Bug 82804 Jar creation should use less memory
I noticed that the JarWriter will read the entire file it plans to store into memory. An optimization would be to stream the file directly into the JarOutputStream. The only catch is with STORED items which need the CRC32 computed. A penalty could be taken in that case to compute the CRC in a loop and then stream the file.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/jarpackager/JarFileExportOperation.java
return count;
	}
	
	private int getTotalChildCount(IContainer container) {
		IResource[] members;
		try {
			members= container.members();
		} catch (CoreException ex) {
			return 0;
		}
		int count= 0;
		for (int i= 0; i < members.length; i++) {
			if (members[i].getType() == IResource.FILE)
				count++;
			else
				count += getTotalChildCount((IContainer)members[i]);
		}
		return count;
	}
	/**
	 * Exports the passed resource to the JAR file
	 *
	 * @param element the resource or JavaElement to export
	 */
	protected void exportElement(Object element, IProgressMonitor progressMonitor) throws InterruptedException {
		int leadSegmentsToRemove= 1;
		IPackageFragmentRoot pkgRoot= null;
		boolean isInJavaProject= false;
		IResource resource= null;