Wrapper classes in Java are : Integer,Character,Boolean,Float,Double,Long,Short and Byte.
Don’t get confused in between Wrapper class and primitive data types ,remember in Wrapper class , Every wrapper class name start with CAPITAL letter for example : Boolean , here B is capital.
The process of converting primitive data type into Objects is called Wrapping
To declare an integer “rollNumber” holding the value 20, we can write as : int rollNumber=20;
The object representation of integer “rollNumber” holding value 20 will be :
Integer integerObject =new Integer(rollNumber);
Here , class Integer is the wrapper class wrapping a primitive data type rollNumber
The process of converting the object into primitive type is called as Unwrapping.
int rollNumber= integerObject.intValue();
The Integer Class :
Integer class is a wrapper for values of type int.
Integer objects can be constructed with int value , or string containing an int value.
The Constructors of Integer :
Integer(int num)
Integer(String str) throws NumberFormatException
some methods of the Integer class :
static int parseInt(String val) throws NumberFormatException
int intValue() return the value of the invoking object as an int value.
The Character class :
Character class is a wrapper for char data types.
Constructor of Character class :
Character(char a) : here a specifies the character to be wrapped by the Character object
once character object is created you can retrieve primitive character value from it using :
char charValue()
The Boolean Class
The Boolean class is a wrapper class for boolean type values.
It has following Constructors :
Boolean(boolean value) : here value can be either true or false.
Boolean(String str): here , str can be “true” or “false” , it can be upper case or lower case.
The Float class
Float class is a wrapper class for floating point values of type float.
Float objects can be constructed with a float value,or a String containing floating point value.
The constructor of Float class are :
Float(float num)
Float(String value) throws NumberFormatException
some methods of Float class :
static Float valueOf(String val) throws NumberFormatException
float floatValue() return the value of invoking object as a float value.
The Double Class
Class Double is a wrapper class for floating-point values of type double.
Double class object can be constructed with a double value, or a string containing a floating-point value.
The constructors for double are shown here :
Double(double num)
Double(String val) throws NumberFormatException
some methods of Double class :
static Double valueOf(String str) throws NumberFormatException
double doubleValue() return the value of invoking object as a double value.
The Long Class
Class Long is a wrapper class for values of type long.
Long class object can be constructed with a long value, or a string containing a long type value.
The constructors for Long are shown here :
Long(long num)
Long(String val) throws NumberFormatException
some methods of Long class :
static Long valueOf(String str) throws NumberFormatException
long longValue() return the value of invoking object as a long value.
The Short Class
Class Short is a wrapper class for values of type short.
Short class object can be constructed with a short value, or a string containing a short type value.
The constructors for Short are shown here :
Short(short num)
Short(String val) throws NumberFormatException
some methods of Short class :
static Short valueOf(String str) throws NumberFormatException
Short shortValue() return the value of invoking object as a short value.
The Byte Class
Class Byte is a wrapper class for values of type byte.
Byte class object can be constructed with a byte value, or a string containing a long type value.
The constructors for Byte are shown here :
Byte(byte num)
Byte(String val) throws NumberFormatException
some methods of Byte class :
static Byte valueOf(String str) throws NumberFormatException
Byte byteValue() return the value of invoking object as a Byte value.