Bug 26699 Create Jar fails with no warning if jar read-only
Once *.jardesc has been created, if I invoke "Create JAR" from the context menu and the jar file already exists and is read-only, the progress dialog flashes and nothing more happens. Please add check for this condition and at least an error message should be displayed. Even better, ask something like "Jar file read-only, overwrite?" Y/N and overwrite the file on yes (similar to what the option "warn if jar file exists" does).
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarFileExportOperation.java
}
					String javaName= new String(cfReader.sourceFileName());
					Object classFiles= map.get(javaName);
					if (classFiles == null) {
						classFiles= new ArrayList(3);
						map.put(javaName, classFiles);
					}
					((ArrayList)classFiles).add(classFile);
				}
			}		
		}
		return map;
	}
	/**
	 * Creates a file resource handle for the file with the given workspace path.
	 * This method does not create the file resource; this is the responsibility
	 * of <code>createFile</code>.
	 *
	 * @param filePath the path of the file resource to create a handle for
	 * @return the new file resource handle
	 * @see #createFile
	 */
	protected IFile createFileHandle(IPath filePath) {
		if (filePath.isValidPath(filePath.toString()) && filePath.segmentCount() >= 2)
			return JavaPlugin.getWorkspace().getRoot().getFile(filePath);
		else
			return null;
	}
	/**
	 * Creates a folder resource handle for the folder with the given workspace path.