The JDT search creates an index for all the sources and the dependent jars. As a jar gets added into the classpath, it is indexed. This operation could take time depending upon the size of the jar. To improve this performance, one can pre-built the index and specify the index for a jar when it gets added into the classpath. This is supported only for jars.
The indexes can be pre generated by the following ways:
The index can be specified as a classpath attribute of the library that is getting added. The index file has to be in a valid URL form. If the index file is not found, JDT generates an index file and uses it for searches.