Wrapper Classes

Java wrapper classes serve following primary purposes:

• Provide a way to "wrap" primitive values in an object so that the primitive types can also be used in activities reserved for objects, like being added to Collections. Note: With Java 5's addition of auto-boxing (and unboxing), many of the wrapping operations are now handled automatically that needed to be done manually.
• Provide utility functions for primitives, like conversion functions (converting primitives to and from String objects, and converting primitives and String objects to and from different bases, such as binary, octal, and hexadecimal).

Below table defined the Wrapper classes for primitive types with their constructors:

Primitive	Wrapper Class	Constructor Arguments
boolean	Boolean	boolean or String
byte	Byte	byte or String
double	Double	double or String
float	Float	float, double, or String
int	Integer	int or String
long	Long	long or String
short	Short	short or String

Any constructor that accepts String as an argument throws NumberFormatException.

Example:
Integer
       Integer int1 = new Integer(11);
       Integer int2 = new Integer("11");

Float
       Float float1 = new Float(1.45f);
       Float float2 = new Float("1.45f");

Character
Accepts only char as constructor argument.
       Character c1 = new Character('j');

Boolean
The constructors for the Boolean wrapper take either a boolean (true or false), or a String. For a String, “true” (case insensitive) will be considered as true, everything else will result in false. Java 5 onwards, Boolean can also be used in conditional statements.

       Boolean b1 = new Boolean(true);

       Boolean b2 = new Boolean("true");

       if (b1) // works only Java 5 onwards

Java 5 has also added new feature of auto-boxing. You can read full article here.