Skim chapters 1-3 and 5-6 of Core Java for the Impatient.

Alternatively, you can renew your programming skills using this java text: How to Think Like a Computer Scientist

In particular, read about

• Variables and Assignment
• Methods (from Adding new methods to Methods with multiple parameters) and return values
• Loops (Particularly the first two sections on multiple assignment and the while statement.)
• Arrays

Carefully read the following chapters

• Strings and things (also Operators for Strings)
• Mutable objects
• Create your own objects
• Arrays
• Arrays of objects