Boxing and unboxing

To make use of the wrapper classes, we need to have means to convert a value of a primitive data type (such as int) to an ``equivalent'' value of the corresponding wrapper class (called boxing), and vice-versa (called unboxing).

• Boxing is done by creating an object of the corresponding wrapper class passing the primitive type value as an argument to the wrapper class constructor.

  Example:

  Integer anIntegerObject = new Integer(25);
  Double aDoubleObject = new Double(3.6);
  Character aCharacterObject = new Character('A');
  

  The variable anIntegerObject now references an object of the class Integer that corresponds to the int value 25. Similarly, for the variables aDoubleObject and aCharacterObject.

• Unboxing is done by invoking specific methods of the wrapper classes (called accessor methods), that return the primitive data type value corresponding to an object of a wrapper class. The names of an accessor method is always primitivetypeValue(), and it returns a value of primitivetype.

  Example:

  int i = anIntegerObject.intValue();
  double d = aDoubleObject.doubleValue();
  char c = aCharacterObject.charValue();
  

  The variable i now contains the value 25, the variable d the value 3.6, and the variable c the value 'A'.