Java: Wrapper Classes

Wrapper classes provide a way to use primitive data types (int, boolean, etc..) as objects.

Sometimes you must use wrapper classes, for example when working with Collection objects, such as ArrayList, where primitive types cannot be used:

 For example, the following methods are used to get the value associated with the corresponding wrapper object: intValue(), byteValue(), shortValue(), longValue(), floatValue(), doubleValue(), charValue(), booleanValue().

public class Main {
  public static void main(String[] args) {
    Integer myInt = 5; -> Integer
    Double myDouble = 5.99; -> Double
    Character myChar = 'A'; -> Character
    System.out.println(myInt.intValue()); -> int
    System.out.println(myDouble.doubleValue()); -> double
    System.out.println(myChar.charValue()); -> char
  }
}

public class Main {
  public static void main(String[] args) {
    Integer myInt = 100;
    String myString = myInt.toString();
    System.out.println(myString.length());
  }
}
// Outputs: 3