Why showing Null Pointer Exception While using JFrame in Eclipse?

Question

Error******************************************************************

Exception in thread "main" java.lang.NullPointerException
at java.awt.Window.init(Unknown Source)
at java.awt.Window.<init>(Unknown Source)
at java.awt.Frame.<init>(Unknown Source)
at java.awt.Frame.<init>(Unknown Source)
at javax.swing.JFrame.<init>(Unknown Source)
at Main.main(Main.java:12)

Code********************************************************************

import javax.swing.JFrame;
import javax.swing.JSlider;

import com.fazecast.jSerialComm.*;

public class Main {

    /**
     * @param args
     */
    public static void main(String[] args) {
        JFrame w = new JFrame();
        JSlider slider = new JSlider();
        slider.setMinimum(1023);
        w.add(slider);
        w.pack();
        w.setVisible(true);     
    }
}

Are you sure that's the exact code you're running? Works fine on my machine. — Jonathan Sterling, Mar 30 '17 at 10:01
The answers in that other question are very helpful in case of a `NullPointerException` in one’s own code. This exception comes from deep within AWT behind a call to a Swing constructor, so it’s different. @Japu_D_Cret — Ole V.V., Mar 30 '17 at 10:21
what is your Runtime Environment? exact Java Version and Manufacturer? (e.g. OpenJDK 1.8.0_121) — Japu_D_Cret, Mar 30 '17 at 10:23
I downloaded and installed New JDK. Does eclipse can access this ? — Sarath V R, Mar 30 '17 at 10:56

score 1 · Answer 1 · answered Mar 31 '17 at 02:10

1

Thank you Jonathan Sterling, Japu_D_Cret and chetan mehra. It worked well. I downloaded the exact version of Eclipse (Luna) prescribed in that video [ youtu.be/8B6j_yr9H8g ] and new JDK, Nothing else. The problem was with the IDE.

answered Mar 31 '17 at 02:10

Sarath V R

23
4

score 0 · Answer 2 · answered Mar 30 '17 at 10:04

0

you hadnt add setbounds(); in your java code try w.setbounds(100,100,200,200);.Usually null pointer exception came when the reference of an object is null.Try this .Hope it will work for you.

answered Mar 30 '17 at 10:04

chetan mehra

11

What is setbounds(); – Sarath V R Mar 30 '17 at 10:26
How can I add setbounds(); to my program ? – Sarath V R Mar 30 '17 at 10:27
1

it's a method of `java.awt.Component` from which your JFrame and your JSlider inherit - you can call it on your JFrame with `w.setBounds(int, int, int, int)` but this will most certainly not fix your problem since your error occurs in the initialization of the JFrame in the first line, see http://docs.oracle.com/javase/7/docs/api/java/awt/Component.html for reference – Japu_D_Cret Mar 30 '17 at 10:29
Actually I found this code form YouTube , https://youtu.be/8B6j_yr9H8g , And not working on My computer – Sarath V R Mar 30 '17 at 10:35
which ide are you using? – chetan mehra Mar 30 '17 at 10:52
Since you are using a public class so name of the class and name of program must be same with.java extension.I run this code and it works fine in my machine – chetan mehra Mar 30 '17 at 11:03
I cannot believe this answer answers the question. I see no connection to the stacktrace reported. Also `w.pack()` should set a suitable window size. – Ole V.V. Mar 30 '17 at 11:26
IDE I am using : eclipse for android development. – Sarath V R Mar 30 '17 at 14:02

Why showing Null Pointer Exception While using JFrame in Eclipse?

2 Answers2