What version of the JDK is required for ICU4J?
Parts of ICU4J depend on functionality that is only available in JDK 1.4 or later, although some components work under earlier JVMs. All components should be compiled using a Java2 compiler, as even components that run under earlier JVMs can require language features that are only present in Java2. Currently 1.1.x, 1.2.x and 1.3.x JVMs are unsupported and untested, and you use the components on these JVMs at your own risk.