The eclipse compiler shows Null pointer exception and large number of statements.Actually i am coding for a basic calulator in desktop application and i dont know what went wrong ` import java.awt.*; import java.awt.event.ActionEvent; import java.awt.event.ActionListener;
import javax.swing.*;
class Calcc extends JFrame implements ActionListener
{
Calcc n;
String l="b";
int z=0;
JFrame f;
JTextField t1=new JTextField(30);
JTextField t2=new JTextField(10);
JButton b1=new JButton("1");
JButton b2=new JButton("2");
JButton b3=new JButton("3");
JButton b4=new JButton("4");
JButton b5=new JButton("5");
JButton b6=new JButton("6");
JButton b7=new JButton("7");
JButton b8=new JButton("8");
JButton b9=new JButton("9");
JButton b10=new JButton("0");
JButton b11=new JButton("+");
JButton b12=new JButton("-");
JButton b13=new JButton("*");
JButton b14=new JButton("/");
JButton b15=new JButton("=");
Calcc()
{
f=new JFrame();
f.add(t1);
f.add(t2);
f.add(b1);
f.add(b2);
f.add(b3);
f.add(b4);
f.add(b5);
f.add(b6);
f.add(b7);
f.add(b8);
f.add(b9);
f.add(b10);
f.add(b11);
f.add(b12);
f.add(b13);
f.add(b14);
f.add(b15);
b1.addActionListener(this);
b2.addActionListener(this);
b3.addActionListener(this);
b4.addActionListener(this);
b5.addActionListener(this);
b6.addActionListener(this);
b7.addActionListener(this);
b8.addActionListener(this);
b9.addActionListener(this);
b10.addActionListener(this);
b11.addActionListener(this);
b12.addActionListener(this);
b13.addActionListener(this);
b14.addActionListener(this);
b15.addActionListener(this);
f.setVisible(true);
f.setSize(350,350);
f.setLayout(new FlowLayout());
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public void actionPerformed( ActionEvent e)
{
String d;
d=t1.getText();
if(e.getSource()==b1)
{
t1.setText(d+"1");
}
if(e.getSource()==b2)
{
t1.setText(d+"2");
}
if(e.getSource()==b3)
{
t1.setText(d+"3");
}
if(e.getSource()==b4)
{
t1.setText(d+"4");
}
if(e.getSource()==b5)
{
t1.setText(d+"5");
}
if(e.getSource()==b6)
{
t1.setText(d+"6");
}
if(e.getSource()==b7)
{
t1.setText(d+"7");
}
if(e.getSource()==b8)
{
t1.setText(d+"8");
}
if(e.getSource()==b9)
{
t1.setText(d+"9");
}
if(e.getSource()==b10)
{
t1.setText(d+"0");
}
if(e.getSource()==b11)
{
t1.setText(d+"+");
}
if(e.getSource()==b12)
{
t1.setText(d+"-");
}
if(e.getSource()==b13)
{
t1.setText(d+"*");
}
if(e.getSource()==b14)
{
t1.setText(d+"/");
}
if(e.getSource()==b15)
{
while(l!="a")
{
int b=n.CalcA(d);
if(l=="+")
z=z+b;
else if(l=="-")
z=z-b;
else if(l=="*")
z=z*b;
else if(l=="*")
z=z*b;
}
t2.setText(String.valueOf(z));
}
}
int CalcA(String d1)
{
l="a";
int k = 0;
while((d1!="+")&&(d1!="-")&&(d1!="*")&&(d1!="/"))
{
if(d1!="\n")
break;
k=k*10+Integer.valueOf(d1);
}
l=d1;
return k;
}
}
public class CalcD
{
public static void main(String[] args)
{
new Calcc();
}
}
`
