Re: Is JTextArea.append(String) really thread safe?

From:

Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net>

Newsgroups:

comp.lang.java.programmer

Date:

Mon, 19 Jul 2010 13:40:07 -0700

Message-ID:

<EK21o.16126$wm1.2298@newsfe01.iad>

On 7/19/2010 1:37 PM, Daniel Pitts wrote:

On 7/19/2010 11:39 AM, markspace wrote:

So here's another thread safety question: is the
JTextArea.append(String) really thread safe? Here's the guts of the
method in question:

public void append(String str) {
Document doc = getDocument();
if (doc != null) {
try {
doc.insertString(doc.getLength(), str, null);
} catch (BadLocationException e) {
}
}
}

Note the call to getDocument() is unsynchronized. What does the
getDocument() method do? It's part of JTextComponent's API:

public Document getDocument() {
return model;
}

Things aren't looking good. Maybe field "model" is declared final or
volatile?

private Document model;

Ouch, it's just private. So, I conclude that the Swing docs lie and
append() is not thread safe. Can anyone show me where I went wrong?

The Document object itself is thread-safe, at least with regards to
insertString see:
<http://download.oracle.com/docs/cd/E17476_01/javase/1.4.2/docs/api/javax/swing/text/Document.html#insertString%28int,%20java.lang.String,%20javax.swing.text.AttributeSet%29>

Sorry, wrong javadoc...
The AbstractDocument class javadoc states that the method is thread safe.
<http://download.oracle.com/docs/cd/E17409_01/javase/6/docs/api/javax/swing/text/AbstractDocument.html#insertString%28int,%20java.lang.String,%20javax.swing.text.AttributeSet%29>

--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>