Title: Java: Wrapper Classes Post by: Admin on January 01, 2007, 02:17:29 AM Decription on going to and from the java Object wrapper classes.
Wrapper classes to exactly what they say, they wrap primitive types (eg: int, double, etc) in Objects which can be placed into Vectors, and many, many other uses. *Notice that an Object starts with a capital letter, while the primitives all start with a lowercase. Also notice that Strings are Ojects. These Wrapper classes can be created in many ways, so i will start slow, simply returning objects with a String. Integer from String: Integer i = Integer.valueOf("125"); Double from String: Double d = Double.valueOf("5.829754097"); Float from String: Float f = Float.valueOf("8.43543"); Boolean from String: Boolen b = Boolean.valueOf("true"); //This will represent true Character from String: Character c = Character.valueOf("G"); The more common use is given the primitive in a variable. This next section shows how to convert a variable to these wrapper classes and back to a primitive. Integer: int i = 5; Integer I = Integer.valueOf(i); //Wrapper int i2 = I.intValue(); //back to primitive Float: float f = 5.5f; Float F = Float.valueOf(f); //Wrapper float f2 = F.floatValue(); //back to primitive Double: double d = 5.55555; Double D = Double.valueOf(d); //Wrapper double d2 = D.doubleValue(); //back to primitive Boolean: boolean b = true; Boolean B = Boolean.valueOf(b); //Wrapper boolean b2 = B.booleanValue(); //back to primitive *When dealing with strings you may also wish to use the following to get primitives from the Object String: Integer: int i = Integer.parseInt("234"); Double double d = Double.parseDouble("234.6576533254"); Float: float f = Float.parseFloat("234.78"); Long: long l = Long.parseLong("23454654"); *Note you may wish to add the ().trim feature to these last ones, in the case of extra white space around your String, which may cause exceptions. Example of trim: String s = " William "; // displays as ' William ' String s2 = (s).trim(); //displays 'William' |