CODEWITHSUNDEEP
java
helloumarian
helloumarian

Reputation: 19

Body Mass Index Calculator - error

I am creating a body mass index calculator to practice creating a GUI. However, I cannot figure out why I am getting the error shown below. I'm thinking that I'm trying to display the value of BMI incorrectly. Can someone help please?

Exception in thread "main" java.lang.NullPointerException at Source.(Source.java:21) at Main.main(Main.java:5)

import javax.swing.JFrame; 

public class Main {
public static void main (String args []) {
    Source sourceObject = new Source();
    sourceObject.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    sourceObject.setSize(275,180); 
    sourceObject.setVisible(true); 

}

}

import java.awt.FlowLayout; 
import javax.swing.JFrame; 
import javax.swing.JLabel; 
import javax.swing.JOptionPane;

public class Source extends JFrame { 

private JLabel item1;
private JLabel item2;
private JLabel item3;
private String weight, height;
private int BMI;

public Source () {
    super("Title"); 
    setLayout(new FlowLayout()); 
    item1 = new JLabel("Text"); 
    item1.setToolTipText("This appears on hover"); 
    weight = JOptionPane.showInputDialog(null, "Weight: ");
    height = JOptionPane.showInputDialog(null, "Height: ");
    item3.setText(String.valueOf(BMI));
    add(item1);
    add(item2);
    add(item3);

}
int BMICalc() {
    int weig = Integer.parseInt(weight);
    int heig = Integer.parseInt(height);
    int BMI = (weig)/(heig * heig);
    return BMI;

}


}

Upvotes: 0

Views: 241

Answers (2)

Andreas Dolk
Andreas Dolk

Reputation: 114807

You missed to create the JLabels 2 and 3. Try this:

public Source () {
    super("Title"); 
    setLayout(new FlowLayout()); 
    item1 = new JLabel("Text"); 
    item1.setToolTipText("This appears on hover"); 

    item2 = new JLabel("Text");

    weight = JOptionPane.showInputDialog(null, "Weight: ");
    height = JOptionPane.showInputDialog(null, "Height: ");
    BMICalc();        

    item3 = new JLabel("Text");
    item3.setText(String.valueOf(BMI));
    add(item1);
    add(item2);
    add(item3);
}

Upvotes: 0

davidxxx
davidxxx

Reputation: 131456

Actually item2 and item3 are declared but never instantiated.

But the actual problem is you are calling a method on item3.

Instantiate all the fields that have a known value in the Source constructor.

Upvotes: 1

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