Java is "object-oriented" (unlike say Perl4 or Basic) which makes it is easier to build large software systems without them looking like your bedroom |
Java is independent of platform -- runs on all computers |
Java has "threads" built in allowing more than one thing to be done at the same time |
Java supports "exceptions" (nice way of coping with errors which are often inevitable) |
Java has an EXCELLENT security model -- it is by far the safest of any of the common languages |
Java is simpler than C++ |
There are other important technical issues (pointers, garbage collection, good inheritance model) |