Java Reference
In-Depth Information
Summary
Java's standard class library provides various language-oriented APIs via the
java.lang
and
java.math
packages. These APIs include
Math
and
StrictMath
,
Package
, Primitive Type Wrapper Class, Reference, Reflection,
String
,
StringBuffer
and
StringBuilder
,
System
, Threading,
BigDecimal
, and
BigInteger
.
The
Math
and
StrictMath
classes offer a wide variety of useful math-oriented
methods for calculating trigonometric values, generating pseudorandom numbers, and
soon.
StrictMath
differsfrom
Math
byensuringthatallofthesemathematicalop-
erations yield the same results on all platforms.
The
Package
class provides access to package information. This information in-
cludesversiondetailsabouttheimplementationandspecificationofaJavapackage,the
package's name, and an indication of whether the package is sealed or not.
Instances of the
Boolean
,
Byte
,
Character
,
Double
,
Float
,
Integer
,
Long
, and
Short
primitive type wrapper classes wrap themselves around values of
primitive types. These classes are useful for storing primitive values in collections,
and for providing a good place to associate useful constants (such as
MAX_VALUE
and
MIN_VALUE
)andclassmethods(suchas
Integer
's
parseInt()
methodsand
Character
's
isDigit()
,
isLetter()
, and
toUpperCase()
methods) with
the primitive types.
The Reference API makes it possible for an application to interact with the garbage
collector in limited ways. This API consists of classes
Reference
,
Referen-
ceQueue
,
SoftReference
,
WeakReference
, and
PhantomReference
.
SoftReference
is useful for implementing image caches,
WeakReference
is
usefulforpreventingmemoryleaksrelatedtohashmaps,and
PhantomReference
is
usefulforlearningwhenanobjecthasbeenfinalizedsothatitsresourcescanbecleaned
up.
TheReflectionAPIletsapplicationslearnaboutloadedclasses,interfaces,enums(a
kind of class), and annotation types (a kind of interface). It also lets applications load
classes dynamically, instantiate them, find a class's fields and methods, access fields,
call methods, and perform other tasks reflectively.
TheentrypointintotheReflectionAPIisaspecialclassnamed
Class
.Additional
classes include
Constructor
,
Field
,
Method
,
AccessibleObject
, and
Ar-
ray
.
