FULL PRODUCT VERSION :
java version "1.8.0_66"

A DESCRIPTION OF THE PROBLEM :
When JEdiotPane.setPage is used with a file-Url, a file lock persists.
The setPage function calls internal the function read(InputStream in, Document doc). The read function instantiates an InputStream - this inputstream will never be closed.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
File myFile = new File("ATextFile);
JEditorPane myEditorPane = new JEditorPane();
myEditorPane.setPage(myFile.toURI().toURL());

after this the ATextFile has a file lock until the java program has been closed.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
After using setPage with a file-Url in my expection the file lock should be unlocked after reading the file.
ACTUAL -
The file lock persists, even when the file has been readen.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
File myFile = new File("ATextFile);
JEditorPane myEditorPane = new JEditorPane();
myEditorPane.setPage(myFile.toURI().toURL());

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
The read-function in JEditorPane has private access. There is no way to to extend the JEditorPane.
-< create an own class copy and merge the code of the setPage- and read-function and use:

URL myUrl = p_TextFile.toURI().toURL();
URLConnection myURLConnection = o_Url.openConnection();
InputStream myInputStream = o_URLConnection.getInputStream();

String charset = (String) myEditorPanegetClientProperty("charset");
Reader r = (charset != null) ? new InputStreamReader(myInputStream, charset) :
new InputStreamReader(myInputStream);
myEditorPane.getEditorKit().read(r, myEditorPane.getDocument(), 0);

...

//after all close the myInputStream
myInputStream.close();