4.txt

一些java的小代码

import java.awt.BorderLayout; 
import java.awt.Color; 
import java.awt.GridLayout; 
import java.awt.event.ActionEvent; 
import java.awt.event.ActionListener; 
import javax.swing.JButton; 
import javax.swing.JFrame; 
import javax.swing.JPanel; 
import javax.swing.JTextField; 

class Calculator extends JFrame implements ActionListener { 

private final String[] KEYS = { "7", "8", "9", "/", "sqrt", "4", "5", "6", 
"*", "%", "1", "2", "3", "-", "1/x", "0", "+/-", ".", "+", "=" }; 
private final String[] COMMAND = { "Backspace", "CE", "C" }; 
private final String[] M = { " ", "MC", "MR", "MS", "M+" }; 
private JButton keys[] = new JButton[KEYS.length]; 
private JButton commands[] = new JButton[COMMAND.length]; 
private JButton m[] = new JButton[M.length]; 
private JTextField resultText = new JTextField("0"); 
private boolean firstDigit = true; 
private double resultNum = 0.0; 
private String operator = "="; 
private boolean operateValidFlag = true; 

public Calculator(){ 
super(); 
init(); 
this.setBackground(Color.LIGHT_GRAY); 
this.setTitle("计算器"); 
this.setLocation(500, 300); 
this.setResizable(false); 
this.pack(); 
} 

private void init() { 

resultText.setHorizontalAlignment(JTextField.RIGHT); 
resultText.setEditable(false); 
resultText.setBackground(Color.WHITE); 
JPanel calckeysPanel = new JPanel(); 
calckeysPanel.setLayout(new GridLayout(4, 5, 3, 3)); 
for (int i = 0; i < KEYS.length; i++) { 
keys[i] = new JButton(KEYS[i]); 
calckeysPanel.add(keys[i]); 
keys[i].setForeground(Color.blue); 
} 
keys[3].setForeground(Color.red); 
keys[8].setForeground(Color.red); 
keys[13].setForeground(Color.red); 
keys[18].setForeground(Color.red); 
keys[19].setForeground(Color.red); 
JPanel commandsPanel = new JPanel(); 
commandsPanel.setLayout(new GridLayout(1, 3, 3, 3)); 
for (int i = 0; i < COMMAND.length; i++) { 
commands[i] = new JButton(COMMAND[i]); 
commandsPanel.add(commands[i]); 
commands[i].setForeground(Color.red); 
} 
JPanel calmsPanel = new JPanel(); 
calmsPanel.setLayout(new GridLayout(5, 1, 3, 3)); 
for (int i = 0; i < M.length; i++) { 
m[i] = new JButton(M[i]); 
calmsPanel.add(m[i]); 
m[i].setForeground(Color.red); 
} 
JPanel panel1 = new JPanel(); 
panel1.setLayout(new BorderLayout(3, 3)); 
panel1.add("North", commandsPanel); 
panel1.add("Center", calckeysPanel); 
JPanel top = new JPanel(); 
top.setLayout(new BorderLayout()); 
top.add("Center", resultText); 
getContentPane().setLayout(new BorderLayout(3, 5)); 
getContentPane().add("North", top); 
getContentPane().add("Center", panel1); 
getContentPane().add("West", calmsPanel); 
for (int i = 0; i < KEYS.length; i++) { 
keys[i].addActionListener(this); 
} 
for (int i = 0; i < COMMAND.length; i++) { 
commands[i].addActionListener(this); 
} 
for (int i = 0; i < M.length; i++) { 
m[i].addActionListener(this); 
} 
} 
public void actionPerformed(ActionEvent e) { 
String label = e.getActionCommand(); 
if (label.equals(COMMAND[0])){ 
handleBackspace(); 
} else if (label.equals(COMMAND[1])) { 
resultText.setText("0"); 
} else if (label.equals(COMMAND[2])){ 
handleC(); 
} else if ("0123456789.".indexOf(label) >= 0) { 
handleNumber(label); 
} else { 
handleOperator(label); 
} 
} 
private void handleBackspace() { 
String text = resultText.getText(); 
int i = text.length(); 
if (i > 0) { 
text = text.substring(0, i - 1); 
if (text.length() == 0) { 
resultText.setText("0"); 
firstDigit = true; 
operator = "="; 
} else { 
resultText.setText(text); 
} 
} 
} 
private void handleNumber(String key) { 
if (firstDigit) { 
resultText.setText(key); 
} else if ((key.equals(".")) && (resultText.getText().indexOf(".") < 0)){ 
resultText.setText(resultText.getText() + "."); 
} else if (!key.equals(".")) { 
resultText.setText(resultText.getText() + key); 
} 
firstDigit = false; 
} 
private void handleC() { 
resultText.setText("0"); 
firstDigit = true; 
operator = "="; 
} 
private void handleOperator(String key) { 
if (operator.equals("/")) { 
if (getNumberFromText() == 0.0){ 
operateValidFlag = false; 
resultText.setText("除数不能为零"); 
} else { 
resultNum /= getNumberFromText(); 
} 
} else if (operator.equals("1/x")) { 
if (resultNum == 0.0){ 
operateValidFlag = false; 
resultText.setText("零没有倒数"); 
} else { 
resultNum = 1 / resultNum; 
} 
} else if (operator.equals("+")){ 
resultNum += getNumberFromText(); 
} else if (operator.equals("-")){ 
resultNum -= getNumberFromText(); 
} else if (operator.equals("*")){ 
resultNum *= getNumberFromText(); 
} else if (operator.equals("sqrt")) { 
resultNum = Math.sqrt(resultNum); 
} else if (operator.equals("%")){ 
resultNum = resultNum / 100; 
} else if (operator.equals("+/-")){ 
resultNum = resultNum * (-1); 
} else if (operator.equals("=")){ 
resultNum = getNumberFromText(); 
} 
if (operateValidFlag) { 
long t1; 
double t2; 
t1 = (long) resultNum; 
t2 = resultNum - t1; 
if (t2 == 0) { 
resultText.setText(String.valueOf(t1)); 
} else { 
resultText.setText(String.valueOf(resultNum)); 
} 
} 
operator = key; 
firstDigit = true; 
operateValidFlag = true; 
} 
private double getNumberFromText() { 
double result = 0; 
try { 
result = Double.valueOf(resultText.getText()).doubleValue(); 
} catch (NumberFormatException e){ 
} 
return result; 
} 

public static void main(String args[]) { 
Calculator calculator1 = new Calculator(); 
calculator1.setVisible(true); 
calculator1.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
} 
}