int test = 0 ;
Vector testVec = new Vector();
testVec.add( new Integer( test )); // Converted primitive value to object.
int testInt = ((Integer)testVec.elementAt(0)).intValue(); // Again converted to primitive value from objects.
From J2SE 5.0 , life is somehow easy as in J2SE 5.0 it automatically converts primitive value to object and an object to again primitive value.
Converting primitive values like int, double, long etc to objects like Integer, Double and Long automatically called as autoboxing
Integer intObj = 7 // Auto boxing
Automatically converting wrapper types into their primitive equivalents is called as Auto Unboxing
int intvalue = New Integer( 7 );
These two are very helpful in assignments , doing constructor invocations or passing argument to a method.