Today Java provides you lots of job opportunities than any other programming language.
If want to go with Java then, having C language basics can help you a lot as Java language derived some basics structures from C language.
You can take help online by reading online tutorials available. Start to do programs and go with smaller projects. Learn basics and then go with advance one.
There are following sections you should cover if go with java.
1)Basic Java understanding. Why to choose Java today?
2)Internal working on JVM
4)OOps Concept(Class,Object,Inheritence,Method Overloading,Method Overriding etc)
5)Use of static,super and this keywords
5)What is Object class and its methods(toString(),clone() etc)
2)JSP & JSTL