Java is cross-platform, most of Java Apps don't need install(unpack and use), don't read/write Windows registry, don't modify any files except it's profile, don't copy any files but it's install folder, they only depents Java VM.
So many desktop apps is based on Java. eg: Azureus, Eclipse, BlogBridge, CrossFTP, jEdit, JamP, etc. And also, there are so many server/web apps based on Java, eg: Tomcat, JBoss, JavaDB/Derby, HSQLDB, H2, db4o, and other FTP/LDAP/DNS server software. We can use web apps to manage our infomations, in many instance, that's better than desktop apps.