Tlauncher произошла ошибка exception in thread awt eventqueue 0 java lang

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24.04.2014, 18:11. Показов 8496. Ответов 4

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import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Statement;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
 
import com.mysql.jdbc.PreparedStatement;
import com.mysql.jdbc.ResultSetMetaData;
 
 
public class MainDebt {
    
    private static Connection conn;
    String debtor, sum;
    int counter;
    
    
    
    public  void note() throws SQLException{
        getStrings();
            String update = "INSERT INTO Debts (id, debtor,sum) values (?,?,?)";
            PreparedStatement prst = (PreparedStatement) conn.prepareStatement(update);
            prst.setInt (1, counter );
                prst.setString (2, debtor);
                prst.setString   (3, sum);
                prst.execute();
        
    }   
     
    
    
    void getStrings(){
        
        debtor = DebtWin.getDebtor().getText();
        sum = DebtWin.getSum().getText();
        System.out.println(debtor);
        System.out.println(sum);
        counter++;
        
    }
    
    void showTable() throws SQLException{
        
        Statement st = conn.createStatement();
        ResultSet rs = st.executeQuery("select * from Debts;");
        
        while (rs.next()) {
            System.out.println(rs.getInt(1) + " " + rs.getString(2)+ " "+ rs.getString(2) );
        }
        
        System.out.println();
    }
    
    
     static void  connect() throws SQLException{
        
        String url = "jdbc:mysql://localhost/bookstore" +
                "?autoReconnect=true&useUnicode=true&characterEncoding=utf8";
        String name = "root";
        String password = "5757254";
            Connection conn = DriverManager.getConnection(url, name, password);
            System.out.println("Connected.");
            Statement st = conn.createStatement();
             String createTable = "create table IF NOT EXISTS Debts (id INT, debtor VARCHAR(10), sum VARCHAR(10));";
             String cleanTable = "DELETE FROM Debts;";
             st.execute (cleanTable);
             Statement st2 = conn.createStatement();
                st2.execute(createTable);
                System.out.println("clean");
                
    }
 
}

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import java.awt.EventQueue;
 
 
public class DebtWin {
 
    private JFrame frame;
    private static JTextField debtor;
    private static JTextField sum;
    
    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    DebtWin window = new DebtWin();
                    window.frame.setVisible(true);
                    MainDebt.connect();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }
 
    /**
     * Create the application.
     */
    public DebtWin() {
        initialize();
    }
 
    /**
     * Initialize the contents of the frame.
     */
    private void initialize() {
        frame = new JFrame();
        frame.setBounds(100, 100, 450, 300);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.getContentPane().setLayout(null);
        
        debtor = new JTextField();
        debtor.setBounds(115, 30, 114, 20);
        frame.getContentPane().add(debtor);
        debtor.setColumns(10);
        
        sum = new JTextField();
        sum.setBounds(115, 71, 114, 20);
        frame.getContentPane().add(sum);
        sum.setColumns(10);
        
        JLabel label = new JLabel("Должник :");
        label.setBounds(10, 33, 86, 14);
        frame.getContentPane().add(label);
        
        JLabel lblNewLabel = new JLabel("Сумма :");
        lblNewLabel.setBounds(26, 74, 46, 14);
        frame.getContentPane().add(lblNewLabel);
        
        JButton btnNewButton = new JButton("Записать");
        btnNewButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent arg0) {
                try {
                        MainDebt md = new MainDebt();
                        md.note();
                    } catch (SQLException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                
                
            }
        });
        btnNewButton.setBounds(118, 124, 111, 35);
        frame.getContentPane().add(btnNewButton);
    }
    
    
    
    static JTextField getDebtor(){
        return debtor;
    }
     
    static JTextField getSum(){
        return sum;
    }
    
}

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GET: version.md5

Java Path: C:/Program Files (x86)/MinecraftLauncher1/jreAMD64/bin/java.exe
Heap size: 679.0

System Arch: amd64

16 achievements

Head acc: + 87
Body acc: + 8
CONFLICT @ -134

452 recipes

lang: ru_RU

water_mode: 0
anti_aliasing: 2
reflection_resolution: 4
reflective_items: true
reflective_clouds: false
reflect_player: true
render_v3: 1.0
water_surface_transparency: 0.05
waterfall_transparency: 0.4
water_color: 0.0, 0.4, 0.3
waterfall_color: 1.0, 1.0, 1.0
waterfall_fog: true

WARNING: Found unknown Windows version: Windows 7
Attempting to use default windows plug-in.
Loading: net.java.games.input.DirectAndRawInputEnvironmentPlugin

Starting up SoundSystem…

Initializing LWJGL OpenAL
(The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
OpenAL initialized.

Card name: NVIDIA Corporation

Connecting to n1.mcgl.ru, 1138
Remove /gui/planets/13.png
Remove /gui/planets/14.png
Remove /gui/systems/1024×512/0-on.png
Remove /gui/systems/1024×512/0-off.png
Remove /gui/systems/1024×512/1-on.png
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Remove /gui/systems/1024×512/2-on.png
Remove /gui/systems/1024×512/2-off.png
Remove /gui/systems/1024×512/3-on.png
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Remove /gui/systems/1024×512/4-on.png
Remove /gui/systems/1024×512/4-off.png
Remove /gui/systems/1024×512/bg.png
IP: 86.62.89.4

Server proto: 2

LOGIN: user = rostislav.bat, uid = 295684, proto = 2
Hogwarts
pos: -2,30,-46
Loc: 0 : 1377720000000
Add paint: http://forum.mcgl.ru/images/shyvakin/strelka, tm: 0
pos: -5,28,-20
Loc: 1381480628960 : 1380139200000
Add paint: http://forum.mcgl.ru/images/-_LeOn_-/gonki, tm: 0
pos: 1,30,-46
pos: 0,32,-25
pos: 6,28,-20
pos: 1,29,-25
Spawn PLAYER: CraftMan18RUS
Spawn PLAYER: DUMBASS77
Spawn PLAYER: vlad2003vlad
New max size: 324
New max size: 484
New max size: 784

Load URL: http://forum.mcgl.ru/getdata/295684/skin

Load region: map_57_-256_-256.png
Load URL: http://forum.mcgl.ru/getdata/295684/cloak
Load region: map_57_-256_0.png
Load region: map_57_0_-256.png
Load region: map_57_0_0.png

Load URL: clans/_npc

Load URL: http://forum.mcgl.ru/getdata/110344/skin

Load URL: http://forum.mcgl.ru/getdata/110344/cloak

Load URL: http://forum.mcgl.ru/getdata/391442/skin

Load URL: http://forum.mcgl.ru/getdata/391442/cloak

Load URL: http://forum.mcgl.ru/getdata/378035/skin

Load URL: http://forum.mcgl.ru/getdata/378035/cloak

java.lang.NullPointerException
at net.minecraft.I.em.B(Unknown Source)
at net.minecraft.I.em.A(Unknown Source)
at net.minecraft.N.e.C(Unknown Source)
at net.minecraft.N.cb.G(Unknown Source)
at net.minecraft.U.mo.A(Unknown Source)
at net.minecraft.G.ky.A(Unknown Source)
at net.minecraft.U.ro.A(Unknown Source)
at net.minecraft.U.mo.B(Unknown Source)
at net.minecraft.N.cb.?(Unknown Source)
at net.minecraft.client.Minecraft.S(Unknown Source)
at net.minecraft.client.Minecraft.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
java.lang.NullPointerException
at net.minecraft.L.D.A(Unknown Source)
at net.minecraft.L.H.I(Unknown Source)
at net.minecraft.L.A.run(Unknown Source)

java.lang.NullPointerException
at net.minecraft.L.D.A(Unknown Source)
at net.minecraft.L.H.I(Unknown Source)
at net.minecraft.L.A.run(Unknown Source)
java.lang.NullPointerException
at net.minecraft.L.D.A(Unknown Source)
at net.minecraft.L.H.I(Unknown Source)
at net.minecraft.L.A.run(Unknown Source)
java.lang.NullPointerException
at net.minecraft.L.D.A(Unknown Source)
at net.minecraft.L.H.I(Unknown Source)
at net.minecraft.L.A.run(Unknown Source)

java.lang.NullPointerException
at java.util.Hashtable.hash(Unknown Source)
at java.util.Hashtable.get(Unknown Source)
at java.util.Properties.getProperty(Unknown Source)
at java.util.Properties.getProperty(Unknown Source)
at net.minecraft.C.ogb.D(Unknown Source)
at net.minecraft.M.hrl.‹init›(Unknown Source)
at net.minecraft.client.Minecraft.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

Stopping!
Exception in thread «AWT-EventQueue-0» java.lang.NullPointerException: component argument pData
at sun.java2d.windows.GDIWindowSurfaceData.initOps(Native Method)
at sun.java2d.windows.GDIWindowSurfaceData.‹init›(Unknown Source)
at sun.java2d.windows.GDIWindowSurfaceData.createData(Unknown Source)
at sun.java2d.d3d.D3DScreenUpdateManager.getGdiSurface(Unknown Source)
at sun.java2d.d3d.D3DScreenUpdateManager.createGraphics(Unknown Source)
at sun.awt.windows.WComponentPeer.getGraphics(Unknown Source)
at java.awt.Component.getGraphics(Unknown Source)
at sun.awt.RepaintArea.paint(Unknown Source)
at sun.awt.windows.WComponentPeer.handleEvent(Unknown Source)
at java.awt.Component.dispatchEventImpl(Unknown Source)
at java.awt.Container.dispatchEventImpl(Unknown Source)
at java.awt.Component.dispatchEvent(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$200(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.awt.EventQueue$4.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

SoundSystem shutting down…

Author: Paul Lamb, www.paulscode.com

Exception in Thread AWT-EventQueue-0 java.lang.NullPointerException

The «AWT-EventQueue-0» java.lang.NullPointerException exception occurs when we work with Java AWT package methods, and a null value is passed to any method. This tutorial demonstrates how to solve this NullPointerException in Java.

Exception in thread «AWT-EventQueue-0» java.lang.NullPointerException in Java

The «AWT-EventQueue-0» java.lang.NullPointerException occurs when we pass a null value to the AWT package. The NullPointerException exception is the most common in Java.

The NullPointerException occurs when any of the following conditions meet.

1. When accessing and modifying the null object field.
2. When we invoke a method from a null object.
3. When accessing and modifying the slots of the null object.
4. When taking the length of any null array.
5. When we try to synchronize over a null object.
6. When we are throwing a null value.

Let’s try an example that will throw the «AWT-EventQueue-0» java.lang.NullPointerException in Java.

The code above is about a simple game with a cow standing, and the cow will start moving on pressing the button. It will throw the «AWT-EventQueue-0» java.lang.NullPointerException because the AWT method new ImageIcon(getClass().getResource()) is getting a null entry.

The output for this code is:

We can solve this issue by moving the images to the class folder path. We can also remove the / as Windows use \ for path in Java.

And if it is still not working, we can give the full path to the images. Further explanations are commented-out in the code above.

Sheeraz is a Doctorate fellow in Computer Science at Northwestern Polytechnical University, Xian, China. He has 7 years of Software Development experience in AI, Web, Database, and Desktop technologies. He writes tutorials in Java, PHP, Python, GoLang, R, etc., to help beginners learn the field of Computer Science.

Источник

Exception in thread «AWT-EventQueue-0» java.lang.NullPointerException

there are no visible error in the syntax but when i run the application i keep getting the following error. i have been trying to fix it for hours and simply cant find the problem. the error that appears when running is;

Exception in thread «AWT-EventQueue-0» java.lang.NullPointerException
at javax.swing.JComboBox.setModel(JComboBox.java:292)
at Application.UserManagement.initComponents(UserManagement.java:234)
at Application.UserManagement. (UserManagement.java:52)
at Application.UserManagement$7.run(UserManagement.java:448)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
BUILD SUCCESSFUL (total time: 1 second)

hopefully somone can help

9 Contributors 14 Replies 32K Views 3 Years Discussion Span Latest Post 9 Years Ago Latest Post by bguild

If you read the messages they tell you at which line you get the error and what the error is.
You are using something which is null

It seems that you are setting a null model for ComboBox in your initComponents() method (which is not listed in the code you’ve shown us).
Check your code at line 292 as shown in the error log.

. and next time please use [code] tags for your code

Thrown when an application attempts to use null in a case where an object is required. These include:
* Calling the instance method of a null object.
* Accessing or modifying the field of a null object.
* Taking the length of null as if it were …

Why are you talking about editing the «fixed Java classes»? The error is in your code. The error messages relate to a single error and show the sequence of calls (starting deep in the Swing event handler), via your faulty code, and maybe back into a Java API method before …

If you read the messages they tell you at which line you get the error and what the error is.
You are using something which is null

yeah i am unable to locate the thing that is null, and the errors are inside the java fixed classes which i have in no way edited.

here is the syntax from my mainGUI. does it show where the NullPointer is?

It seems that you are setting a null model for ComboBox in your initComponents() method (which is not listed in the code you’ve shown us).
Check your code at line 292 as shown in the error log.

. and next time please use [code] tags for your code

now i am getting a new set of error codes, i am unable to edit anything within the fixed java classes.

Exception in thread «AWT-EventQueue-0» java.lang.NullPointerException
at Application.UserManagement.showUsersDetails(UserManagement.java:121)
at Application.UserManagement.cmbUsersClicked(UserManagement.java:449)
at Application.UserManagement.access$000(UserManagement.java:35)
at Application.UserManagement$1.actionPerformed(UserManagement.java:268)
at javax.swing.JComboBox.fireActionEvent(JComboBox.java:1240)
at javax.swing.JComboBox.setSelectedItem(JComboBox.java:567)
at javax.swing.JComboBox.setSelectedIndex(JComboBox.java:603)
at Application.UserManagement. (UserManagement.java:65)
at Application.UserManagement$7.run(UserManagement.java:479)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)

A NullPointerException is

Thrown when an application attempts to use null in a case where an object is required. These include:
* Calling the instance method of a null object.
* Accessing or modifying the field of a null object.
* Taking the length of null as if it were an array.
* Accessing or modifying the slots of null as if it were an array.
* Throwing null as if it were a Throwable value.

Check your showUserDetails method for one of this cases.

Hope this helps,
GL

Why are you talking about editing the «fixed Java classes»? The error is in your code. The error messages relate to a single error and show the sequence of calls (starting deep in the Swing event handler), via your faulty code, and maybe back into a Java API method before the error is detected. However, the fault will be in the few lines of your code that are listed, specifically:
at Application.UserManagement.showUsersDetails(UserManagement.java:121)
Somewhere on that line is an uninitialised variable or a method call that has returned null. If you don’t know which it is, try printing each and every value on that line to System.out

yeah i am unable to locate the thing that is null, and the errors are inside the java fixed classes which i have in no way edited.

No you were too lazy to read the messages, as I told you. That is why you couldn’t locate the error.:

Exception in thread «AWT-EventQueue-0» java.lang.NullPointerException
at javax.swing.JComboBox.setModel(JComboBox.java:292)
at Application.UserManagement.initComponents(UserManagement.java:234)
at Application.UserManagement. (UserManagement.java:52)
at Application.UserManagement$7.run(UserManagement.java:448)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:597)
at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:269)
at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:184)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:174)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:169)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:161)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:122)
BUILD SUCCESSFUL (total time: 1 second)

Did I have to point that out to you? When you get any error, don’t you even bother to read it, or just post the error and expect others to do it for you?

If you still can’t fix it, then point out at the code where that line is. Although the problem is that you are using something which is null (you haven’t initialized something) as stated by the exception and other posters:

Источник

Hello I’m a new programmer at an high school level as a result I do not know much about programming and am getting quite a few errors which have been resolved while others I completely do not understand. I am to make a simple Check Box selection program where the user gets to pick between a variety of choices and depending on their action the image changes. The program itself compiles perfectly but when I run it however it gives me some complications. Here is my program:

package components;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Workshop extends JPanel
                      implements ItemListener {
JCheckBox winterhatButton;
JCheckBox sportshatButton;
JCheckBox santahatButton;
JCheckBox redshirtButton;
JCheckBox brownshirtButton;
JCheckBox suitButton;
JCheckBox denimjeansButton;
JCheckBox blackpantsButton;
JCheckBox khakipantsButton;


    StringBuffer choices;
JLabel pictureLabel;

public Workshop() {
    super(new BorderLayout());

    //Create the check boxes.
    winterhatButton = new JCheckBox("Winter Hat");
    winterhatButton.setMnemonic(KeyEvent.VK_Q);


    sportshatButton = new JCheckBox("Sports Hat");
    sportshatButton.setMnemonic(KeyEvent.VK_W);


    santahatButton = new JCheckBox("Santa hat");
    santahatButton.setMnemonic(KeyEvent.VK_E);


    redshirtButton = new JCheckBox("Red Shirt");
    redshirtButton.setMnemonic(KeyEvent.VK_R);


    brownshirtButton = new JCheckBox("Brown Shirt");
    brownshirtButton.setMnemonic(KeyEvent.VK_T);


    suitButton = new JCheckBox("Suit");
    suitButton.setMnemonic(KeyEvent.VK_Y);


    suitButton = new JCheckBox("Denim Jeans");
    suitButton.setMnemonic(KeyEvent.VK_U);


    blackpantsButton = new JCheckBox("Black Pants");
    blackpantsButton.setMnemonic(KeyEvent.VK_I);


    khakipantsButton = new JCheckBox("Khaki Pants");
    khakipantsButton.setMnemonic(KeyEvent.VK_O);



    //Register a listener for the check boxes.

    winterhatButton.addItemListener(this);
    sportshatButton.addItemListener(this);
    santahatButton.addItemListener(this);
    redshirtButton.addItemListener(this);
    brownshirtButton.addItemListener(this);
    suitButton.addItemListener(this);
    denimjeansButton.addItemListener(this);
    blackpantsButton.addItemListener(this);
    khakipantsButton.addItemListener(this);


    //Indicates
    choices = new StringBuffer("---------");


    //Set up the picture label
    pictureLabel = new JLabel();
    pictureLabel.setFont(pictureLabel.getFont().deriveFont(Font.ITALIC));
    updatePicture();

     //Put the check boxes in a column in a panel
    JPanel checkPanel = new JPanel(new GridLayout(0, 1));
    checkPanel.add(winterhatButton);
    checkPanel.add(sportshatButton);
    checkPanel.add(santahatButton);
    checkPanel.add(redshirtButton);
    checkPanel.add(brownshirtButton);
    checkPanel.add(suitButton);
    checkPanel.add(denimjeansButton);
    checkPanel.add(blackpantsButton);
    checkPanel.add(khakipantsButton);


    add(checkPanel, BorderLayout.LINE_START);
    add(pictureLabel, BorderLayout.CENTER);
    setBorder(BorderFactory.createEmptyBorder(20,20,20,20));
}


    /** Listens to the check boxes. */
public void itemStateChanged(ItemEvent e) {
    int index = 0;
    char c = '-';
    Object source = e.getItemSelectable();

    if (source == winterhatButton) {
        index = 0;
        c = 'q';
    } else if (source == sportshatButton) {
        index = 1;
        c = 'w';
    } else if (source == santahatButton) {
        index = 2;
        c = 'e';
    } else if (source == redshirtButton) {
        index = 3;
        c = 'r';
    } else if (source == brownshirtButton) {
        index = 4;
        c = 't';
    } else if (source == suitButton) {
        index = 5;
        c = 'y';
    } else if (source == denimjeansButton) {
        index = 6;
        c = 'u';
    } else if (source == blackpantsButton) {
        index = 7;
        c = 'i';
    } else if (source == khakipantsButton) {
        index = 8;
        c = 'o';
    } 


    if (e.getStateChange() == ItemEvent.DESELECTED) {
        c = '-';
    }

    //Apply the change to the string.
    choices.setCharAt(index, c);

    updatePicture();
}


protected void updatePicture() {
    //Get the icon corresponding to the image.
    ImageIcon icon = createImageIcon(
                                "images/bear/bear-"
                                + choices.toString()
                                + ".gif");
    pictureLabel.setIcon(icon);
    pictureLabel.setToolTipText(choices.toString());
    if (icon == null) {
        pictureLabel.setText("Missing Image");
    } else {
        pictureLabel.setText(null);
    }
}

/** Returns an ImageIcon, or null if the path was invalid. */
protected static ImageIcon createImageIcon(String path) {
    java.net.URL imgURL = Workshop.class.getResource(path);
    if (imgURL != null) {
        return new ImageIcon(imgURL);
    } else {
        System.err.println("Couldn't find file: " + path);
        return null;
    }
}

  private static void createAndShowGUI() {
    //Create and set up the window.
    JFrame frame = new JFrame("Build a Bear at Safeer's Workshop!");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //Create and set up the content pane.
    JComponent newContentPane = new Workshop();
    newContentPane.setOpaque(true); //content panes must be opaque
    frame.setContentPane(newContentPane);

    //Display the window.
    frame.pack();
    frame.setVisible(true);
}

public static void main(String[] args) {
    //Schedule a job for the event-dispatching thread:
    //creating and showing this application's GUI.
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            createAndShowGUI();
        }
    });
}
}

Well up to this part it runs smoothly and complies but when I proceed to run the program I get this error.

> run components.Workshop
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at components.Workshop.<init>(Workshop.java:75)
at components.Workshop.createAndShowGUI(Workshop.java:195)
at components.Workshop.access$0(Workshop.java:189)
at components.Workshop$1.run(Workshop.java:209)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
at java.awt.EventQueue.access$000(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.awt.EventQueue$3.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.ProtectionDomain$1.doIntersectionPrivilege(Unknown Source)
at java.awt.EventQueue.dispatchEvent(Unknown Source)
at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
at java.awt.EventDispatchThread.run(Unknown Source)

Might be a silly mistake however I cant seem to figure this out. Please Help and thank you

     Here is the line that generates that error 
     private void jButtonSendActionPerformed(java.awt.event.ActionEvent evt)   {                                                
    // TODO add your handling code here:
    String message;
    if(messageBox.getText().length() > 0){
        message  =  messageBox.getText();
        chatBox.append(message+"n"); 
        printStream.println(message);//this line 
        printStream.flush();
        //printStream.close();
        messageBox.setText("");
    }
} 

The "AWT-EventQueue-0" java.lang.NullPointerException exception occurs when we work with Java AWT package methods, and a null value is passed to any method. This tutorial demonstrates how to solve this NullPointerException in Java.

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException in Java

The "AWT-EventQueue-0" java.lang.NullPointerException occurs when we pass a null value to the AWT package. The NullPointerException exception is the most common in Java.

The NullPointerException occurs when any of the following conditions meet.

1. When accessing and modifying the null object field.
2. When we invoke a method from a null object.
3. When accessing and modifying the slots of the null object.
4. When taking the length of any null array.
5. When we try to synchronize over a null object.
6. When we are throwing a null value.

Let’s try an example that will throw the "AWT-EventQueue-0" java.lang.NullPointerException in Java.

package delftstack;

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.util.Timer;

@SuppressWarnings("serial")

public class Example extends JFrame implements ActionListener , KeyListener {

    static Dimension Screen_Size = new         Dimension(Toolkit.getDefaultToolkit().getScreenSize());
    Insets Scan_Max = Toolkit.getDefaultToolkit().getScreenInsets(getGraphicsConfiguration());
    int Task_Bar_Size = Scan_Max.bottom;
    static JFrame Start_Screen = new JFrame("Start Screen");
    static JFrame Game_Frame = new JFrame("Begin the Game!");
    static JLabel Cow_Label = new JLabel();
    static int Sky_Int = 1;
    static JLabel Sky_Label = new JLabel();
    static int SECONDS = 1;
    static boolean IS_Pressed = false;
    public static void main(String[] args) {
        new Example();

    }
    public Example() {

        JPanel Buttons_Panel = new JPanel();
        Buttons_Panel.setLayout(null);
        Start_Screen.setSize(new Dimension(Screen_Size.width - getWidth(), Screen_Size.height - Task_Bar_Size - getHeight()));
        Start_Screen.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        Start_Screen.setVisible(true);
        System.out.println(Start_Screen.getSize());

        //buttons

        JButton Start_Button = new JButton("Start");
        Start_Button.addActionListener(this);
        Start_Button.setSize((int) Start_Screen.getWidth()/7, (int) (Start_Screen.getHeight()/15.36));
        Start_Button.setBounds((Start_Screen.getWidth()/2) - Start_Button.getWidth()/2,((int)Start_Screen.getHeight()/2) - Start_Button.getHeight(),Start_Button.getWidth(),Start_Button.getHeight());
        Start_Button.setActionCommand("Start");

        Buttons_Panel.add(Start_Button);
        Start_Screen.add(Buttons_Panel);
    }
    @Override
    public void actionPerformed(ActionEvent Action_Event) {
        Object CMD_Object =  Action_Event.getActionCommand();
        if(CMD_Object == "Start") {
            Start_Screen.setVisible(false);
            //  getClass().getResource("/cow.png") and getClass().getResource("/grass.png") is giving null
            // because there is no image in folder named cow.png or grass.png
            ImageIcon Cow_Image = new ImageIcon(getClass().getResource("/cow.png"));
            ImageIcon Grass_Image = new   ImageIcon(getClass().getResource("/grass.png"));

            Game_Frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            Game_Frame.setSize(Start_Screen.getSize());
            Game_Frame.setVisible(true);
            JPanel Demo_Panel = new JPanel();
            Demo_Panel.setBackground(Color.white);
            Demo_Panel.setLayout(null);
            Demo_Panel.setFocusable(true);
            Game_Frame.add(Demo_Panel);
            Demo_Panel.addKeyListener(this);
            Cow_Label.setBounds( (Start_Screen.getWidth()/2)-105, (Start_Screen.getHeight()/2)-55, 210, 111);
            Cow_Label.setIcon(Cow_Image);
            Demo_Panel.add(Cow_Label);
            Demo_Panel.setVisible(true);
            Cow_Label.setVisible(true);
            JLabel Grass_Label = new JLabel();
            System.out.println("grass");
            //  getClass().getResource("/Sky.png") will throw a nullpointerexception because there is no image in the folder
            ImageIcon Sky1 = new ImageIcon(getClass().getResource("/Sky.png"));
            Sky_Label.setIcon(Sky1);
            Grass_Label.setIcon(Grass_Image);
            Grass_Label.setBounds(0, ( Start_Screen.getHeight()-308), Start_Screen.getWidth(), 350);
            System.out.println("mOooow");
            Demo_Panel.add(Grass_Label);
            Sky_Label.setBounds(1, 56, 1366, 364);
            Demo_Panel.add(Sky_Label);
            System.out.println("google");
        }

    }
    @Override
    public void keyPressed(KeyEvent Key_Event) {
        int CMD_Int = Key_Event.getKeyCode();
    //  getClass().getResource("/cow moving.gif") will throw a nullpointerexception because there is no image in the folder
        ImageIcon Moving_Cow = new ImageIcon(getClass().getResource("/cow moving.gif"));
        System.out.println(CMD_Int);
        IS_Pressed = true;
        if(CMD_Int == 39){
            System.out.println("Key is Pressed");
            Cow_Label.setIcon(Moving_Cow);
        }
        else if(CMD_Int == 37){

        }
        System.out.println("End");
        while(IS_Pressed==true){
            Timer Wait_Please = new Timer("Wait Please");
            try {
                Wait_Please.wait(1000);
            }
            catch(InterruptedException p){}
            int SKY = 1;
            SKY += 1;
            String SKY_String = "/Sky" + String.valueOf(SKY) + ".png";
            ImageIcon SKy = new ImageIcon(getClass().getResource(SKY_String));
            Sky_Label.setIcon(SKy);
            if(IS_Pressed==false){
            Wait_Please.cancel();
            break;
            }
        }
    }



    @Override
    public void keyReleased(KeyEvent Key_Event) {
    //  getClass().getResource("/cow.png") and getClass().getResource("/grass.png") is giving null
        // because there is no image in folder named cow.png or grass.png
        ImageIcon Cow_Image = new ImageIcon(getClass().getResource("/cow.png"));
        int CMD_Int = Key_Event.getKeyCode();
        IS_Pressed = false;
        if(CMD_Int == 39){
            Cow_Label.setIcon(Cow_Image);
        }
        else if(CMD_Int == 37){
            Cow_Label.setIcon(Cow_Image);
        }
    }
    @Override
    public void keyTyped(KeyEvent c) {
        // TODO Auto-generated method stub
    }
}

The code above is about a simple game with a cow standing, and the cow will start moving on pressing the button. It will throw the "AWT-EventQueue-0" java.lang.NullPointerException because the AWT method new ImageIcon(getClass().getResource()) is getting a null entry.

The output for this code is:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: Cannot invoke "java.net.URL.toExternalForm()" because "location" is null
    at java.desktop/javax.swing.ImageIcon.<init>(ImageIcon.java:234)
    at delftstack.Example.actionPerformed(Example.java:48)
    at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1972)
    at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2313)
...

We can solve this issue by moving the images to the class folder path. We can also remove the / as Windows use \ for path in Java.

And if it is still not working, we can give the full path to the images. Further explanations are commented-out in the code above.

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