Java Reference
In-Depth Information
java -cp logging.jar;. PackageInfo logging 1.0 logging.File
This time, you should see the following output:
Name: logging
Implementation title: Logging Implementation
Implementation vendor: Jeff Friesen
Implementation version: 1.0a
Specification title: Logging Specification
Specification vendor: Jeff Friesen
Specification version: 1.0
Sealed: true
Compatible with 1.0: true
Primitive Type Wrapper Class
The java.lang packageincludes Boolean , Byte , Character , Double , Float ,
Integer , Long , and Short . These classes are known as primitive type wrapper
classes because their instances wrap themselves around values of primitive types.
Note The primitive type wrapper classes are also known as value classes .
Java provides these eight primitive type wrapper classes for two reasons:
• The Collections Framework (discussed in Chapter 5 ) provides lists, sets, and
in the collection.
• These classes provide a good place to associate useful constants (such as
MAX_VALUE and MIN_VALUE ) and class methods (such as Integer 's
parseInt() methodsand Character 's isDigit() , isLetter() ,and
toUpperCase() methods) with the primitive types.
This section introduces you to each of these primitive type wrapper classes and a
java.lang class named Number .
Boolean isthesmallestoftheprimitivetypewrapperclasses.Thisclassdeclaresthree
constants, including TRUE and FALSE , which denote precreated Boolean objects. It
also declares a pair of constructors for initializing a Boolean object:
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