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Primitive wrapper class 255
Primitive wrapper class
A primitive wrapper class in the Java programming language is one of eight classes provided in the java.lang
package to provide object methods for the eight primitive types. All of the primitive wrapper classes in Java are
immutable. J2SE 5.0 introduced autoboxing of primitive types into their wrapper object, and automatic unboxing of
the wrapper objects into their primitive value—the implicit conversion between the wrapper objects and primitive
values.
Wrapper classes are used to represent primitive values when an Object is required. The wrapper classes are used
extensively with Collection classes in the java.util package and with the classes in the java.lang.reflect reflection
package.
The primitive wrapper classes and their corresponding primitive types are:
Primitive type Wrapper class Constructor
Arguments
byte Byte byte or String
short Short short or String
int Integer int or String
long Long long or String
float Float float, double or String
double Double double or String
char Character char
boolean Boolean boolean or String
The Byte, Short, Integer, Long, Float, and Double wrapper classes are all subclasses of the Number class.
Void
Although it is not a wrapper class, the Void class is similar in that it provides an object representation of the void
return type. The Void class is an uninstantiable placeholder class used by the java.lang.reflect API to hold a
reference to the Class object representing the Java keyword void..
Atomic wrapper classes
With Java 5.0, additional wrapper classes were introduced in the java.util.concurrent.atomic package. These classes
are mutable and cannot be used as a replacement for the regular wrapper classes. Instead, they provide atomic
operations for addition, increment and assignment.
The atomic wrapper classes and their corresponding types are: