In JDK5, Annotation is introduced. Annotation just simplify programming, not for performance raising

DD(deployment description) over Annotation

CoC, Convention over Configuration

DRY, Don't Repeat Yourself

heap size vs. GC

• big heap size : GC less frequent, slower(a lot of memory to search through)  
• small: GC more frequent, fast

ArrayList.toArray(new xxx[0]), 参数用零长度相应Java对象的数组即可。