Wrapper Classes in Java

  1. They convert primitive data types into objects. Objects are needed if we wish to modify the arguments passed into a method (because primitive types are passed by value).
  2. The classes in java.util package handles only objects and hence wrapper classes help in this case also.
  3. Data structures in the Collection framework, such as ArrayList and Vector, store only objects (reference types) and not primitive types.
  4. An object is needed to support synchronization in multithreading.
// Java program to demonstrate Autoboxingimport java.util.ArrayList; 
class Autoboxing
{
public static void main(String[] args)
{
char ch = 'a';
// Autoboxing- primitive to Character object conversion
Character a = ch;
ArrayList<Integer> arrayList = new ArrayList<Integer>();// Autoboxing because ArrayList stores only objects
arrayList.add(25);
// printing the values from object
System.out.println(arrayList.get(0));
}
}
25
// Java program to demonstrate Unboxing 
import java.util.ArrayList;
class Unboxing
{
public static void main(String[] args)
{
Character ch = 'a';
// unboxing - Character object to primitive conversion
char a = ch;
ArrayList<Integer> arrayList = new ArrayList<Integer>();
arrayList.add(24);
// unboxing because get method returns an Integer object
int num = arrayList.get(0);
// printing the values from primitive data types
System.out.println(num);
}
}
24
// Java program to demonstrate Wrapping and UnWrapping 
// in Java Classes
class WrappingUnwrapping
{
public static void main(String args[])
{
// byte data type
byte a = 1;
// wrapping around Byte object
Byte byteobj = new Byte(a);
// int data type
int b = 10;
//wrapping around Integer object
Integer intobj = new Integer(b);
// float data type
float c = 18.6f;
// wrapping around Float object
Float floatobj = new Float(c);
// double data type
double d = 250.5;
// Wrapping around Double object
Double doubleobj = new Double(d);
// char data type
char e='a';
// wrapping around Character object
Character charobj=e;
// printing the values from objects
System.out.println("Values of Wrapper objects (printing as objects)");
System.out.println("Byte object byteobj: " + byteobj);
System.out.println("Integer object intobj: " + intobj);
System.out.println("Float object floatobj: " + floatobj);
System.out.println("Double object doubleobj: " + doubleobj);
System.out.println("Character object charobj: " + charobj);
// objects to data types (retrieving data types from objects)
// unwrapping objects to primitive data types
byte bv = byteobj;
int iv = intobj;
float fv = floatobj;
double dv = doubleobj;
char cv = charobj;
// printing the values from data types
System.out.println("Unwrapped values (printing as data types)");
System.out.println("byte value, bv: " + bv);
System.out.println("int value, iv: " + iv);
System.out.println("float value, fv: " + fv);
System.out.println("double value, dv: " + dv);
System.out.println("char value, cv: " + cv);
}
}
Values of Wrapper objects (printing as objects)
Byte object byteobj: 1
Integer object intobj: 10
Float object floatobj: 18.6
Double object doubleobj: 250.5
Character object charobj: a
Unwrapped values (printing as data types)
byte value, bv: 1
int value, iv: 10
float value, fv: 18.6
double value, dv: 250.5
char value, cv: a

--

--

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store