) {
        while (ch == ' ') nextChar();
        if (ch == charToEat) {
          nextChar();
          return true;
        }
        return false;
      }
      int parse() {
        nextChar();
        int x = parseExpression();
        if (pos < exp.length()) throw new RuntimeException("Unexpected: " + (char) ch);
        return x;
      }
      int parseExpression() {
        int x = parseTerm();
        for (; ; ) {
          if (eat('+')) x += parseTerm();
          else if (eat('-')) x -= parseTerm();
          else return x;
        }
      }
      int parseTerm() {
        int x = parseFactor();
        for (; ; ) {
          if (eat('*')) x *= parseFactor();
          else if (eat('/')) x /= parseFactor();
          else return x;
        }
      }
      int parseFactor() {
        if (eat('+')) return parseFactor();
        if (eat('-')) return -parseFactor();
        int x;
        int startPos = this.pos;
        if (eat('(')) {
          x = parseExpression();
          eat(')');
        } else if ((ch >= '0' && ch <= '9') || ch == '-') {
          while ((ch >= '0' && ch <= '9') || ch == '-') nextChar();
          x = Integer.parseInt(exp.substring(startPos, this.pos));
        } else {
          throw new RuntimeException("Unexpected: " + (char) ch);
        }
        return x;
      }
    }.parse();
  }
}

在这个示例中，我们创建了一个Calculator类作为程序的主类，继承了JFrame类。我们使用了JTextField、JButton和JPanel等Swing组件，并为每个按钮添加了事件监听器。我们还提供了一个evaluateExpression函数，它使用了递归下降解析器（recursive descent parser）来计算表达式的值。

通过这个程序，我们可以实现一个功能完整的Java计算器，用户可以输入各种算术运算符号和数字，程序将会自动计算结果并显示在文本框中。

  
  

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