Calculator using JOptionPane

Question

plz tell me what is the error in this code.
my code did not work correctly.
import javax.swing.JOptionPane;
class cal
public static void main(String args[])
String a=null;
String b=null;
String c=null;
JOptionPane.showMessageDialog(null,"Menu","INPUT",JOptionPane.PLAIN_MESSAGE);
JOptionPane.showMessageDialog(null,"Menu","press+ for addition",JOptionPane.PLAIN_MESSAGE);
JOptionPane.showMessageDialog(null,"Menu","press - for subtraction ",JOptionPane.PLAIN_MESSAGE);
JOptionPane.showMessageDialog(null,"Menu","press * for multiplication",JOptionPane.PLAIN_MESSAGE);
JOptionPane.showMessageDialog(null,"Menu","press / for divide",JOptionPane.PLAIN_MESSAGE);
JOptionPane.showInputDialog("enter first value");
JOptionPane.showInputDialog("enter second value");
JOptionPane.showInputDialog("enter operator ");
int i=Integer.parseInt(a);
int j=Integer.parseInt(b);
int k=Integer.parseInt(c);
switch (k)
case'+':
JOptionPane.showMessageDialog(null,"the addition of two number is"+(i+j),"result",JOptionPane.PLAIN_MESSAGE);
break;
case'-':
JOptionPane.showMessageDialog(null,"the subtraction of two number is"+(i-j),"result",JOptionPane.PLAIN_MESSAGE);
break;
case'*':
JOptionPane.showMessageDialog(null,"the multiplication of two number is"+(i*j),"result",JOptionPane.PLAIN_MESSAGE);
break;
case'/':
JOptionPane.showMessageDialog(null,"the division of two number is"+(i/j),"result",JOptionPane.PLAIN_MESSAGE);
default:
JOptionPane.showMessageDialog(null,"ur operator is wrong","INPUT",JOptionPane.PLAIN_MESSAGE);
}

Answer 1

I'll tell you one thing more, then I'm off. Replace:
int i=Integer.parseInt(a);
int j=Integer.parseInt(b);
int k=Integer.parseInt(c);... With:
int i=Integer.parseInt(JOptionPane.showInputDialog("enter first value"));
int j=Integer.parseInt(JOptionPane.showInputDialog("enter second value"));
char[] chars = JOptionPane.showInputDialog("enter operator ").toCharArray();
char k=chars[0];~Bill