TYPES, VALUES, AND VARIABLES

Variables Have Types, Objects Have Classes

4.5.5

The local variable

c

 has as its type the interface type

Colorable

, so it can

hold a reference to any object whose class implements

Colorable

; specifi 

cally, it can hold a reference to a

ColoredPoint

.

Note that an expression such as  

new Colorable()

  is not valid because it is

not possible to create an instance of an interface, only of a class.

Every array also has a class; the method

getClass

 ( 20.1.1), when invoked

for an array object, will return a class object (of class

Class

) that represents the

class of the array. The classes for arrays have strange names that are not valid Java

identifiers; for example, the class for an array of

int

 components has the name

[I

  and so the value of the expression:

new int[10].getClass().getName()

is the string

"[I"

; see  20.1.1 for details.

Oft on the dappled turf at ease

I sit, and play with similes,

Loose types of things through all degrees.

 William Wordsworth,

To the Same Flower

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