NullPointerException in Applet

[teenIce]

Hi all,

Thanks in advance. I am new at Java. Currently I'm having two java files one is applet. when i try to preview the applet i get an error like this :

java.lang.NullP ointerException
at java.util.Hasht able.put(Unknow n Source)
at javax.swing.JEd itorPane.regist erEditorKitForC ontentType(Unkn own Source)
at javax.swing.JEd itorPane.regist erEditorKitForC ontentType(Unkn own Source)
at javax.swing.JEd itorPane.loadDe faultKitsIfNece ssary(Unknown Source)
at javax.swing.JEd itorPane.getKit TypeRegistry(Un known Source)
at javax.swing.JEd itorPane.getEdi torKitClassName ForContentType( Unknown Source)
at javax.swing.JTe xtPane.<init>(U nknown Source)

what i'm doing wrong?pls help me guys...thanks

[JosAH]

Can you show a bit of (relevant) code please? btw, I changed your topic titile
to something more to the point.

kind regards,

Jos

[nickyeng]

because you pointed to hashtable that doesn't have the key ?

check your code that use that hashtable ...

[teenIce]

Hi all,

Thanks Josah. Erm, what do you mean by hashtable nick?I don't understand..Sor ry.btw this is my code that call JTextPane

code :

private JTextArea textArea = null;
private JTextPane resultArea = null;
private JComboBox langBox = null;

private Map<Language, ConfigurationDi alog> configDialogs = new HashMap<Languag e, ConfigurationDi alog>();
public void createAndShowGU I(String inputText) {
JFrame frame = new JFrame("Test");
frame.setDefaul tCloseOperation (JFrame.HIDE_ON _CLOSE);

textArea = new JTextArea(input Text);
// TODO: wrong line number is displayed for lines that are wrapped automatically:
textArea.setLin eWrap(true);
textArea.setWra pStyleWord(true );
resultArea = new JTextPane();
resultArea.setC ontentType("tex t/html");
resultArea.setT ext("Results will appear here");
JLabel label = new JLabel("Please type or paste text to check in the top area");
JButton button = new JButton("Check text");
button.setMnemo nic('c');
button.addActio nListener(this) ;

[r035198x]

Hi all,

Thanks Josah. Erm, what do you mean by hashtable nick?I don't understand..Sor ry.btw this is my code that call JTextPane

code :

private JTextArea textArea = null;
private JTextPane resultArea = null;
private JComboBox langBox = null;

private Map<Language, ConfigurationDi alog> configDialogs = new HashMap<Languag e, ConfigurationDi alog>();
public void createAndShowGU I(String inputText) {
JFrame frame = new JFrame("Test");
frame.setDefaul tCloseOperation (JFrame.HIDE_ON _CLOSE);

textArea = new JTextArea(input Text);
// TODO: wrong line number is displayed for lines that are wrapped automatically:
textArea.setLin eWrap(true);
textArea.setWra pStyleWord(true );
resultArea = new JTextPane();
resultArea.setC ontentType("tex t/html");
resultArea.setT ext("Results will appear here");
JLabel label = new JLabel("Please type or paste text to check in the top area");
JButton button = new JButton("Check text");
button.setMnemo nic('c');
button.addActio nListener(this) ;

1.) Please use code tags when posting code.
2.) If you look at that stacktrace again, you'll see that it tells you the exact line number where that exception was thrown. That line and the code lines around it are the relevant code that Jos asked you to post.

[teenIce]

oh...thanks guys,

ok...here is the code that is relevant to the trace and the full trace

trace :

Java Plug-in 1.6.0_02
Using JRE version 1.6.0_02 Java HotSpot(TM) Client VM
User home directory = C:\Documents and Settings\Administrator
network: Loading user-defined proxy configuration ...
network: Done.
network: Loading proxy configuration from Internet Explorer ...
network: Done.
network: Loading direct proxy configuration ...
network: Done.
network: Proxy Configuration: No proxy


----------------------------------------------------
c:   clear console window
f:   finalize objects on finalization queue
g:   garbage collect
h:   display this help message
l:   dump classloader list
m:   print memory usage
o:   trigger logging
p:   reload proxy configuration
q:   hide console
r:   reload policy configuration
s:   dump system and deployment properties
t:   dump thread list
v:   dump thread stack
x:   clear classloader cache
0-5: set trace level to <n>
----------------------------------------------------

liveconnect: Invoking JS method: document
liveconnect: Invoking JS method: URL
basic: Referencing classloader: sun.plugin.ClassLoaderInfo@12498b5, refcount=1
basic: Added progress listener: sun.plugin.util.GrayBoxPainter@f5da06
basic: Loading applet ...
basic: Initializing applet ...
basic: Starting applet ...
basic: completed perf rollup
liveconnect: Invoking method: public void test.check(java.lang.String)
liveconnect: Needs conversion: java.lang.String --> java.lang.String
java.lang.NullPointerException
	at java.util.Hashtable.put(Unknown Source)
	at javax.swing.JEditorPane.registerEditorKitForContentType(Unknown Source)
	at javax.swing.JEditorPane.registerEditorKitForContentType(Unknown Source)
	at javax.swing.JEditorPane.loadDefaultKitsIfNecessary(Unknown Source)
	at javax.swing.JEditorPane.getKitTypeRegistry(Unknown Source)
	at javax.swing.JEditorPane.getEditorKitClassNameForContentType(Unknown Source)
	at javax.swing.JTextPane.<init>(Unknown Source)
	at mypack.Main.createAndShowGUI(main.java:84)
	at mypack.Main.openGui(main.java:236)
	at test.check(test.java:27)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at sun.plugin.javascript.JSInvoke.invoke(Unknown Source)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at sun.plugin.javascript.JSClassLoader.invoke(Unknown Source)
	at sun.plugin.com.MethodDispatcher.invoke(Unknown Source)
	at sun.plugin.com.DispatchImpl.invokeImpl(Unknown Source)
	at sun.plugin.com.DispatchImpl$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.plugin.com.DispatchImpl.invoke(Unknown Source)
java.lang.Exception: java.lang.NullPointerException
	at sun.plugin.com.DispatchImpl.invokeImpl(Unknown Source)
	at sun.plugin.com.DispatchImpl$1.run(Unknown Source)
	at java.security.AccessController.doPrivileged(Native Method)
	at sun.plugin.com.DispatchImpl.invoke(Unknown Source)

and the relevant code is :

private JTextArea textArea = null;
  private JTextPane resultArea = null;
  private JComboBox langBox = null;
 
  private Map<Language, ConfigurationDialog> configDialogs = new HashMap<Language, ConfigurationDialog>();

   public Main() {
  }

  public void createAndShowGUI(String inputText) {
    JFrame frame = new JFrame("Grammar Check Tool");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    textArea = new JTextArea(inputText);
    // TODO: wrong line number is displayed for lines that are wrapped automatically:
    textArea.setLineWrap(true);
    textArea.setWrapStyleWord(true);
 	JTextPane resultArea = new JTextPane();
    resultArea.setContentType("text/html");
    resultArea.setText("Results will appear here");   
	JLabel label = new JLabel("Please type or paste text to check in the top area");
    JButton button = new JButton("Check text");
    button.setMnemonic('c'); 
    button.addActionListener(this);

    JButton configButton = new JButton(OPTIONS_BUTTON);
    configButton.setMnemonic('o'); 
    configButton.addActionListener(this);

    JPanel panel = new JPanel();
    panel.setLayout(new GridBagLayout());
    GridBagConstraints buttonCons = new GridBagConstraints();
    buttonCons.gridx = 0;
    buttonCons.gridy = 0;
    panel.add(button, buttonCons);
    buttonCons.gridx = 1;
    buttonCons.gridy = 0;
    panel.add(new JLabel("  "), buttonCons);
    buttonCons.gridx = 2;
    buttonCons.gridy = 0;
  
    buttonCons.gridx = 3;
    buttonCons.gridy = 0;
    buttonCons.insets = new Insets(0, 10, 0, 0);
    //panel.add(configButton, buttonCons);

    Container contentPane = frame.getContentPane();
    GridBagLayout gridLayout = new GridBagLayout();
    contentPane.setLayout(gridLayout);
    GridBagConstraints cons = new GridBagConstraints();
    cons.fill = GridBagConstraints.BOTH;
    cons.weightx = 10.0f;
    cons.weighty = 10.0f;
    cons.gridx = 0;
    cons.gridy = 0;
    contentPane.add(new JScrollPane(textArea), cons);
    cons.gridy = 1;
    cons.weighty = 5.0f;
    contentPane.add(new JScrollPane(resultArea), cons);

    cons.fill = GridBagConstraints.NONE;
    cons.gridx = 0;
    cons.gridy = 2;
    cons.weighty = 0.0f;
    cons.insets = new Insets(3,3,3,3);
    //cons.fill = GridBagConstraints.NONE;
    contentPane.add(label, cons);
    cons.gridy = 3;
    contentPane.add(panel, cons);
    
    frame.pack();
    frame.setSize(600, 600);
    frame.setVisible(true);
  }

Thanks for your help...

[JosAH]

Which of the lines is line #84 in method createAndShowGU I()?

kind regards,

Jos

[teenIce]

Which of the lines is line #84 in method createAndShowGU I()?

kind regards,

Jos

resultArea = new JTextPane();

regards,
teenICe

[r035198x]

Here is one nit that is a good recipe for brewing nullpointers.

You have [CODE=java] JTextPane resultArea = new JTextPane();[/CODE] inside your createGUI method. This hides the resultArea already defined in the class using [CODE=java]private JTextPane resultArea = null;[/CODE]. The later resultArea variable is thus probably not being initialized properly.

[JosAH]

resultArea = new JTextPane();

regards,
teenICe

Got it: you have a member variable resultArea but you also define a local variable
with the same name; it effectively hides the member variable which will remain
null all the time. Don't define that local variable.

kind regards,

Jos

[r035198x]

resultArea = new JTextPane();

regards,
teenICe

Something is rotten in the state of Denmark here ...

[teenIce]

so..its means I must comment out this code :

 private JTextPane resultArea = null;

thanks guys...
I'll try it... :)

[r035198x]

so..its means I must comment out this code :

 private JTextPane resultArea = null;

thanks guys...
I'll try it... :)

That's not what Jos said. Read it again. Just don't define a new variable for it in your method.

@Jos, why would he get a nullpointer at that line? I'd expect the nullpointer to occur somewhere else, most likely outside the createGUI method.

[teenIce]

No...I try to comment out the code but still have same error...I don't know what I'm doing wrong.Hmm...may be I'm not understand enough.Can you guys explain it to me??Please...

Thanks in advance..

[r035198x]

No...I try to comment out the code but still have same error...I don't know what I'm doing wrong.Hmm...may be I'm not understand enough.Can you guys explain it to me??Please...

Thanks in advance..

Read the responses again. Commenting out lines of code that give errors does not neccessarily remove the errors.
In your method, you have [CODE=java]JTextPane resultArea = new JTextPane();[/CODE]
Just change that to [CODE=java] resultArea = new JTextPane();[/CODE] like you did with that text area.