Fourth of July week learning experience

In this week's study, we made a total of seven hours code, learning the switch can only support byte, short, char, int these basic data types and their corresponding package types. Brackets behind the switch can only put an int, but the byte, short, char type, they are automatically converted to an int (small fine precision conversion to large), they are also supported. A deeper understanding of the use of a switch statement, using the common method of Object: clone getclass method and so on. Java four references, the strength of soft imaginary scene used. According to reference intensity from strong to weak successively into: strong references, soft references (the SoftReference), weak reference (WeakReference), dangling reference (the PhantomReference) in four.