4.12 New JDK Utilities

JDK 1.1 includes a number of new tools. In the discussion of applets above, we've already seen jar for creating JAR archives and javakey for adding digital signatures to JAR archives. In fact, javakey can do much more than that--it is a very flexible tool for managing a database of entities, generating keys and certificates, and generating digital signatures.

serialver is a new tool used in conjunction with object serialization. When an object is deserialized, it is important to verify that the version of the class file for that object matches the version that was used to serialize it. This is done by computing a unique identifier for the class and encoding it in a private variable of the class. When an incompatible change is made to the class, a new unique identifier is computed, and the new value is stored in the private variable. It is the serialver tool that is used to compute this unique identifier.

native2ascii is a tool for programmers who program in a locale that uses a non-ASCII file encoding. The javac compiler can only compile files encoded in ASCII, with all Unicode characters converted to the \uxxxx format. What native2ascii does is to convert its input file to Unicode, and then output that Unicode version as an ASCII file that uses the \u escape for all non-ASCII Unicode characters. After you process a locally-encoded file with native2ascii, javac can compile it.

In addition to the tools described here, JDK 1.1 also includes two new programs, rmic and rmiregistry, that are used in conjunction with Remote Method Invocation. They will be documented in Java Enterprise in a Nutshell.