Re: Is JTextArea.append(String) really thread safe?
On 07/19/2010 10:40 PM, Daniel Pitts wrote:
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) {
}
}
}
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>
Well, technically, somebody could write a separate implementation of
Document without extending AbstractDocument, so the thread-safety should
be part of the interface's contract. More importantly, the two calls on
the document in
doc.insertString(doc.getLength(), str, null);
....aren't synchronized, so I suppose it might happen that the index
returned by getLength() no longer points to the end of the document by
the time insertString() is called, resulting in either a
BadLocationException (which is eaten and results in the append()
operation doing nothing) or an insertion of the string before the end of
the document -- both cases seem to violate the contract of the append()
method.
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