最近在学习数据结构,学到Stack栈,想到用栈求表达式的值.为了看起来更好看一点,就写了一个GUI界面.
package MyCalculator;
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Font;
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;
import javax.swing.border.Border;
public class MyCalc {
public static void main(String[] args) {
new myFrame("TWY计算器");
}
}
class myFrame extends JFrame {
JTextField text = new JTextField();
JButton[] bt = new JButton[20];
String key[] = new String[] { "ans", "del", "EC", "C", "1", "2", "3", "+", "4", "5", "6", "-", "7", "8", "9", "*",
"0", ".", "=", "/" };
JPanel keyPanel = new JPanel();
boolean finish = false;
double ans=0;
public myFrame(String title) {
super(title);
init();
}
public void init() {
text.setHorizontalAlignment(JTextField.RIGHT);
text.setPreferredSize(new Dimension(0, 40));
text.setFont(new Font("宋体", Font.BOLD, 20));
for (int i = 0; i < bt.length; i++) {
bt[i] = new JButton(key[i]);
}
Container pane = this.getContentPane();
this.add(text, BorderLayout.NORTH);
keyPanel.setLayout(new GridLayout(5, 4, 3, 3));
this.add(keyPanel, BorderLayout.CENTER);
for (int i = 0; i < bt.length; i++) {
keyPanel.add(bt[i]);
bt[i].addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
if (finish == true) {
text.setText("");
finish = false;
}
String command = e.getActionCommand();
String s = text.getText();
if ("0123456789.+-*/".indexOf(command) >= 0)
text.setText(text.getText() + command);
else if (command.equals("del"))
text.setText(s.substring(0, s.length() - 1));
else if (command.equals("C") || command.equals("EC"))
text.setText("");
else if (command.equals("ans") )
text.setText(text.getText() + ans);
else if (command.equals("=")) {
ans=new calc(s).result;
text.setText(text.getText() + "="+ans);
finish = true;
}
}
});
}
this.setVisible(true);
this.setLocation(500, 200);
this.setSize(325, 325);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
package MyCalculator;
import java.util.Stack;
class calc {
Stack<String> ops = new Stack<String>();
Stack<Double> num = new Stack<Double>();
String exp;
double result;
public calc(String s) {
exp = s;
calctor();
}
public void calctor() {
String s[] = tranform(exp).split(" ");
for (String string : s) {
if (string.matches("\\d+") || string.matches("\\d+.\\d+")) {
double n = Double.parseDouble(string);
num.push(n);
} else if (string.equals("+") || string.equals("-") || string.equals("/") || string.equals("*")) {
double op1 = num.pop(), op2 = num.pop();
switch (string) {
case "+":
num.push(op1 + op2);
break;
case "-":
num.push(op2 - op1);
break;
case "*":
num.push(op2 * op1);
break;
case "/":
num.push(op2 / op1);
break;
default:
break;
}
} else {
}
}
result = num.peek();
// System.out.println("ans= " + result);
}
public String tranform(String s) {
s = s.replace("+", " + ");
s = s.replace("-", " - ");
s = s.replace("*", " * ");
s = s.replace("/", " / ");
String str[] = s.split(" ");
String s1 = "";
for (String string : str) {
if (string.matches("\\d+") || string.matches("\\d+.\\d+")) {
s1 = s1 + " " + string;
} else {
if (ops.isEmpty()) {
ops.push(string);
continue;// 跳过下面
}
String temp = ops.peek();
while (priority(temp) >= priority(string)) {// 栈顶元素优先级高于或等于进栈元素,不断弹出栈顶元素
s1 = s1 + " " + temp;
ops.pop();
if (ops.isEmpty())
break;
temp = ops.peek();
}
ops.push(string);
}
}
while (!ops.isEmpty())
s1 = s1 + " " + ops.pop();
// System.out.println(s1);
return s1;
}
public int priority(String s) {
switch (s) {
case "+":
case "-":
return 1;
case "*":
case "/":
return 2;
default:
break;
}
return 0;
}
}