Wrapper class in java [closed]

Answer 1

As you are aware, In Java not everything is an Object. There are primitive types such as int ,double float etc. So if you wanted to use a primitive type in place of Object i.e. if a method expects an Object but you need to send in a primitive type, without Wrapper classes this wouldn't be possible. Take for instance the Map interface. The put(Object,Object) method takes Objects as both key and value. If you, for example wanted to store a mapping between an integer value 1 (int i=1) to an Object, without wrapper classes this wouldn't be possible. Wrapper classes are used to represent primitive values when an object is required.

Answer 2

The general idea of a wrapper class is a class that, for lack of a better term, 'boxes' another class or some other functionality. This could be done to abstract the wrapped items, and expose a simpler interface to the user.

I think your specific question concerns the Java Primitive Wrapper Classes, which are classes that represent the primitive types (int, double, boolean, byte, and so on) as classes. One of the reasons for this is they are used for when Object types are needed and you want to use primitives, like when using any class in java.Collections.

Answer 3

According to what Wikipedia says to my question "What is a wrapper class in Java":

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.