Java编写计算器的常见方法实例总结

package wanwa;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Calculator extends JFrame {
private Container container;
private GridBagLayout layout;
private GridBagConstraints constraints;
private JTextField displayField;// 计算结果显示区
private String lastCommand;// 保存+,-,*,/,=命令
private double result;// 保存计算结果
private boolean start;// 判断是否为数字的开始
public Calculator() {
super("Calculator");
container = getContentPane();
layout = new GridBagLayout();
container.setLayout(layout);
constraints = new GridBagConstraints();
start = true;
result = 0;
lastCommand = "=";
displayField = new JTextField(20);
displayField.setHorizontalAlignment(JTextField.RIGHT);
constraints.gridx = 0;
constraints.gridy = 0;
constraints.gridwidth = 4;
constraints.gridheight = 1;
constraints.fill = GridBagConstraints.BOTH;
constraints.weightx = 100;
constraints.weighty = 100;
layout.setConstraints(displayField, constraints);
container.add(displayField);
ActionListener insert = new InsertAction();
ActionListener command = new CommandAction();
// addButton("Backspace", 0, 1, 2, 1, insert);
// addButton("CE", 2, 1, 1, 1, insert);
// addButton("C", 3, 1, 1, 1, insert);
addButton("7", 0, 2, 1, 1, insert);
addButton("8", 1, 2, 1, 1, insert);
addButton("9", 2, 2, 1, 1, insert);
addButton("/", 3, 2, 1, 1, command);
addButton("4", 0, 3, 1, 1, insert);
addButton("5", 1, 3, 1, 1, insert);
addButton("6", 2, 3, 1, 1, insert);
addButton("*", 3, 3, 1, 1, command);
addButton("1", 0, 4, 1, 1, insert);
addButton("2", 1, 4, 1, 1, insert);
addButton("3", 2, 4, 1, 1, insert);
addButton("-", 3, 4, 1, 1, command);
addButton("0", 0, 5, 1, 1, insert);
// addButton("+/-", 1, 5, 1, 1, insert);// 只显示"-"号,"+"没有实用价值
addButton(".", 2, 5, 1, 1, insert);
addButton("+", 3, 5, 1, 1, command);
addButton("=", 0, 6, 4, 1, command);
this.setResizable(false);
setSize(180, 200);
setVisible(true);
}
private void addButton(String label, int row, int column, int with,
int height, ActionListener listener) {
JButton button = new JButton(label);
constraints.gridx = row;
constraints.gridy = column;
constraints.gridwidth = with;
constraints.gridheight = height;
constraints.fill = GridBagConstraints.BOTH;
button.addActionListener(listener);
layout.setConstraints(button, constraints);
container.add(button);
}
private class InsertAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String input = event.getActionCommand();
if (start) {
displayField.setText("");
start = false;
if (input.equals("+/-"))
displayField.setText(displayField.getText() + "-");
}
if (!input.equals("+/-")) {
  if (input.equals("Backspace")) {
   String str = displayField.getText();
if (str.length() > 0)
  displayField.setText(str.substring(0, str.length() - 1));
} else if (input.equals("CE") || input.equals("C")) {
displayField.setText("0");
start = true;
} else
displayField.setText(displayField.getText() + input);
}
}
}
private class CommandAction implements ActionListener {
 public void actionPerformed(ActionEvent evt) {
 String command = evt.getActionCommand();
 if (start) {
 lastCommand = command;
 } else {
 calculate(Double.parseDouble(displayField.getText()));
 lastCommand = command;
 start = true;
 }
}
}
public void calculate(double x) {
if (lastCommand.equals("+"))
result += x;
else if (lastCommand.equals("-"))
result -= x;
else if (lastCommand.equals("*"))
result *= x;
else if (lastCommand.equals("/"))
result /= x;
else if (lastCommand.equals("="))
result = x;
displayField.setText("" + result);
}
public static void main(String[] args) {
Calculator calculator = new Calculator();
calculator.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}

import java.awt.*;
import java.awt.event.*;
public class MyCalculator {
 PRivate Frame f;
 private TextField tf = new TextField(30);
 private long result;
 private boolean append=false;
 private char Operator='=';
 private Button[] btn=new Button[15];
 public MyCalculator() {
  initComponent();
 }
 private void initComponent() {
  f = new Frame("My Calculator V1.0");
  f.setLayout(new BorderLayout()); //The frame uses BorderLayout
  f.addWindowListener(new WindowAdapter() {
   public void windowClosing(WindowEvent evt) {
    System.exit(0);
   }
  });
  Panel centerPanel = new Panel();
  centerPanel.setLayout(new GridLayout(5, 3)); //The panel uses GridLayout
  NumberListener nl=new NumberListener();
  OperatorListener ol=new OperatorListener();
  btn[10]=new Button("+");
  btn[11]=new Button("-");
  btn[12]=new Button("*");
  btn[13]=new Button("/");
  btn[14]=new Button("=");
  for (int i=0;i<=9;i++){
   btn[i]=new Button(String.valueOf(i));
   centerPanel.add(btn[i]);
   btn[i].addActionListener(nl);
   if (i%2==1){
    centerPanel.add(btn[(i+19)/2]);
    btn[(i+19)/2].addActionListener(ol);
   }
  }
  f.add(centerPanel, BorderLayout.CENTER);
  Panel northPanel = new Panel();
  tf.setEditable(false);
  northPanel.add(tf);
  f.add(northPanel, BorderLayout.NORTH);
 }
 public void go() {
  f.pack();
  f.setVisible(true);
 }
 public static void main(String[] args) {
  new MyCalculator().go();
 }
 /**
 *采用成员内部类方式，实现监听器接口，方便访问主类内类内部成员。
 *此类负责数字按钮Action事件监听和处理
 */
 class NumberListener implements ActionListener{
  public void actionPerformed(ActionEvent e){
   if (!append) {
    tf.setText("");
    append=true;
   }
   String s=tf.getText();
   s+=e.getActionCommand();
   tf.setText(s);
   if (!btn[10].isEnabled()){
    for(int i=10;i<=14;i++) btn[i].setEnabled(true);
   }
  }
 }
 /**
 * 成员内部类，负责操作符按钮的事件处理
 */
 class OperatorListener implements ActionListener{
  public void actionPerformed(ActionEvent e){
   if (!append) return;
   for(int i=10;i<=14;i++) btn[i].setEnabled(false);
   String s=tf.getText();
   long num=Long.parseLong(s);//get the number of textfield
   append=false; //set append
   switch(operator){
    case '+':result+=num;break;
    case '-':result-=num;break;
    case '*':result*=num;break;
    case '/':{
     if (num==0) result=0;
     else result/=num;
     break;
    }
    case '=':result=num;break;
   }
   tf.setText(String.valueOf(result));
   //set the value of result to textfield
   String op=e.getActionCommand();
   operator=op.charAt(0); // set operator
  }
 }
}

package wanwa;
import java.util.*;
public class calc {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("*****************简易计算器****************");
System.out.println("*\t\t\t\t\t*");
System.out.println("* 使用说明： 1.加法 2.减法 3.乘法 4.除法 *");
System.out.println("*\t\t\t\t\t*");
System.out.println("*****************************************");
for(int i=0;i<100;i++){
System.out.print("\n请选择运算规则：");
int num = input.nextInt();
switch(num){
case 1:
System.out.println("\n******你选择了加法******\n");
System.out.print("请输入第1个加数:");
int jiashu1 = input.nextInt();
System.out.print("请输入第2个加数:");
int jiashu2 = input.nextInt();
System.out.println("运算结果为:" + jiashu1 + " + " + jiashu1 + " = " + (jiashu1 + jiashu2));
break;
case 2:
System.out.println("\n******你选择了减法******\n");
System.out.print("请输入被减数:");
int jianshu1 = input.nextInt();
System.out.print("请输入减数:");
int jianshu2 = input.nextInt();
System.out.println("运算结果为:" + jianshu1 + " - " + jianshu2 + " = " + (jianshu1 - jianshu2));
break;
case 3:
System.out.println("\n******你选择了乘法******\n");
System.out.print("请输入第1个因数:");
int chengfa1 = input.nextInt();
System.out.print("请输入第2个因数:");
int chengfa2 = input.nextInt();
System.out.println("运算结果为:" + chengfa1 + " * " + chengfa2 + " = " + (chengfa1 * chengfa2));
break;
case 4:
System.out.println("\n******你选择了除法******\n");
System.out.print("请输入被除数:");
double chufa1 = input.nextInt();
System.out.print("请输入除数:");
double chufa2 = input.nextInt();
System.out.println("运算结果为:" + chufa1 + " / " + chufa2 + " = " + (chufa1 / chufa2) + " 余 " + (chufa1 % chufa2));
break;
default:
System.out.println("\n你的选择有错，请重新选择!");
break;
}
}
}
}

package wanwa;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Calculator extends JFrame {
private Container container;
private GridBagLayout layout;
private GridBagConstraints constraints;
private JTextField displayField;// 计算结果显示区
private String lastCommand;// 保存+,-,*,/,=命令
private double result;// 保存计算结果
private boolean start;// 判断是否为数字的开始
public Calculator() {
super("Calculator");
container = getContentPane();
layout = new GridBagLayout();
container.setLayout(layout);
constraints = new GridBagConstraints();
start = true;
result = 0;
lastCommand = "=";
displayField = new JTextField(20);
displayField.setHorizontalAlignment(JTextField.RIGHT);
constraints.gridx = 0;
constraints.gridy = 0;
constraints.gridwidth = 4;
constraints.gridheight = 1;
constraints.fill = GridBagConstraints.BOTH;
constraints.weightx = 100;
constraints.weighty = 100;
layout.setConstraints(displayField, constraints);
container.add(displayField);
ActionListener insert = new InsertAction();
ActionListener command = new CommandAction();
// addButton("Backspace", 0, 1, 2, 1, insert);
// addButton("CE", 2, 1, 1, 1, insert);
// addButton("C", 3, 1, 1, 1, insert);
addButton("7", 0, 2, 1, 1, insert);
addButton("8", 1, 2, 1, 1, insert);
addButton("9", 2, 2, 1, 1, insert);
addButton("/", 3, 2, 1, 1, command);
addButton("4", 0, 3, 1, 1, insert);
addButton("5", 1, 3, 1, 1, insert);
addButton("6", 2, 3, 1, 1, insert);
addButton("*", 3, 3, 1, 1, command);
addButton("1", 0, 4, 1, 1, insert);
addButton("2", 1, 4, 1, 1, insert);
addButton("3", 2, 4, 1, 1, insert);
addButton("-", 3, 4, 1, 1, command);
addButton("0", 0, 5, 1, 1, insert);
// addButton("+/-", 1, 5, 1, 1, insert);// 只显示"-"号,"+"没有实用价值
addButton(".", 2, 5, 1, 1, insert);
addButton("+", 3, 5, 1, 1, command);
addButton("=", 0, 6, 4, 1, command);
this.setResizable(false);
setSize(180, 200);
setVisible(true);
}
private void addButton(String label, int row, int column, int with,
int height, ActionListener listener) {
JButton button = new JButton(label);
constraints.gridx = row;
constraints.gridy = column;
constraints.gridwidth = with;
constraints.gridheight = height;
constraints.fill = GridBagConstraints.BOTH;
button.addActionListener(listener);
layout.setConstraints(button, constraints);
container.add(button);
}
private class InsertAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String input = event.getActionCommand();
if (start) {
displayField.setText("");
start = false;
if (input.equals("+/-"))
displayField.setText(displayField.getText() + "-");
}
if (!input.equals("+/-")) {
  if (input.equals("Backspace")) {
   String str = displayField.getText();
if (str.length() > 0)
  displayField.setText(str.substring(0, str.length() - 1));
} else if (input.equals("CE") || input.equals("C")) {
displayField.setText("0");
start = true;
} else
displayField.setText(displayField.getText() + input);
}
}
}
private class CommandAction implements ActionListener {
 public void actionPerformed(ActionEvent evt) {
 String command = evt.getActionCommand();
 if (start) {
 lastCommand = command;
 } else {
 calculate(Double.parseDouble(displayField.getText()));
 lastCommand = command;
 start = true;
 }
}
}
public void calculate(double x) {
if (lastCommand.equals("+"))
result += x;
else if (lastCommand.equals("-"))
result -= x;
else if (lastCommand.equals("*"))
result *= x;
else if (lastCommand.equals("/"))
result /= x;
else if (lastCommand.equals("="))
result = x;
displayField.setText("" + result);
}
public static void main(String[] args) {
Calculator calculator = new Calculator();
calculator.setDefaultCloSEOperation(JFrame.EXIT_ON_CLOSE);
}
}