Caculator.java
public class Calculator {
private static final char NO_OP = '\0';
private static final char PLUS = '+';
private static final char SUBTRACT = '-';
private static final char MULTIPLY = '*';
private static final char DIVIDE = '/';
private float number1 = 0.0F;
//private float number2 = Float.NaN;
private char operator = NO_OP;
public String opEquals(String number) {
float result;
if ( operator == NO_OP ) {
result = parseNumber(number);
} else {
result = performOperation(parseNumber(number));
}
operator = NO_OP;
number1 = result;
return Float.toString(result);
}
public String opAdd(String number) {
float result;
if ( operator == NO_OP ) {
result = parseNumber(number);
} else {
result = performOperation(parseNumber(number));
}
operator = PLUS;
number1 = result;
return Float.toString(result);
}
public String opSubtract(String number) {
float result;
if ( operator == NO_OP ) {
result = parseNumber(number);
} else {
result = performOperation(parseNumber(number));
}
operator = SUBTRACT;
number1 = result;
return Float.toString(result);
}
public String opMultiply(String number) {
float result;
if ( operator == NO_OP ) {
result = parseNumber(number);
} else {
result = performOperation(parseNumber(number));
}
operator = MULTIPLY;
number1 = result;
return Float.toString(result);
}
public String opDivide(String number) {
float result;
if ( operator == NO_OP ) {
result = parseNumber(number);
} else {
result = performOperation(parseNumber(number));
}
operator = DIVIDE;
number1 = result;
return Float.toString(result);
}
private float performOperation(float number2) {
float result = 0.0F;
switch ( operator ) {
case PLUS:
result = number1 + number2;
break;
case SUBTRACT:
result = number1 - number2;
break;
case MULTIPLY:
result = number1 * number2;
break;
case DIVIDE:
result = number1 / number2;
break;
}
return result;
}
private static float parseNumber(String number) {
float real_number;
try {
real_number = Float.parseFloat(number);
} catch (NumberFormatException e) {
real_number = Float.NaN;
}
return real_number;
}
public static void main(String[] args) {
Calculator calc = new Calculator();
System.out.println("2.0 + >> " + calc.opAdd("2.0"));
System.out.println("3.0 = >> " + calc.opEquals("3.0"));
System.out.println("15.3 * >> " + calc.opMultiply("15.3"));
System.out.println("2.0 / >> " + calc.opDivide("2.0"));
}
}
CalculatorGUI.java
import java.awt.*;
import java.awt.event.*;
public class CalculatorGUI {
// Buttons and a place to put them.
private Button key0, key1, key2, key3, key4;
private Button key5, key6, key7, key8, key9;
private Button keyequal, keyplus, keyminus;
private Button keyperiod, keymult, keydiv;
private Panel buttonArea;
private Label answer; // Where answer will be displayed.
// The model
private Calculator calculator;
private boolean readyForNextNumber;
public CalculatorGUI() {
calculator = new Calculator();
readyForNextNumber = true;
answer = new Label("0.0",Label.RIGHT);
key0 = new Button("0");
key1 = new Button("1");
key2 = new Button("2");
key3 = new Button("3");
key4 = new Button("4");
key5 = new Button("5");
key6 = new Button("6");
key7 = new Button("7");
key8 = new Button("8");
key9 = new Button("9");
keyequal = new Button("=");
keyplus = new Button("+");
keyminus = new Button("-");
keymult = new Button("*");
keydiv = new Button("/");
keyperiod = new Button(".");
buttonArea = new Panel();
}
public void launchFrame() {
buttonArea.setLayout(new GridLayout(4,4));
buttonArea.add(key7);
buttonArea.add(key8);
buttonArea.add(key9);
buttonArea.add(keyplus);
buttonArea.add(key4);
buttonArea.add(key5);
buttonArea.add(key6);
buttonArea.add(keyminus);
buttonArea.add(key1);
buttonArea.add(key2);
buttonArea.add(key3);
buttonArea.add(keymult);
buttonArea.add(key0);
buttonArea.add(keyperiod);
buttonArea.add(keyequal);
buttonArea.add(keydiv);
// Set up event handling
OpButtonHanlder op_handler = new OpButtonHanlder();
NumberButtonHanlder number_handler = new NumberButtonHanlder();
key0.addActionListener(number_handler);
key1.addActionListener(number_handler);
key2.addActionListener(number_handler);
key3.addActionListener(number_handler);
key4.addActionListener(number_handler);
key5.addActionListener(number_handler);
key6.addActionListener(number_handler);
key7.addActionListener(number_handler);
key8.addActionListener(number_handler);
key9.addActionListener(number_handler);
keyperiod.addActionListener(number_handler);
keyplus.addActionListener(op_handler);
keyminus.addActionListener(op_handler);
keymult.addActionListener(op_handler);
keydiv.addActionListener(op_handler);
keyequal.addActionListener(op_handler);
// Create a Frame
Frame f = new Frame("Calculator");
f.addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
f.setSize(200, 200);
f.add(answer, BorderLayout.NORTH);
f.add(buttonArea, BorderLayout.CENTER);
f.setVisible (true);
}
private class OpButtonHanlder implements ActionListener {
public void actionPerformed(ActionEvent event) {
char operator = event.getActionCommand().charAt(0);
String result = "";
switch ( operator ) {
case '+':
result = calculator.opAdd(answer.getText());
break;
case '-':
result = calculator.opSubtract(answer.getText());
break;
case '*':
result = calculator.opMultiply(answer.getText());
break;
case '/':
result = calculator.opDivide(answer.getText());
break;
case '=':
result = calculator.opEquals(answer.getText());
break;
}
answer.setText(result);
readyForNextNumber = true;
}
}
private class NumberButtonHanlder implements ActionListener {
public void actionPerformed(ActionEvent event) {
if ( readyForNextNumber ) {
answer.setText(event.getActionCommand());
readyForNextNumber = false;
} else {
answer.setText(answer.getText() + event.getActionCommand().charAt(0));
}
}
}
public static void main(String args[]) {
CalculatorGUI calcGUI = new CalculatorGUI();
calcGUI.launchFrame();
}
}
两个文件先编译下，然后运行即可。
想学习的朋友讨论下。
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