Description Maxime Daniel 2005-11-02 11:20:35 EST

Explicit constructor calls upon primitive types wrappers (Boolean, Byte,
Character, Short, Integer, Long, Float and Double) have significant drawbacks
compared to the use of a factory method (such as Boolean.valueOf()) or a boxing
conversion (in 5.0 mode). Especially, the valueOf reference documentation
insists that it is expected to have better space and time behavior than the
constructor, and JLS 5.1.7 requires that some values be treated as singletons by
conforming implementations (true, false, bytes, chars between \u0000 and \u007f
inclusive, ints and shorts between -128 and 127 inclusive). Their use could
raise a specific warning (note that boxing conversions already raise a warning
as of 3.2 M2).

In support for this, the following code:
class X {
  public static void main(String args[]) {
	  Integer i1 = new Integer(0),
	  i2 = (Integer) 0,
	  i3 = Integer.valueOf(0);
	  if (i1 == i2) {
		  System.out.println("i1 == i2");
	  }
	  if (i1 == i3) {
		  System.out.println("i1 == i3");
	  }
	  if (i3 == i2) {
		  System.out.println("i2 == i3");
	  }
  }
}

(only) displays:
i2 == i3