A Boxing conversion converts the values of a primitive type to the corresponding values of the reference type, for instance, from {{int}} to the type {{Integer}} \[[JLS 5.1.7 Boxing Conversion|http://java.sun.com/docs/books/jls/third_edition/html/conversions.html#5.1.7]\].  It can be convenient in many cases where an object parameter is desired, such as with collection classes like {{Map}} and {{List}}. Another use case is to pass object references to methods, as opposed to primitive types that are always passed by value. The resulting wrapper types also help reduce clutter in code.

Autoboxing can automatically wrap the primitive type to the corresponding wrapper object. Some care should be taken during this process, especially when performing comparisons. The Java Language Specification \[[JLS 05|AA. Java References#JLS 05]\] explains this point clearly:

This noncompliant code snippet \[[Techtalk 07|AA. Java References#Techtalk 07]\] prints {{100}} as the size of the {{HashSet}} while it is expected to print {{1}}. The combination of a {{short}} and an  {{integer}} value in the operation {{i-1}} leads to autoboxing into an {{Integer}} object. The {{HashSet}} contains only {{short}} values whereas (distinctly typed) {{Integer}} objects are being removed successively. The remove operation is as a result equivalent to a _No Operation_ (NOP). The compiler enforces type checking so that only {{short}} values are inserted, however, a programmer is free to remove an object of any type without triggering any exceptions since {{Collections<E>.remove}} takes an Object parameter and not {{E}}. Such behavior can result in unintended object retention or memory leaks.

public class ShortSet {
  public static void main(String[] args) {
    HashSet<Short> s = new HashSet<Short>();
      for(short i=0; i<100;i++) {
        s.add(i);
        s.remove(i - 1);
      }
    System.out.println(s.size());
  }
}

public class ShortSet {
  public static void main(String[] args) {
    HashSet<Short> s = new HashSet<Short>();
      for(short i=0; i<100;i++) {
        s.add(i);
        s.remove((short)(i-1));  //cast to short 
      }
    System.out.println(s.size());
  }
}

\[[Core Java 04|AA. Java References#Core Java 04]\] Chapter 5 
\[[JLS 05|AA. Java References#JLS 05]\] Section 5.1.7
\[[Techtalk 07|AA. Java References#Techtalk 07]\] "The Joy of Sets"