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POTrying to print to JTextArea
 

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  1. POTrying to print to JTextArea
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    <p>I am trying to figure out a way to print to a JTextArea without throwing an exception. Currently I am throwing a NullPointerException but on when I try to print to the JTextArea. I am not sure where it goes wrong or why. Someone please help me. Thank you.</p> <pre><code> import java.awt.EventQueue; import java.util.LinkedList; import java.util.Queue; import java.util.Stack; import javax.swing.JFrame; import javax.swing.JButton; import javax.swing.JLabel; import javax.swing.JScrollPane; import javax.swing.SwingConstants; import javax.swing.JTextField; import javax.swing.JScrollBar; import java.awt.event.ActionListener; import java.awt.event.ActionEvent; import javax.swing.JTextArea; public class TicketLine { private JFrame frame; private JTextArea textArea; public static void main(String[] args) { EventQueue.invokeLater(new Runnable() { public void run() { try { TicketLine window = new TicketLine(); window.frame.setVisible(true); } catch (Exception e) { e.printStackTrace(); } } }); } public TicketLine() { initialize(); } /** * Initialize the contents of the frame. */ private void initialize() { frame = new JFrame(); frame.setBounds(100, 100, 450, 300); frame.setLocationRelativeTo(null); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.getContentPane().setLayout(null); JButton nextButton = new JButton("Next Person"); nextButton.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent arg0) { Queue&lt;String&gt; queue = new LinkedList&lt;String&gt;(); queue.offer("Megan"); queue.offer("Kate"); queue.offer("Conan"); queue.offer("Jay"); queue.offer("Bert"); queue.offer("Ernie"); queue.offer("Mickey"); queue.offer("Goofy"); queue.offer("Optimus"); queue.offer("Megatron"); Stack&lt;String&gt; ticketList = ticketList(); while(queue.size() &gt; 0) // System.out.println(queue.remove() + " wins tickets to " + ticketList.pop()); // NullPointerException HAPPENS HERE! textArea.setText(queue.remove() + "wins tickets to " + ticketList.pop()); } }); nextButton.setBounds(165, 197, 106, 23); frame.getContentPane().add(nextButton); JLabel lblNewLabel = new JLabel("To Display Next Winner Press the Button"); lblNewLabel.setHorizontalAlignment(SwingConstants.CENTER); lblNewLabel.setBounds(90, 156, 245, 30); frame.getContentPane().add(lblNewLabel); JScrollPane scrollPane = new JScrollPane(); scrollPane.setBounds(0, 0, 2, 2); frame.getContentPane().add(scrollPane); JTextArea textArea = new JTextArea(); textArea.setBounds(90, 38, 245, 91); frame.getContentPane().add(textArea); } public static Stack&lt;String&gt; ticketList() { Stack&lt;String&gt; tickets = new Stack&lt;String&gt;(); tickets.push("Olympus Has Fallen"); tickets.push("Jurassic Park"); tickets.push("The Patriot"); tickets.push("Matrix"); tickets.push("Gettysburg"); tickets.push("Gods and Generals"); tickets.push("White House Down"); tickets.add((int) (Math.random() * 5), "Star Wars"); tickets.add((int) (Math.random() * 5), "Star Wars"); tickets.add((int) (Math.random() * 5), "Star Wars"); return tickets; } } </code></pre> <p>Where I have the Quotes I don't have any issues when I switch t around the other way except that it wont print in the JTextArea it prints out the results in Eclipse itself.</p>
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    1. COPost the entire exception (including full call stack)
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    2. COThe process of solving this is **much** more important than the actual solution, since you will surely run up against the NPE again. The lesson to learn is to look closely at the variables used on the line throwing the NPE. One of them is null, and once you find out, backtrack in your code to find out why.
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