java简单计算器--代码

//中南民大08网工二班mz
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import javax.swing.JOptionPane;

public class Calculator extends Applet implements ActionListener{
Button backButton=new Button("退格");
Button clearButton=new Button("清除");
Panel p1 = new Panel(new FlowLayout());
Panel p2 = new Panel(new GridLayout(2,1));
Panel p3 = new Panel(new GridLayout(4,5,5,5));
TextField t=new TextField("0");
float num1=0;
char ch='#';boolean can=false;
public void init(){
t.setFont(new Font("宋体",Font.BOLD,25));
backButton.setFont(new Font("黑体",Font.BOLD,15));
backButton.setForeground(Color.red);
clearButton.setFont(new Font("黑体",Font.BOLD,15));
clearButton.setForeground(Color.red);
p1.add(backButton);
p1.add(clearButton);
backButton.addActionListener(this);
clearButton.addActionListener(this);
p2.add(t);
p2.add(p1);
p2.setBackground(Color.black);
p3.setBackground(Color.black);
this.setLayout(new BorderLayout());
this.add(p2,"North");
this.add(p3,"Center");
String buttonStr = "789/A456*B123-C0.D+=";
for (int i = 0; i < buttonStr.length(); i++)
this.addButton(p3,buttonStr.substring(i, i + 1));
}
private void addButton(Container c, String s)
{Button b = new Button(s);
if (s.equals("A"))
b.setLabel("sqrt");
else if (s.equals("B"))
b.setLabel("1/x");
else if (s.equals("C"))
b.setLabel("%");
else if (s.equals("D"))
b.setLabel("+/-");
b.setForeground(Color.blue);
b.setFont(new Font("黑体",Font.BOLD,15));
c.add(b);
b.addActionListener(this);
}
public void actionPerformed(ActionEvent e){
String act=e.getActionCommand();
if(e.getSource()==backButton){
if(t.getText().length()>1)t.setText(t.getText().substring(0, t.getText().length()-1));
else t.setText("0");
return;}
if(e.getSource()==clearButton){t.setText("0");ch='#';return;}
if(act.equals("+/-")){
if(t.getText().charAt(0)!='-')t.setText("-"+t.getText());
else t.setText(t.getText().substring(1));return;
}
if(act.equals(".")){t.setText(t.getText()+act);return;}
if(act!="1/x"&&act.charAt(0)>='0'&&act.charAt(0)<='9'){
if(can){t.setText(act);can=false;}
else{try{if(Float.parseFloat(t.getText())==0)
{if(t.getText().equals("0."))t.setText(t.getText()+act);
else t.setText(act);
return;
}
else {t.setText(t.getText()+act);return;}
}catch(NumberFormatException e1){
JOptionPane.showMessageDialog(null, "输入格式错误！", "警告！",
JOptionPane.ERROR_MESSAGE);return;}
}
}

if(act.equals("+")||act.equals("-")||act.equals("*")||act.equals("/")||act.equals("%")){
if(ch!='#'){try{num1=cacu(num1,ch,Float.parseFloat(t.getText()));
t.setText(String.valueOf(num1));ch=act.charAt(0);can=true;return;
}catch(NumberFormatException e1){JOptionPane.showMessageDialog(null, "输入格式错误！", "警告！",
JOptionPane.ERROR_MESSAGE);return;}
}
else{try{num1=Float.parseFloat(t.getText());
ch=act

.charAt(0);can=true;return;
}catch(NumberFormatException e1){JOptionPane.showMessageDialog(null, "输入格式错误！", "警告！",
JOptionPane.ERROR_MESSAGE);return;}
}
}
if(act.equals("sqrt")){try{float num=(float)Math.sqrt(Float.parseFloat(t.getText()));
t.setText(String.valueOf(num));can=true;return;
}catch(NumberFormatException e1){JOptionPane.showMessageDialog(null, "输入格式错误！", "警告！",
JOptionPane.ERROR_MESSAGE);return;}
}
if(act.equals("1/x")){try{float num=1/Float.parseFloat(t.getText());
t.setText(String.valueOf(num));can=true;return;
}catch(NumberFormatException e1){JOptionPane.showMessageDialog(null, "输入格式错误！", "警告！",
JOptionPane.ERROR_MESSAGE);return;}
catch(ArithmeticException e1){JOptionPane.showMessageDialog(null, "除0错误！", "警告！",
JOptionPane.ERROR_MESSAGE);return;}
}
if(act.equals("=")){can=true;
try{if(ch=='#')return;
float num=Float.parseFloat(t.getText());
num1=cacu(num1,ch,num);
t.setText(String.valueOf(num1));
ch='#';return;
}catch(NumberFormatException e1){JOptionPane.showMessageDialog(null, "输入格式错误！", "警告！",
JOptionPane.ERROR_MESSAGE);return;}
}
}
public float cacu(float a,char c,float b){
float sum;
switch(c){
case '+':sum=a+b;break;
case '-':sum=a-b;break;
case '*':sum=a*b;break;
case '/':if(b==0){JOptionPane.showMessageDialog(null, "除0错误！", "警告！",
JOptionPane.ERROR_MESSAGE);return 0;}sum=a/b;break;
case '%':if(b==0){JOptionPane.showMessageDialog(null, "除0错误！", "警告！",
JOptionPane.ERROR_MESSAGE);return 0;}sum=a%b;break;
default:return 0;
}
return sum;
}
}