Most companies prefer someone with certification. If you have a Java certification, it lets potential employers know that you like taking initiative and that you like keeping up to date. This will separate you from other non-certified programmers.
Frameworks
This is essential. If you’ve never worked with a framework, the employer knows that your Java abilities are limited. If you know Struts or JSF it will be a big plus. If you don’t know either one I suggest JSF because it’s not only a framework; it also provides countless tools that make development a lot simpler.
Database Persistence
Another essential tool in the Java world is Hibernate. Every job opening you find, you will see Hibernate. Hibernate is just a tool / API that helps you work with relational databases. If you don’t know it, read up on it. Job openings that don’t ask for Hibernate are rare.
Xml
In every Java job opening, you will find xml. Try to become confirmable with one of these Java parsers: JAXP, Xerces, SAX. These will look great on your CV. Having some experience with a parser is a must.
Tomcat/Jboss
You should know tomcat. You can’t run a Java web application with out it. It’s as essential as knowing JSPs and Servlets. Plus it’s simple and easy to use. Jboss is another keyword that you’ll find in many job openings. Jboss is a j2ee web application server. Very popular and will look great on your resume.
That’s it. If you have all of these in your CV, the chances of getting your dream job go up substantially. Experience plays a big part as well. But if you have a couple of years experience combined with the tools above, employers will be more than eager to snatch you up and pay you a hefty salary.