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java退格键运行代码 java里面如何退格
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java编写计算器实现退格，倒数，小数点，正负号功能代码
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
class General extends JFrame implements ActionListener
{
String args[]={"退格","总清","清零","/","1","2","3","+","4","5","6","-","7","8","9","*","0","+/-",".","="};
JButton jb[]=new JButton[20];
JPanel p1=new JPanel();
JTextField jtf=new JTextField(15);
double num1,num2,jieguo;
char c,ch;
public General()
{
Container ct=getContentPane();
jtf.addKeyListener(new KA());
jtf.setHorizontalAlignment(JTextField.RIGHT);
ct.add(jtf,"North");
p1.setLayout(new GridLayout(5,4));
for(int i=0;i20;i++)
{
jb[i]=new JButton(args[i]);
jb[i].addActionListener(this);
p1.add(jb[i]);
}
ct.add(p1);
pack();
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public static void main(String args[])
{
new General();
}
public void actionPerformed(ActionEvent e)// 监听按键
{
String str=e.getActionCommand().trim();
if("0123456789.".indexOf(str)!=-1)
{
if(jtf.getText().equals("0"))jtf.setText(null);
jtf.setText(jtf.getText()+str);
return;
}
if("+-*/".indexOf(str)!=-1)
{
num1=Double.parseDouble(jtf.getText());
c=str.charAt(0);
jtf.setText(null);
return;
}
else if(str.equals("="))
{
num2=Double.parseDouble(jtf.getText());
switch(c)
{
case '+': jieguo=num1+num2; break;
case '-': jieguo=num1-num2; break;
case '*': jieguo=num1*num2; break;
case '/': jieguo=num1/num2; break;
}
jtf.setText(Double.toString(jieguo));
}
else if(str.equals("+/-"))
{
if(jtf.getText().isEmpty()==false)
{
Double lnum=-(Double.parseDouble(jtf.getText()));
jtf.setText(Double.toString(lnum));
}
else
{
jtf.setText("-");
}
}
else if(str.equals("清空"))
{
jtf.setText(null);
}
else if(str.equals("清零"))
{
jtf.setText("0");
}
else if(str.equals("退格"))
{
jtf.setText(jtf.getText().substring(0,jtf.getText().length()-1));
}
}
class KA extends KeyAdapter // 监听键盘
{
public void keyPressed(KeyEvent e)
{
char ch=e.getKeyChar();
if("+-*/".indexOf(ch)!=-1)
{
num1=Double.parseDouble(jtf.getText());
c=ch;
}
if(ch=='='|ch==e.VK_ENTER)
{
num2=Double.parseDouble(jtf.getText());
switch(c)
{
case '+': jieguo=num1+num2; break;
case '-': jieguo=num1-num2; break;
case '*': jieguo=num1*num2; break;
case '/': jieguo=num1/num2; break;
}
}
}
public void keyReleased(KeyEvent e)
{
char ch=e.getKeyChar();
if("+-*/".indexOf(ch)!=-1)
{
jtf.setText(null);
}
if(ch=='='|e.getKeyCode()==e.VK_ENTER)
{
jtf.setText(Double.toString(jieguo));
}
}
}
}
相关问答
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package lee;
/*文件名：Calculator.java
*说明：简易科学计算器
*/
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Calculator extends Frame implements ActionListener, WindowListener
{
private Container container;
private GridBagLayout layout;
private GridBagConstraints constraints;
private JTextField displayField; //计算结果显示区
private String lastCommand; //保存+,-,*,/,=命令0
private double result; //保存计算结果
private boolean start; //判断是否为数字的开始
private JMenuBar menubar;
private JMenuItem m_exit,m2_ejz,m2_bjz;
private Dialog dialog;
private Label label_dialog;
private JButton button_sqrt,button_plusminus,button_CE,button_cancel,button_1,button_2,
button_3,button_4,button_5,button_6,button_7,button_8,button_9,button_0,
button_plus,button_minus,button_multiply,button_divide,button_point,
button_equal,button_log,button_tan,button_cos,button_sin,button_exp;
public Calculator() //构造方法设置布局、为按钮注册事件监听器
{
super("Calculator");
this.setLocation(240,200);
this.setSize(350,300);
this.setResizable(true);
this.setLayout(new GridLayout(7,1));
this.addmyMenu(); //调用成员方法添加菜单
displayField=new JTextField(30);
this.add(displayField);
displayField.setEditable(true);
start=true;
result=0;
lastCommand = "=";
JPanel panel0=new JPanel();
panel0.setLayout(new GridLayout(1,4,4,4));
JPanel panel1=new JPanel();
panel1.setLayout(new GridLayout(1,5,4,4));
this.add(panel1);
button_sqrt=new JButton("sqrt");
button_plusminus=new JButton("+/-");
button_exp=new JButton("exp");
button_CE=new JButton("退格");
button_cancel=new JButton("C");
JPanel panel2=new JPanel();
panel2.setLayout(new GridLayout(1,5,4,4));
this.add(panel2);
button_7=new JButton("7");
button_8=new JButton("8");
button_9=new JButton("9");
button_log=new JButton("log");
button_divide=new JButton("/");
JPanel panel3=new JPanel();
panel3.setLayout(new GridLayout(1,5,4,4));
this.add(panel3);
button_4=new JButton("4");
button_5=new JButton("5");
button_6=new JButton("6");
button_tan=new JButton("tan");
button_multiply=new JButton("*");
JPanel panel4=new JPanel();
panel4.setLayout(new GridLayout(1,5,4,4));
this.add(panel4);
button_1=new JButton("1");
button_2=new JButton("2");
button_3=new JButton("3");
button_cos=new JButton("cos");
button_minus=new JButton("-");
JPanel panel5=new JPanel();
panel5.setLayout(new GridLayout(1,5,4,4));
this.add(panel5);
button_0=new JButton("0");
button_point=new JButton(".");
button_equal=new JButton("=");
button_sin=new JButton("sin");
button_plus=new JButton("+");
panel1.add(button_sqrt);
panel1.add(button_plusminus);
panel1.add(button_exp);
panel1.add(button_CE);
panel1.add(button_cancel);
panel2.add(button_7);
panel2.add(button_8);
panel2.add(button_9);
panel2.add(button_log);
panel2.add(button_divide);
panel3.add(button_4);
panel3.add(button_5);
panel3.add(button_6);
panel3.add(button_tan);
panel3.add(button_multiply);
panel4.add(button_1);
panel4.add(button_2);
panel4.add(button_3);
panel4.add(button_cos);
panel4.add(button_minus);
panel5.add(button_0);
panel5.add(button_point);
panel5.add(button_equal);
panel5.add(button_sin);
panel5.add(button_plus);
button_sqrt.addActionListener(this);
button_plusminus.addActionListener(this);
button_exp.addActionListener(this);
button_CE.addActionListener(this);
button_cancel.addActionListener(this);
button_7.addActionListener(this);
button_8.addActionListener(this);
button_9.addActionListener(this);
button_log.addActionListener(this);
button_divide.addActionListener(this);
button_4.addActionListener(this);
button_5.addActionListener(this);
button_6.addActionListener(this);
button_tan.addActionListener(this);
button_multiply.addActionListener(this);
button_1.addActionListener(this);
button_2.addActionListener(this);
button_3.addActionListener(this);
button_cos.addActionListener(this);
button_minus.addActionListener(this);
button_0.addActionListener(this);
button_point.addActionListener(this);
button_equal.addActionListener(this);
button_sin.addActionListener(this);
button_plus.addActionListener(this);
this.addWindowListener(new WinClose()); //注册窗口监听器
this.setVisible(true);
}
private void addmyMenu() //菜单的添加
{
JMenuBar menubar=new JMenuBar();
this.add(menubar);
JMenu m1=new JMenu("选项");
JMenu m2=new JMenu("进制转换");
JMenuItem m1_exit=new JMenuItem("退出");
m1_exit.addActionListener(this);
JMenuItem m2_ejz=new JMenuItem("二进制");
m2_ejz.addActionListener(this);
JMenuItem m2_bjz=new JMenuItem("八进制");
m2_bjz.addActionListener(this);
JMenu m3 = new JMenu(" 帮助");
JMenuItem m3_Help = new JMenuItem("用法");
m3_Help.addActionListener(this);
dialog = new Dialog(this,"提示",true); //模式窗口
dialog.setSize(240,80);
label_dialog = new Label("",Label.CENTER); //标签的字符串为空，居中对齐
dialog.add(label_dialog);
dialog.addWindowListener(this); //为对话框注册窗口事件监听器
m1.add(m1_exit);
menubar.add(m1);
m2.add(m2_ejz);
m2.add(m2_bjz);
menubar.add(m2);
m3.add(m3_Help);
menubar.add(m3); }
public void actionPerformed(ActionEvent e) //按钮的单击事件处理方法
{
if(e.getSource().equals(button_1)||e.getSource().equals(button_2)||
e.getSource().equals(button_3)||e.getSource().equals(button_4)||
e.getSource().equals(button_5)|| e.getSource().equals(button_6)||
e.getSource().equals(button_7)|| e.getSource().equals(button_8)||
e.getSource().equals(button_9) ||e.getSource().equals(button_0)||
e.getSource().equals(button_point)||e.getSource().equals(button_plusminus)||
e.getSource().equals(button_cancel)||e.getSource().equals(button_CE))
{ //非运算符的处理方法
String input=e.getActionCommand();
if (start)
{
displayField.setText("");
start=false;
if(input.equals("+/-"))
displayField.setText(displayField.getText()+"-");
}
if(!input.equals("+/-"))
{
String str=displayField.getText();
if(input.equals("退格")) //退格键的实现方法
{
if(str.length()0)
displayField.setText(str.substring(0,str.length()-1));
}
else if(input.equals("C")) //清零键的实现方法
{
displayField.setText("0");
start=true;
}
else
displayField.setText(displayField.getText()+input);
}
}
else if (e.getActionCommand()=="二进制") //二进制的转换
{
int n=Integer.parseInt(displayField.getText());
displayField.setText(Integer.toBinaryString(n));
}
else if (e.getActionCommand()=="八进制") //八进制的转换
{
int n=Integer.parseInt(displayField.getText());
displayField.setText(Integer.toOctalString(n));
}
else if (e.getActionCommand()=="退出") //选项中退出的处理方法
{
System.exit(0);
}
else if (e.getActionCommand()=="用法") //按下'帮助'菜单栏中用法的处理方法
{
label_dialog.setText("sqrt,exp等键是先输运算符再输数字\n");
dialog.setLocation(400,250);
dialog.setVisible(true);
}
else //各运算符的识别
{
String command=e.getActionCommand();
if(start)
{
lastCommand=command;
}
else
{
calculate(Double.parseDouble(displayField.getText()));
lastCommand=command;
start=true;
}
}
}
public void calculate(double x) //各运算符的具体运算方法
{
double d=0;
if (lastCommand.equals("+"))
result+= x;
else if (lastCommand.equals("-"))
result-=x;
else if (lastCommand.equals("*"))
result*=x;
else if (lastCommand.equals("/"))
result/=x;
else if (lastCommand.equals("="))
result=x;
else if (lastCommand.equals("sqrt"))
{
d=Math.sqrt(x);
result=d;
}
else if (lastCommand.equals("exp"))
{
d=Math.exp(x);
result=d;
}
else if (lastCommand.equals("log"))
{
d=Math.log(x);
result=d;
}
else if (lastCommand.equals("tan"))
{
d=Math.tan(x);
result=d;
}
else if (lastCommand.equals("cos"))
{
d=Math.cos(x);
result=d;
}
else if (lastCommand.equals("sin"))
{
d=Math.sin(x);
result=d;
}
displayField.setText(""+ result);
}
public void windowClosing(WindowEvent e)
{
if(e.getSource()==dialog)
dialog.setVisible(false); //隐藏对话框
else
System.exit(0);
}
public void windowOpened(WindowEvent e) { }
public void windowActivated(WindowEvent e) { }
public void windowDeactivated(WindowEvent e) { }
public void windowClosed(WindowEvent e) { }
public void windowIconified(WindowEvent e) { }
public void windowDeiconified(WindowEvent e) { }
public static void main(String args[])
{
Calculator calculator=new Calculator();
}
}
class WinClose implements WindowListener
{
public void windowClosing(WindowEvent e) //单击窗口关闭按钮时触发并执行实现窗口监听器接口中的方法
{
System.exit(0); //结束程序运行
}
public void windowOpened(WindowEvent e){}
public void windowActivated(WindowEvent e){}
public void windowDeactivated(WindowEvent e){}
public void windowClosed(WindowEvent e){}
public void windowIconified(WindowEvent e){}
public void windowDeiconified(WindowEvent e){}
}
Q2: JAVA 中 按回车键退出的 程序代码怎么写？
import java.io.IOException;
public class TestEnter {
public static void main(String[] args) throws IOException{
while(true){
if(System.in.read() == '\n')
System.exit(0);
}
}
}
Q3: Java实现“按任意键退出”
System.out.println("***********************************");
System.out.println("\n请输入java退格键运行代码你要选择java退格键运行代码的操作:\n 1:进入..\n 2:进入...:\n其它任一键java退格键运行代码：退出\n");
System.out.println("***********************************");
try
{
BufferedReader in=new BufferedReader(new InputStreamReader(System.in));
String str=in.readLine();
int chioce=Integer.parseInt(str);
switch(chioce)
{
case 1: break;
case 2: break;
default: System.exit(0);
}
}
catch(NumberFormatException e){System.exit(0);}
catch(IOException ie){System.exit(0);}
Q4: java 退格键的控制字符是什么？
是的啊，退格就是\b。你可以用e.KeyCode==8试试。bs(backspace)
我这里有一个ascii码，你以后可以对照看
Q5: java 写计算器的退格键怎么写，如“123456”按下退格变“12345”
String str = "12345";
str = str.substring(0, str.length()-1);
int a = Integer.parseInt(str);
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