Static Methods, Factory Methods

• Just like static fields, static methods belong to the class, not its objects.
• Thus, you do not need to declare an object to use the method.
• This is inherently more efficient, because objects take up space in memory.
• If the method does not access object-specific fields, or when it only accesses static fields, it can (and should) be declared static.
• Example: String strNumber = Integer.parseInt(intNumber); converts the int intNumber to a String, strNumber, via the Integer class.  But notice that you do not need to instantiate an Integer object to use it.
• For the Java Foundation Classes, you can tell static methods because they say so.
• Remember our discussion about Factory Methods?
• A factory method is a static method that returns an instance of an object.
• This means that the constructor is called internally, by that method, and the constructor is usually marked private.
• Thus, you cannot get an object by NumberFormat percent = new NumberFormat(), you must get it by NumberFormat percent = NumberFormat.getPercentInstance();
• Why?  What are the advantages?
• What is a static method we have been using all along in this class?  What is its purpose?


 Method Parameters

Created by:  Brandan Jones January 4, 2002