【实例简介】

【实例截图】

【核心代码】

import javax.swing.*;

import java.awt.*;

import java.util.HashMap;

import java.util.Stack;

/**

* Created by 28713 on 2016/9/11.

*/

public class Calculator extends JFrame{

private Stack operandStack= new Stack<>();

private Stack operatorStack = new Stack<>();

private Calculator(){

setTitle("计算器");

setSize(266,340);

Container c=getContentPane();

c.setLayout(null);

JTextArea jt=new JTextArea(100,100);

jt.setFont(new Font("Aria",Font.BOLD,32));

jt.setLineWrap(true);

JScrollPane sp=new JScrollPane(jt);

jt.setCaretPosition(jt.getDocument().getLength());

sp.setBounds(0,0,250,100);

c.add(sp);

JPanel p=new JPanel();

p.setLayout(new GridLayout(5,4,0,0));

p.setBounds(0,100,250,200);

String[] num={"(",")","AC","/","7","8","9","*","4","5","6","-","1","2","3"," ","0",".","DEL","="};

JButton[] jb=new JButton[20];

for(int i=0;i<20;i ){

jb[i]=new JButton(num[i]);

p.add(jb[i]);

}

c.add(p);

for(int i=0;i<18;i ){

if(i!=2){

final int j=i;

jb[i].addActionListener(e-> jt.append(num[j]));

}

}

jb[2].addActionListener(e->{

jt.setText("");

operandStack.clear();

operatorStack.clear();

});

jb[18].addActionListener(e->{

try{

jt.setText(jt.getText().substring(0,jt.getText().length()-1));

}catch(Exception ignored) { }//忽略这个异常 IDEA就是好用！！！

});

jb[19].addActionListener(e->{

try{

double x= calculate(jt.getText() "#");

jt.setText("");

jt.append(String.valueOf(x));

}catch(Exception ex){

if(ex.getMessage()==null)

jt.setText("ERROR!");

else

jt.setText(ex.getMessage());

}

});

//禁止文本域的enter换行

KeyStroke enter = KeyStroke.getKeyStroke("ENTER");

jt.getInputMap().put(enter, "none");

this.getRootPane().setDefaultButton(jb[19]);

//太累！不想研究了

//下面的，不知道主体是什么，当只有焦点在那个主体上才会响应，哎，不知道怎么弄。

/*c.addKeyListener(new KeyAdapter() {

@Override

public void keyPressed(KeyEvent e) {

if(e.getKeyCode()==KeyEvent.VK_ENTER){

System.out.println("adssdf");

double x= calculate(jt.getText() "#");

jt.setText("");

jt.append(String.valueOf(x));

}

}

});*/

//不知道为什么响应不了键盘事件？？？

//不知道为什么下面的的这个不行？？？

setVisible(true);

setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

}

private void calculate(){

String b = operatorStack.pop();

double c = operandStack.pop();

double d = operandStack.pop();

double e;

if (b.equals(" ")) {

e = d c;

operandStack.push(e);

}

if (b.equals("-")) {

e = d - c;

operandStack.push(e);

}

if (b.equals("*")) {

e = d * c;

operandStack.push(e);

}

if (b.equals("/")) {

if(c==0)

throw new ArithmeticException("DivideByZero!");//不可修改为Exception

// Exception的异常是必须处理的,是受控异常;而ArithmeticException 不是必须处理的 ,受控异常必须强制处理

e = d / c;

operandStack.push(e);

}

}

private Double calculate(String text){

HashMap precede=new HashMap<>();

precede.put("(",0);

precede.put(")",0);

precede.put("/",2);

precede.put("*",2);

precede.put("-",1);

precede.put(" ",1);

precede.put("#",0);

operatorStack.push("#");

int flag=0;

for(int i=0;i

String a=String.valueOf(text.charAt(i));

if(!a.matches("[0-9.]")){

if(flag!=i)

operandStack.push(Double.parseDouble(text.substring(flag,i)));

flag=i 1;

while(!(a.equals("#")&&operatorStack.peek().equals("#"))){

if(precede.get(a)>precede.get(operatorStack.peek())||a.equals("(")){

operatorStack.push(a);

break;

}else {

if(a.equals(")")) {

while(!operatorStack.peek().equals("("))

calculate();

operatorStack.pop();

break;

}

calculate();

}

}

}

}

return(operandStack.pop());

}

public static void main(String[] args){

new Calculator();

}

}