JAVA : parse int method while using it in JTextField not working - user-interface

Question

I made a simple code to calculate BMI but it shows error in the line with the parseInt method can anyone help (a bit new to java :P)
public BmiF(){
super("BMI Calculator");
setLayout(new FlowLayout());
t1 = new JTextField("enter wieght in kg",10);
final int num1 =Integer.parseInt(t1.getText());
add(t1);
t2 = new JTextField("enter hieght in m",10);
final int num2 =Integer.parseInt(t2.getText());
add(t2);
t3 = new JTextField("",10);
t3.setEditable(false);
add(t3, BorderLayout.SOUTH);
b = new JButton("Claculate BMI");
add(b);
b.addActionListener(
new ActionListener(){
public void actionPerformed(ActionEvent event) {
int k = num1/(num2*num2);
t3.setText(String.format("Your BMI is %d",k));
}
}
);
}
}

Answer 1

You're trying to parse the String "enter weight in kg" as int. See java doc here for what your initialization means.
You need to parse the string in the ActionListener and add a catch exception rule.
I've gotten the bellow code to work. Another problem you have is that you need to declare the int or double in the try block of code without the final qualifier, so that you can change the variable after initialization
frame.setLayout(new FlowLayout());
textArea.setEditable(true);
textArea.setPreferredSize(new Dimension(50, 15));
button = new JButton("ok");
button.addActionListener(new ActionListener() {
#Override
public void actionPerformed(ActionEvent e) {
try {
String string = textArea.getText().trim();
int weight = Integer.parseInt(string);
//do stuff with weight variable
System.out.println(weight);
} catch(Exception e1) {
System.out.println("number exception");
}
}
});
frame.add(textField);
frame.add(textArea);
frame.add(button);
frame.setSize(300, 100);
frame.setVisible(true);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);