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/ui/jarpackager/JarPackageData.java
* Name: <name of the package>
	 * Sealed: true
	 * <p>
	 * This should only be used if the JAR itself is not sealed.
	 * </p>
	 * 
	 * @return an array of <code>IPackageFragment</code>
	 */
	public IPackageFragment[] getPackagesToSeal() {
		if (fPackagesToSeal == null)
			return new IPackageFragment[0];
		else
			return fPackagesToSeal;
	}
	/**
	 * Gets the packages which should explicitly be unsealed.
	 * The following entry will be added to the manifest file for each package:
	 * Name: <name of the package>
	 * Sealed: false
	 * <p>
	 * This should only be used if the JAR itself is sealed.
	 * </p>
	 * 
	 * @return an array of <code>IPackageFragment</code>
	 */
	public IPackageFragment[] getPackagesToUnseal() {
		if (fPackagesToUnseal == null)
			return new IPackageFragment[0];
		else
			return fPackagesToUnseal;