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Numeric wrapper classes are very similar to each other. Each contains the methods doubleValue() , floatValue() , intValue() , longValue() , shortValue() , andbyteValue() . These methods convert objects into primitive type values.

The wrapper classes do not have no-arg constructors. The instances of all wrapper classes are immutable; this means that, once the objects are created, their internal values cannot be changed.

The abstract class Number defines a superclass that is implemented by the classes that wrap the numeric types byte, short, int, long, float, and double. Number has abstract methods that return the value of the object in each of the different number formats. For example, doubleValue( ) returns the value as a double, floatValue( ) returns the value as a float, and so on.

xxxValue () method

The method converts the value of the Number Object that invokes the method to the primitive data type that is returned from the method. The wrapper classes provide constructors, constants, and conversion methods for manipulating various data types.

xxxValue () method is used to convert an object to the valuexxx Number data type and return.

Here is a separate method for each primitive data type ?

byte byteValue()
short shortValue()
int intValue()
long longValue()
float floatValue()
double doubleValue()

Related methods and it's Description:

Types of	Method and Description
byte	byteValue (): Returns a byte value.
abstract double	doubleValue (): In double Returns the specified value.
abstract float	floatValue (): Returns a float value.
abstract int	intValue (): Returns as int the specified value.
abstract long	longValue (): In long form returns the specified value.
short	shortValue (): In short form returns the specified value.

Parameters

Here is the detail of parameters ?

• All these are default methods and accepts no parameter. The wrapper classes do not have no-arg constructors

Return Value

• These methods convert objects into primitive type values. This method returns the primitive data type that is given in the signature. The values returned by these methods can be rounded

 

Number has six concrete subclasses that hold explicit values of each numeric type: Double, Float, Byte, Short, Integer, and Long.

Most wrapper class names for a primitive type are the same as the primitive data type name with the first letter capitalized. The exceptions are Integer and Character

Example:

Program:

public class ValueMethod {

   public static void main(String args[]) {
      Integer x = 12;

      // Returns byte primitive data type
      System.out.println( x.byteValue() );

      // Returns double primitive data type
      System.out.println(x.doubleValue());

      // Returns long primitive data type
      System.out.println( x.longValue() );
   }
}

Output:

12
12.0
12
Press any key to continue . . .

The wrapper classes provide constructors, constants, and conversion methods for manipulating various data types.

java.lang.Integer

 -value: int

+MAX_VALUE: int

+MIN_VALUE: int

+Integer(value: int)

+Integer(s: String)

+byteValue(): byte

+shortValue(): short

+intValue(): int

+longVlaue(): long

+floatValue(): float

+doubleValue(): double

+compareTo(o: Integer): int

+toString(): String

+valueOf(s: String): Integer

+valueOf(s: String, radix: int): Integer

+parseInt(s: String): int

+parseInt(s: String, radix: int): int 

The wrapper classes provide constructors, constants, and conversion methods for manipulating various data types.

java.lang.Double

-value: double 

+MAX_VALUE: double 

+MIN_VALUE: double 

+Double(value: double) 

+Double(s: String) 

+byteValue(): byte 

+shortValue(): short 

+intValue(): int 

+longVlaue(): long 

+floatValue(): float 

+doubleValue(): double 

+compareTo(o: Double): int 

+toString(): String 

+valueOf(s: String): Double 

+valueOf(s: String, radix: int): Double 

+parseDouble(s: String): double 

+parseDouble(s: String, radix: int): double 

Each numeric wrapper class has the constants MAX_VALUE and MIN_VALUE . MAX_VALUE represents the maximum value of the corresponding primitive data type. For Byte , Short , Integer , and Long , MIN_VALUE represents the minimum byte , short , int , and long val- ues. For Float and Double , MIN_VALUE represents the minimum positive float and double values. The following statements display the maximum integer (2,147,483,647), the minimum positive float (1.4E–45), and the maximum double floating-point number (1.79769313486231570e+308d).

System.out.println("The maximum integer is " + Integer.MAX_VALUE);
System.out.println("The minimum positive float is " +Float.MIN_VALUE);
System.out.println("The maximum double-precision floating-point number is " +Double.MAX_VALUE);

Float and Double define the following constants:

Serial	wrapper the constants	Description
1	MAX_EXPONENT	Maximum exponent (Added by Java SE 6.)
2	MAX_VALUE	Maximum positive value
3	MIN_EXPONENT	Minimum exponent (Added by Java SE 6.)
4	MIN_NORMAL	Minimum positive normal value (Added by Java SE 6.)
5	MIN_VALUE	Minimum positive value
6	NaN	Not a number
7	POSITIVE_INFINITY	Positive infinity
6	NEGATIVE_INFINITY	Negative infinity
9	SIZE	The bit width of the wrapped value
10	TYPE	The Class object for float or double

Number instance methods :

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