所以我的任务是设计一个简单的 GUI 计算器,使用堆栈数据结构来执行加法、减法、乘法和除法。计算器窗口应至少有两个面板 - 一个用于显示,另一个用于按钮(0 - 9、. 、+、-、X、/、=、C)。输入表达式后,将显示其后缀或前缀,然后显示结果。
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;
import java.util.Stack;
public class JCalculator implements ActionListener {
JFrame jfrm;
JFrame jfrm2;
JTextField txt;
JLabel results;
String str = "";
Stack operands = new Stack();
char[] a = new char[0];
int used = 0;
JCalculator(){
jfrm = new JFrame("JCalc");
jfrm.getContentPane().setLayout(new GridLayout(0,1));
jfrm.setSize(210,210);
results = new JLabel("",SwingConstants.RIGHT);
jfrm.getContentPane().add(results);
jfrm.setLocation(400,300);
jfrm.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JButton[] calbut= new JButton[14];
String []but = {"7","8","9","/","4","5","6","*","1","2","3","-","0","C"
};
JButton equal = new JButton("=");
JButton add = new JButton("+");
JPanel jbutton = new JPanel();
jbutton.setLayout(new GridLayout(4,3));
for(int i=0; i< but.length;i++){
jbutton.add(calbut[i] = new JButton(but[i]));
calbut[i].addActionListener(this);
}
jbutton.add(equal);
jbutton.add(add);
equal.addActionListener(this);
add.addActionListener(this);
jfrm.getContentPane().add(jbutton);
jfrm.setVisible(true);
}
public void actionPerformed(ActionEvent ae){
char[] a = new char[0];
int used = 0;
if(used == a.length){
char[] newa= new char[a.length + 1];
for(int i = 0; i <used; i++) newa[i]= a[i];
a= newa;
}
if(ae.getActionCommand().equals("1")){
str = results.getText();
results.setText(str + "1");
operands.push(1);
}
if(ae.getActionCommand().equals("2")){
str = results.getText();
results.setText(str + "2");
operands.push(2);
}
if(ae.getActionCommand().equals("3")){
str = results.getText();
results.setText(str + "3");
operands.push(3);
}
if(ae.getActionCommand().equals("4")){
str = results.getText();
results.setText(str + "4");
operands.push(4);
}
if(ae.getActionCommand().equals("5")){
str = results.getText();
results.setText(str + "5");
operands.push(5);
}
if(ae.getActionCommand().equals("6")){
str = results.getText();
results.setText(str + "6");
operands.push(6);
}
if(ae.getActionCommand().equals("7")){
str = results.getText();
results.setText(str + "7");
operands.push(7);
}
if(ae.getActionCommand().equals("8")){
str = results.getText();
results.setText(str + "8");
operands.push(8);
}
if(ae.getActionCommand().equals("9")){
str = results.getText();
results.setText(str + "9");
operands.push(9);
}
if (ae.getActionCommand().equals("0")) {
str = results.getText();
results.setText(str + "0");
operands.push(0);
}
if(ae.getActionCommand().equals("+")){
str = results.getText();
double operand = Double.parseDouble(str);
operands.push(operand);
results.setText("");
a[used]= '+';
used++;
}
if(ae.getActionCommand().equals("-")){
str = results.getText();
double operand = Double.parseDouble(str);
operands.push(operand);
results.setText("");
a[used]= '+';
used++;
}
if(ae.getActionCommand().equals("/")){
str = results.getText();
double operand = Double.parseDouble(str);
operands.push(operand);
results.setText("");
a[used]= '+';
used++;
}
if(ae.getActionCommand().equals("*")){
str = results.getText();
double operand = Double.parseDouble(str);
operands.push(operand);
results.setText("");
a[used]= '*';
used++;
}
if(ae.getActionCommand().equals("=")){
for(int i = 0; i< used; i++){
performBinaryOp(a[i]);
}
str = String.valueOf(operands.pop());
results.setText(str);
}
}
public void performBinaryOp(char nextOperation) {
double leftOperand, rightOperand;
Double result = new Double(0);
rightOperand = (Double) operands.pop();
leftOperand = (Double) operands.pop();
switch (nextOperation) {
case '+':
result = new Double(leftOperand + rightOperand);
break;
case '-':
result = new Double(leftOperand - rightOperand);
break;
case '*':
result = new Double(leftOperand * rightOperand);
break;
case '/':
result = new Double(leftOperand / rightOperand);
break;
}
operands.push(result);
}
public static void main(String[] args)
{
SwingUtilities.invokeLater(new Runnable() {
public void run() {
new JCalculator();
}
});
}
}
我遇到的错误是按下等号按钮时,例如按下 2+3= 它返回第一个值 2.0 然后我收到一条错误消息:
Exception in thread "AWT-EventQueue-0" java.util.EmptyStackException
at java.util.Stack.peek(Unknown Source)
at java.util.Stack.pop(Unknown Source)
at JCalculator.actionPerformed(JCalculator.java:152)
at javax.swing.AbstractButton.fireActionPerformed(Unknown Source)
at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source)
at javax.swing.DefaultButtonModel.setPressed(Unknown Source)
at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source)
at java.awt.Component.processMouseEvent(Unknown Source)
at javax.swing.JComponent.processMouseEvent(Unknown Source)
at java.awt.Component.processEvent(Unknown Source)
at java.awt.Container.processEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source)
at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Window.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$1.run(Unknown Source)
at java.awt.EventQueue$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$2.run(Unknown Source)
at java.awt.EventQueue$2.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessControlContext$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)
我很确定我的问题是我有一个空堆栈,但我不确定代码哪里出错或如何修复它,所以任何帮助将不胜感激。