Difference between revisions of "Java/C2/Non-static-block/English-timed"

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Revision as of 15:11, 22 August 2014

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.


07:51 To know more about the Spoken Tutorial Project
07:53 Watch the video available at http://spoken-tutorial.org/What_is_a_Spoken_Tutorial
07:56 It summarizes the Spoken Tutorial project
08:00 If you do not have good bandwidth, you can download and watch it


08:03 The Spoken Tutorial Project Team
08:06 Conducts workshops using spoken tutorials
08:08 Gives certificates for those who pass an online test
08:12 For more details, please write to contact@spoken-tutorial.org


08:18 Spoken Tutorial Project is a part of the Talk to a Teacher project
08:22 It is supported by the National Mission on Education through ICT, MHRD, Government of India
08:28 More information on this Mission is available at


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