Java/C2/Non-static-block/English-timed

Time	Narration
00:02	Welcome to the Spoken Tutorial on Non-static block in java.
00:06	In this tutorial we will learn
00:08	About non-static block
00:10	When a non-static block executed?
00:13	Simple example of non-static block
00:16	And Why we need constructors?
00:18	Here we are using Ubuntu version 11.10 Java Development Environment jdk 1.6 And Eclipse IDE 3.7.0
00:26	To follow this tutorial you must know
00:29	How to create a constructor in Java using Eclipse
00:33	If not, for relevant tutorials please visit our website which is as shown, (http://www.spoken-tutorial.org)
00:38	Now we will see what a non-static block is.
00:42	Any code written between two curly brackets is a non-static block.
00:46	We can see the syntax here.
00:51	When is a non-static block executed ?
00:54	A non-static block is executedfor each object that is created.
00:58	It executes before the constructor's execution.
01:04	It can initialize instance member variables of the class.
01:08	Any other execution like calculation could also be given in the block.
01:14	Now, let us switch to Eclipse and try to use a non-static block.
01:22	I have already opened a class named NonStaticTest in Eclipse.
01:28	I also have a created a class named A .
01:33	Now inside class A , I will first create a variable of type int.
01:38	So type int a semicolon, then press Enter
01:46	Within curly brackets type System dot out dot println within brackets and double quotes Non static block of an instance of Class A semicolon.
02:12	Then type System dot out dot println within brackets and double quotes The value of a is plus a semicolon.
02:32	Now we will declare a constructor.
02:35	So type public A opening and closing brackets, open the curly brackets press Enter.
02:51	Then type System dot out dot println within brackets and double quotes Constructing object of type A semicolon.
03:10	Then type System dot out dot println within brackets and double quotes The value of a is plus a semicolon.
03:35	Now save this file.
03:44	Inside class NonStaticTest in Eclipse let us create an object of the class A.
03:53	So type A space a1 equal to new space A opening and closing brackets semicolon
04:08	Next line we will create one more object of class A.
04:12	So type A space a2 equal to new space A opening and closing brackets semicolon.
04:25	Now Save and run the file. So press Ctrl &S and Ctrl &F11 keys
04:32	We get the output as follows:
04:35	As we can see when the first object is created, the non-static block is executed.
04:45	non-static block of an instance of class A and the instance variable a is initialized to 0.
04:53	Only after that the constructor is executed. Constructing object of type A
05:02	And here the instance variable is again initialized to 0.
05:07	Then again when the second object is created, the non-static block is executed.
05:16	This process is repeated.
05:20	We can have multiple non-static blocks in a class.
05:25	In this case they execute in the sequence in which they appear in the class.
05:30	We can try that now.
05:34	Include one more block after the first one in class A.
05:43	So again type inside curly brackets.
05:47	System dot out dot println within brackets and double quotes Second Non static block of an instance of Class A semicolon.
06:08	Then type System dot out dot println within brackets and double quotes The value of a is plus a semicolon.
06:30	Now save this file ,press Ctrl & S key simultaneously then press Ctrl & F11 to run the program.
06:44	We get the output as follows.
06:48	we see that after the first block is executed, the second is executed.
06:58	Only then the constructor is executed.
07:07	Now you might feel why do we need constructors.
07:10	The answer is we don't need the default constructor.
07:15	But the non-static block cannot be parameterized.
07:18	You cannot have objects taking values from out side.
07:22	So non-static block is not a substitute for constructor.
07:27	So let us summarizes
07:29	In this tutorial we learnt :
07:32	About non-static block and how to use this block.
07:35	For self assessment,
07:36	create a class named B.
07:39	Create a non-static block and a constructor as shown in the tutorial.
07:44	Create an object of class B in the class NonStaticTest already created.
07:49	Check the output.
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08:37	Thus we have come to the end of this tutorial.
08:40	This is Arya Ratish from IIT BOmbay signing off. Thanks for joining.

Contributors and Content Editors

Arya Ratish, Devisenan, Gaurav, PoojaMoolya, Sandhya.np14, Sneha