Method Calling (Static/Non-Static)

Question

I'm kind of new to Java and I'm struggling with calling a method from another class.

Class 1

public void SetColourCheck()
    {
        this.Tick = ColourCheck;
    }

    public JLabel GetColourCheck()
    {
        return this.Tick;
    }

Class 2

public void TickCheck()
    {
        JLabel Tick = GUI.GetColourCheck();

        ColourState();
        Tick.setEnabled(true);
    }

On Class 2, I'm getting the error non-static method GetColourCheck() cannot be referenced from a static context on JLabel Tick.

Edited: Is this what you mean when you say Constructor code?

public class GUI extends javax.swing.JFrame {

    GUI TestGUI;
    public JLabel Tick;

    public GUI(GUI aThis) {
        initComponents();
        TestGUI = aThis;
    }

All this appears in the console.

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at Scoring.ColourPicker.ColourState(ColourPicker.java:345)
    at Scoring.ColourPicker.BlueSliderStateChanged(ColourPicker.java:326)
    at Scoring.ColourPicker.access$500(ColourPicker.java:13)
    at Scoring.ColourPicker$6.stateChanged(ColourPicker.java:197)
    at java.desktop/javax.swing.JSlider.fireStateChanged(JSlider.java:439)
    at java.desktop/javax.swing.JSlider$ModelListener.stateChanged(JSlider.java:354)
    at java.desktop/javax.swing.DefaultBoundedRangeModel.fireStateChanged(DefaultBoundedRangeModel.java:371)
    at java.desktop/javax.swing.DefaultBoundedRangeModel.setRangeProperties(DefaultBoundedRangeModel.java:309)
    at java.desktop/javax.swing.DefaultBoundedRangeModel.setValueIsAdjusting(DefaultBoundedRangeModel.java:238)
    at java.desktop/javax.swing.JSlider.setValueIsAdjusting(JSlider.java:652)
    at java.desktop/javax.swing.plaf.basic.BasicSliderUI$TrackListener.mouseDragged(BasicSliderUI.java:2081)
    at java.desktop/java.awt.Component.processMouseMotionEvent(Component.java:6680)
    at java.desktop/javax.swing.JComponent.processMouseMotionEvent(JComponent.java:3360)
    at java.desktop/java.awt.Component.processEvent(Component.java:6401)
    at java.desktop/java.awt.Container.processEvent(Container.java:2263)
    at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5008)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4840)
    at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4918)
    at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4564)
    at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4488)
    at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307)
    at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2772)
    at java.desktop/java.awt.Component.dispatchEvent(Component.java:4840)
    at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
    at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)

Does this answer your question? [What is the reason behind "non-static method cannot be referenced from a static context"?](https://stackoverflow.com/questions/290884/what-is-the-reason-behind-non-static-method-cannot-be-referenced-from-a-static) — QBrute, Feb 28 '20 at 09:35

score 0 · Accepted Answer · answered Feb 28 '20 at 09:38

0

public void SetColourCheck() is an instance method, which can be called using an object alone. Assuming the class name is GUI , the call you did GUI.GetColourCheck() is not using the object of GUI.

So it must be like new GUI().SetColourCheck() or use the object if you have created one.

answered Feb 28 '20 at 09:38

Kris

8,680
4
39
67

Thank you, makes sense now. – Nat Feb 28 '20 at 09:43
It works but doesn't, I'm now getting this error in the console, followed by loads more text. `Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException` – Nat Feb 28 '20 at 09:53
From these lines of code you posted, its hard to say what caused the NPE – Kris Feb 28 '20 at 10:22
I have only received that error from `new GUI().SetColourCheck()`. If that helps? I would make this a separate question itself but It will not allow me to. – Nat Feb 28 '20 at 10:25
Post the entire stack trace and constructor code of GUI – Kris Feb 28 '20 at 10:26
I'll edit the main question – Nat Feb 28 '20 at 10:50

Method Calling (Static/Non-Static)

1 Answers1