how to learn Java
Can anyone tell me what do you need to know to have solid knowledge of Java programming language, because there are a lot of job opportunities that ask for solid knowing of Java
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The often-overlooked Java tutorial is a good start:
I'd say everything up to (but not including) the deployment section is 100% essential, then jump to Collections, then Reflection and Generics.
You should also know about jars, packaging applications and libraries, using an IDE, knowing some Ant/Maven.
I'd say that's the "required" Java SE "core" knowledge.