Static & Static Factory Methods

Static belong to class NOT to the instance (object)

Static Variable: gets memory only once in the class area at the Time of Loading

Static Methods : Invoked without creating instance (eg. Math.pow())

• useful for memory management
• Static can be blocks, variables, methods & nested class (inner class)

can access static data member

Inheritance : Static methods of only parent is visible

Static method Restrictions

• Cannot use non-static data field or method directly
• Cannot use this and super on the static context

Static Initialization Blocks

What is Static Factory Method?

When a static method returns the same Class Object (reference type) of its own class, its called Static Factory Method

example

Runtime r = Runtime.getRuntime();

JAVA 9 Enhancement; of() method is static factory method

// shortcut way to create UNMODIFIABLE Collection Object (no add or remove works after it)
List<Integer> l = List.of(2, 3, 4, 5, 6, 7);//upto 10 elements, post which var-arg method
// but using var arg is costly

Optional<List<String>> strOptional = Optional.of(Arrays.asList("John","Doe"));
List<String> stringList = strOptional.get();