我这个java计算器为啥只能输入一位数?

我这个java计算器为啥只能输入一位数?
import java.awt.*;import java.awt.event.*;
import javax.swing.*;
public class NewCalculator extends WindowAdapter { JPanel j1 = new JPanel();
JPanel j2 = new JPanel();

JTextField jt = new JTextField(3);
private JButton[] b = new JButton[17];
private String s1[] = {1,2,3,+,4,5,6,-,7,8,9,*,c,0,=,/};
static double a;
static String s,str;

public static void main(String[] args) {
(new NewCalculator()).jframe();

} public void jframe(){
JFrame jf = new JFrame(计算器);
for(int i = 0 ; i < 16 ; i++){
b[i] = new JButton(s1[i]);
b[i].setPreferredSize(new Dimension(41,50));
}
for(int i = 0 ; i < 16 ; i++){
j2.add(b[i]);
}

jt.setEditable(false);
jt.setHorizontalAlignment(JTextField.RIGHT);

for(int i = 0 ; i < 16 ; i++){
b[i].addActionListener(new buttonlistener());
}

jf.addWindowListener(this);
jf.setBackground(Color.red);
j1.setLayout(new BorderLayout());
j1.add(jt,North);
j2.setLayout(new FlowLayout(5,5,5));




jf.add(j1,North);
jf.add(j2,Center);
jf.setSize(195, 280);
jf.setVisible(true);
jf.setLocation(200, 200);
jf.setResizable(false);



}
class buttonlistener implements ActionListener{

public void actionPerformed(ActionEvent e) {
if(e.getActionCommand().equals(=)){
jisuan();
str = String.valueOf(a);
jt.setText(str);
s= ;

}else if(e.getActionCommand().equals(+)){
jisuan();
jt.setText(+);
s = +;

}else if(e.getActionCommand().equals(-)){
jisuan();
jt.setText(-);
s = -;

}else if(e.getActionCommand().equals(*)){
jisuan();
jt.setText(*);
s = *;

}else if(e.getActionCommand().equals(/)){
jisuan();
jt.setText(/);
s = /;

}else if(e.getActionCommand().equals(c)){

jt.setText();

}

else {
str = String.valueOf(e.getActionCommand());
jt.setText(str);
}
}
public void jisuan(){
if (s == +) a+=Double.parseDouble(jt.getText());
else if (s == -) a-=Double.parseDouble(jt.getText());
else if (s == *) a*=Double.parseDouble(jt.getText());
else if (s == /) a/=Double.parseDouble(jt.getText());
else a =Double.parseDouble(jt.getText());
}


}

}

你的程序我帮你改完了,你看看吧,改动的地方见注释.import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class NewCalculator extends WindowAdapter {
JPanel j1 = new JPanel();
JPanel j2 = new JPanel();
JTextField jt = new JTextField(3);
private JButton[] b = new JButton[17];
private String s1[] = {1,2,3,+,4,5,6,-,7,8,9,*,c,0,=,/};
static double a;
static String s=,str=;//这里初始化变量s和str
public static void main(String[] args) {
(new NewCalculator()).jframe();
} public void jframe(){
JFrame jf = new JFrame(计算器);
for(int i = 0 ; i < 16 ; i++){
b[i] = new JButton(s1[i]);
b[i].setPreferredSize(new Dimension(41,50));
}
for(int i = 0 ; i < 16 ; i++){
j2.add(b[i]);
}
jt.setEditable(false);
jt.setHorizontalAlignment(JTextField.RIGHT);
for(int i = 0 ; i < 16 ; i++){
b[i].addActionListener(new buttonlistener());
}
jf.addWindowListener(this);
jf.setBackground(Color.red);
j1.setLayout(new BorderLayout());
j1.add(jt,North);
j2.setLayout(new FlowLayout(5,5,5));
jf.add(j1,North);
jf.add(j2,Center);
jf.setSize(195, 280);
jf.setVisible(true);
jf.setLocation(200, 200);
jf.setResizable(false);
}
class buttonlistener implements ActionListener{
public void actionPerformed(ActionEvent e) {
if(e.getActionCommand().equals(=)){
jisuan();
str = String.valueOf(a);
jt.setText(str);
s= =;//这里改一句 s=;改成s==;
}else if(e.getActionCommand().equals(+)){
str=;//这里加一句
jisuan();
jt.setText(+);
s = +;
}else if(e.getActionCommand().equals(-)){
str=;//这里加一句
jisuan();
jt.setText(-);
s = -;
}else if(e.getActionCommand().equals(*)){
str=;//这里加一句
jisuan();
jt.setText(*);
s = *;
}else if(e.getActionCommand().equals(/)){
str=;//这里加一句
jisuan();
jt.setText(/);
s = /;
}else if(e.getActionCommand().equals(c)){
str=;//这里加一句
jt.setText();
}
else {
if(s.equals(=)){//这里加if判断
str=String.valueOf(e.getActionCommand());//这里加一句
jt.setText(str);//这里加一句
s=;//这里加一句
}else{
str += String.valueOf(e.getActionCommand());//这里改一句str = String.valueOf(e.getActionCommand());改成str += String.valueOf(e.getActionCommand());
jt.setText(str);
}
}
}
public void jisuan(){
if (s.equals(+)) a+=Double.parseDouble(jt.getText()); //这里改一句 if判断s==+改成s.equals(+)
else if (s.equals(-)) a-=Double.parseDouble(jt.getText()); //这里改一句 if判断s==-改成s.equals(-)
else if (s.equals(*)) a*=Double.parseDouble(jt.getText()); //这里改一句 if判断s==*改成s.equals(*)
else if (s.equals(/)) a/=Double.parseDouble(jt.getText()); //这里改一句 if判断s==/改成s.equals(/)
else a =Double.parseDouble(jt.getText());
}
}
}

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