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javafilenullpointerexceptionjframerelative-path

Java Create an empty .ser file on resource folder if not exists yet

I want to create an empty .ser file to store an arraylist of objects if not created yet, to use later in program .I will add if not exist check later after figuring out my current problem.I am having a nullpointer exception on my File = new File(etc etc) row.Here is a better explanation with the screenshot.

screenshot and stack traces

edit:Added source codes

/*
* To change this license header, choose License Headers in Project 
Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package dark.rusty;

import java.awt.Color;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.ArrayList;

/**
*
* @author UoD
*/
public class Gui extends javax.swing.JFrame {

/**
 * Creates new form Gui
 */
public Gui() {
    initComponents();
    setLocationRelativeTo(null);
    setTitle("CMS - Dark&Rusty");
    this.getContentPane().setBackground(new Color(190, 190, 190));

    MenuItem a = new MenuItem("temp", 0, 0);
    ArrayList<MenuItem> tempAList = new ArrayList<MenuItem>();
    createFileIFN();

}

private void createFileIFN() {
    try {

        File myFile = new File((this.getClass().getResource("/text/menu.ser").toString());

        if (myFile.createNewFile()) {
            System.out.println("File is created!");
        } else {
            System.out.println("File already exists.");
        }

    } catch (IOException e) {
        e.printStackTrace();
    }
}

private ArrayList<MenuItem> getArrList(File tempFile) {
    ArrayList<MenuItem> items = new ArrayList<MenuItem>();
    MenuItem tempItem;
    try {
        FileInputStream fileIn = new FileInputStream(tempFile);
        ObjectInputStream in = new ObjectInputStream(fileIn);
        tempItem = (MenuItem) in.readObject();
        in.close();
        fileIn.close();
    } catch (IOException i) {
        i.printStackTrace();
    } catch (ClassNotFoundException c) {
        System.out.println("Employee class not found");
        c.printStackTrace();
    }
    return items;
}

private void writeItemtoFile(MenuItem a, File tempFile) {
    try {

        FileOutputStream fos = new FileOutputStream(tempFile);
        ObjectOutputStream oos = new ObjectOutputStream(fos);
        // write object to file
        oos.writeObject(a);
        // closing resources
        oos.close();
        fos.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

/**
 * This method is called from within the constructor to initialize the form.
 * WARNING: Do NOT modify this code. The content of this method is always
 * regenerated by the Form Editor.
 */
@SuppressWarnings("unchecked")
// <editor-fold defaultstate="collapsed" desc="Generated Code">                          
private void initComponents() {

    jPanel1 = new javax.swing.JPanel();
    jButton7 = new javax.swing.JButton();
    jButton8 = new javax.swing.JButton();
    jPanel2 = new javax.swing.JPanel();
    jScrollPane2 = new javax.swing.JScrollPane();
    jList2 = new javax.swing.JList<>();
    jButton6 = new javax.swing.JButton();
    jPanel3 = new javax.swing.JPanel();
    jLabel1 = new javax.swing.JLabel();
    jLabel2 = new javax.swing.JLabel();
    jLabel3 = new javax.swing.JLabel();
    jLabel4 = new javax.swing.JLabel();
    jLabel5 = new javax.swing.JLabel();
    jLabel6 = new javax.swing.JLabel();
    jButton9 = new javax.swing.JButton();
    jButton10 = new javax.swing.JButton();
    jScrollPane3 = new javax.swing.JScrollPane();
    jList3 = new javax.swing.JList<>();

    setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
    setBackground(new java.awt.Color(190, 190, 190));
    setResizable(false);
    setSize(new java.awt.Dimension(800, 600));

    jPanel1.setBackground(new java.awt.Color(190, 190, 190));
    jPanel1.setPreferredSize(new java.awt.Dimension(800, 50));

    jButton7.setIcon(new javax.swing.ImageIcon(getClass().getResource("/images/if_Sidebar_Left_Interface_Menu_Window_1654369.png"))); // NOI18N
    jButton7.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    jButton7.setMargin(new java.awt.Insets(2, 20, 2, 20));
    jButton7.setPreferredSize(new java.awt.Dimension(32, 32));
    jPanel1.add(jButton7);

    jButton8.setIcon(new javax.swing.ImageIcon(getClass().getResource("/images/if_TaskStroke_1737368.png"))); // NOI18N
    jButton8.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    jButton8.setMargin(new java.awt.Insets(2, 20, 2, 20));
    jButton8.setPreferredSize(new java.awt.Dimension(32, 32));
    jPanel1.add(jButton8);

    jPanel2.setBackground(new java.awt.Color(190, 190, 190));

    javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
    jPanel2.setLayout(jPanel2Layout);
    jPanel2Layout.setHorizontalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 800, Short.MAX_VALUE)
    );
    jPanel2Layout.setVerticalGroup(
        jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGap(0, 100, Short.MAX_VALUE)
    );

    jScrollPane2.setPreferredSize(new java.awt.Dimension(300, 120));

    jList2.setBackground(new java.awt.Color(190, 190, 190));
    jList2.setBorder(javax.swing.BorderFactory.createMatteBorder(2, 2, 2, 2, new java.awt.Color(240, 240, 240)));
    jList2.setFont(new java.awt.Font("Rockwell", 1, 14)); // NOI18N
    jList2.setModel(new javax.swing.AbstractListModel<String>() {
        String[] strings = { "Item 1", "Item 2", "Item 3", "Item 4", "Item 5" };
        public int getSize() { return strings.length; }
        public String getElementAt(int i) { return strings[i]; }
    });
    jList2.setSelectionMode(javax.swing.ListSelectionModel.SINGLE_SELECTION);
    jList2.setPreferredSize(new java.awt.Dimension(290, 80));
    jScrollPane2.setViewportView(jList2);

    jButton6.setIcon(new javax.swing.ImageIcon(getClass().getResource("/images/if_Tick_1737369 (1).png"))); // NOI18N
    jButton6.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    jButton6.setPreferredSize(new java.awt.Dimension(32, 32));
    jButton6.addActionListener(new java.awt.event.ActionListener() {
        public void actionPerformed(java.awt.event.ActionEvent evt) {
            jButton6ActionPerformed(evt);
        }
    });

    jPanel3.setBackground(new java.awt.Color(190, 190, 190));
    jPanel3.setPreferredSize(new java.awt.Dimension(290, 136));

    jLabel1.setFont(new java.awt.Font("Poiret One", 1, 24)); // NOI18N
    jLabel1.setForeground(new java.awt.Color(51, 102, 0));
    jLabel1.setText("Kalan:");
    jLabel1.setPreferredSize(new java.awt.Dimension(120, 30));

    jLabel2.setFont(new java.awt.Font("Poiret One", 1, 24)); // NOI18N
    jLabel2.setForeground(new java.awt.Color(204, 0, 51));
    jLabel2.setText("Odenen:");
    jLabel2.setPreferredSize(new java.awt.Dimension(120, 30));

    jLabel3.setFont(new java.awt.Font("Poiret One", 1, 24)); // NOI18N
    jLabel3.setForeground(new java.awt.Color(0, 153, 255));
    jLabel3.setText("0");
    jLabel3.setToolTipText("");
    jLabel3.setPreferredSize(new java.awt.Dimension(120, 30));

    jLabel4.setFont(new java.awt.Font("Poiret One", 1, 24)); // NOI18N
    jLabel4.setForeground(new java.awt.Color(51, 102, 0));
    jLabel4.setText("5.00");
    jLabel4.setPreferredSize(new java.awt.Dimension(120, 30));

    jLabel5.setFont(new java.awt.Font("Poiret One", 1, 24)); // NOI18N
    jLabel5.setForeground(new java.awt.Color(204, 0, 51));
    jLabel5.setText("13.00");
    jLabel5.setPreferredSize(new java.awt.Dimension(120, 30));

    jLabel6.setFont(new java.awt.Font("Poiret One", 1, 24)); // NOI18N
    jLabel6.setForeground(new java.awt.Color(0, 153, 255));
    jLabel6.setText("İptal:");
    jLabel6.setPreferredSize(new java.awt.Dimension(120, 30));

    javax.swing.GroupLayout jPanel3Layout = new javax.swing.GroupLayout(jPanel3);
    jPanel3.setLayout(jPanel3Layout);
    jPanel3Layout.setHorizontalGroup(
        jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel3Layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(jPanel3Layout.createSequentialGroup()
                    .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 40, Short.MAX_VALUE)
                    .addComponent(jLabel4, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGroup(jPanel3Layout.createSequentialGroup()
                    .addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jLabel5, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel3Layout.createSequentialGroup()
                    .addComponent(jLabel6, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addComponent(jLabel3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)))
            .addContainerGap())
    );
    jPanel3Layout.setVerticalGroup(
        jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(jPanel3Layout.createSequentialGroup()
            .addContainerGap()
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jLabel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jLabel4, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jLabel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jLabel5, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 13, Short.MAX_VALUE)
            .addGroup(jPanel3Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                .addComponent(jLabel3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addComponent(jLabel6, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
            .addContainerGap())
    );

    jButton9.setIcon(new javax.swing.ImageIcon(getClass().getResource("/images/if_Dollar_1737376(1).png"))); // NOI18N
    jButton9.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    jButton9.setPreferredSize(new java.awt.Dimension(32, 32));

    jButton10.setIcon(new javax.swing.ImageIcon(getClass().getResource("/images/if_Wrong_1737371.png"))); // NOI18N
    jButton10.setHorizontalTextPosition(javax.swing.SwingConstants.CENTER);
    jButton10.setPreferredSize(new java.awt.Dimension(32, 32));

    jScrollPane3.setPreferredSize(new java.awt.Dimension(300, 120));

    jList3.setBackground(new java.awt.Color(190, 190, 190));
    jList3.setBorder(javax.swing.BorderFactory.createMatteBorder(2, 2, 2, 2, new java.awt.Color(240, 240, 240)));
    jList3.setFont(new java.awt.Font("Rockwell", 1, 14)); // NOI18N
    jList3.setSelectionMode(javax.swing.ListSelectionModel.SINGLE_SELECTION);
    jList3.setPreferredSize(new java.awt.Dimension(290, 80));
    jScrollPane3.setViewportView(jList3);

    javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
    getContentPane().setLayout(layout);
    layout.setHorizontalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        .addGroup(layout.createSequentialGroup()
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGroup(layout.createSequentialGroup()
                    .addGap(6, 6, 6)
                    .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                        .addGroup(layout.createSequentialGroup()
                            .addComponent(jButton6, javax.swing.GroupLayout.PREFERRED_SIZE, 32, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                            .addComponent(jButton9, javax.swing.GroupLayout.PREFERRED_SIZE, 32, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addGroup(layout.createSequentialGroup()
                            .addGap(0, 0, Short.MAX_VALUE)
                            .addComponent(jButton10, javax.swing.GroupLayout.PREFERRED_SIZE, 32, javax.swing.GroupLayout.PREFERRED_SIZE)))
                    .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                    .addComponent(jScrollPane3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGap(10, 10, 10)))
            .addGap(0, 0, Short.MAX_VALUE))
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
            .addComponent(jPanel3, javax.swing.GroupLayout.PREFERRED_SIZE, 300, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addContainerGap())
    );
    layout.setVerticalGroup(
        layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
        .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
            .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING, false)
                    .addComponent(jButton6, javax.swing.GroupLayout.PREFERRED_SIZE, 32, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jScrollPane2, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jButton9, javax.swing.GroupLayout.PREFERRED_SIZE, 32, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                        .addComponent(jButton10, javax.swing.GroupLayout.PREFERRED_SIZE, 32, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addComponent(jScrollPane3, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
            .addComponent(jPanel3, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED, 182, Short.MAX_VALUE)
            .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, 50, javax.swing.GroupLayout.PREFERRED_SIZE))
    );

    pack();
}// </editor-fold>                        

private void jButton6ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    // TODO add your handling code here:
}                                        

/**
 * @param args the command line arguments
 */
public static void main(String args[]) {
    /* Set the Nimbus look and feel */
    //<editor-fold defaultstate="collapsed" desc=" Look and feel setting code (optional) ">
    /* If Nimbus (introduced in Java SE 6) is not available, stay with the default look and feel.
     * For details see http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html 
     */
    try {
        for (javax.swing.UIManager.LookAndFeelInfo info : javax.swing.UIManager.getInstalledLookAndFeels()) {
            if ("Nimbus".equals(info.getName())) {
                javax.swing.UIManager.setLookAndFeel(info.getClassName());
                break;
            }
        }
    } catch (ClassNotFoundException ex) {
        java.util.logging.Logger.getLogger(Gui.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (InstantiationException ex) {
        java.util.logging.Logger.getLogger(Gui.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (IllegalAccessException ex) {
        java.util.logging.Logger.getLogger(Gui.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    } catch (javax.swing.UnsupportedLookAndFeelException ex) {
        java.util.logging.Logger.getLogger(Gui.class.getName()).log(java.util.logging.Level.SEVERE, null, ex);
    }
    //</editor-fold>

    /* Create and display the form */
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            new Gui().setVisible(true);
        }
    });
}

// Variables declaration - do not modify                     
private javax.swing.JButton jButton10;
private javax.swing.JButton jButton6;
private javax.swing.JButton jButton7;
private javax.swing.JButton jButton8;
private javax.swing.JButton jButton9;
private javax.swing.JLabel jLabel1;
private javax.swing.JLabel jLabel2;
private javax.swing.JLabel jLabel3;
private javax.swing.JLabel jLabel4;
private javax.swing.JLabel jLabel5;
private javax.swing.JLabel jLabel6;
private javax.swing.JList<String> jList2;
private javax.swing.JList<String> jList3;
private javax.swing.JPanel jPanel1;
private javax.swing.JPanel jPanel2;
private javax.swing.JPanel jPanel3;
private javax.swing.JScrollPane jScrollPane2;
private javax.swing.JScrollPane jScrollPane3;
// End of variables declaration                   
}
Solution 
  • this.getClass().getResource("/text/menu.ser")

    will return null if "/text/menu.ser" does not exists. Consequently,

    this.getClass().getResource("/text/menu.ser").toString()

    will result in a NullPointerException.

    Moreover, getResource returns an URL instance and an URL's string reprensentation (e.g. file:/home/user3524633/text/menu.ser) is not the same as a local file system path (which is what you want to use with the File constructor).

    Why are you using getResource in the first place? Are you trying to determine a path relative to your application's classes?