Difference between revisions of "Instantiation"
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* '''CANNOT call an instance method or access instance variables till the super constructor has run.''' | * '''CANNOT call an instance method or access instance variables till the super constructor has run.''' | ||
* Only Static variables can be accessed as a call to super() or this(). | * Only Static variables can be accessed as a call to super() or this(). | ||
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| + | == Field Initializers == | ||
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| + | * Initialization of fields can be specified in field declaration statements. | ||
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== Initialization Blocks == | == Initialization Blocks == | ||
Revision as of 09:31, 16 August 2011
Constructors
- Every class - including Abstract classes - MUST have a constructor.
- Constructor chaining is built in. Every class constructor will call its default superclass constructor using super().
- Every constructor as its first statement has a call to this() or super().
- Compiler will only automatically insert call to no-arg super() or this().
- CANNOT call an instance method or access instance variables till the super constructor has run.
- Only Static variables can be accessed as a call to super() or this().
Field Initializers
- Initialization of fields can be specified in field declaration statements.
Initialization Blocks
- A static initialization block runs when the class is first loaded.(Runs only once)
- An instance init block runs every time a new instance is created.
- An instance init block runs right after the call to super() in a constructor (ie. after all the super-constructors have run).
- In case of multiple init blocks (either instance and static) they run in the order in which they are defined.
