Java : Wrapper Class

The purpose of using Wrapper class instead of primitive types are

• Primitive types do not use new an object to create variables and have their own values.
• Because some Java APIs can only use objects (for example, Collection), not primitive types (ie, int, long, char, boolean, etc.) to handle the data.
  • ArrayList, HashMap, etc.can only be stored in objects
• In order to make these primitive types applicable to these APIs, Java use wrapper class to do it.

Process of Auto-boxing and unboxing

Integer obj = new Integer(123);

int num = obj.intValue();

Some examples

//autobox : Primitive to Wrapper Class
int num = 7;
Integer num1 = num;

// autounbox : Wrapper Class to Primitive
int num2 = num1;

// use class method to convert string to number
String str = "150";
int num3 = Integer.parseInt(str);
System.out.println(num3 * 12);
//1800

// Convert an Integer object to an int value
Integer i = 6;
int j = i.intValue();
System.out.println(j);
// 6