Difference between revisions of "Java/C2/Methods/English-timed"

|00:02

| Welcome to the Spoken Tutorial on '''methods''' in  java.

|In this tutorial, we will learn:

|To create a '''method'''.   

|And to '''call''' a '''method'''.  

|00:13

|Here we are using,'''Ubuntu version 11.10'''

|'''Java Development kit 1.6''' and

 

|'''Eclipse 3.7.0'''

| 00:24

| To follow this tutorial, you must know how to write, compile and run a simple java program in '''eclipse'''.

|If not, for relevant tutorials, please visit our website which is as shown.

http://www.spoken-tutorial.org  

|A java '''method''' is a collection of statements that performs a specified operation.

|00:46

|Let us now write a '''method'''.

|So, in the '''eclipse,''' I have already created a project '''Methods'''.

|00:57

|In the project, I have created a java class named '''MethodDemo'''.

|01:06

|In the '''class''', outside the '''main method''', we will write a '''method'''.

|So, type: '''void''' name of the '''method'''

|Let us name it as '''displayMessage''' parentheses '''Enter'''.

|And curly brackets.

|01:32

|A '''method''' can  return a value.

|But if you don’t want the method to return a value then the keyword '''void''' is used.

|01:42

|Alright, now inside the curly brackets, let us print a message.

|So, type: '''System '''dot''' out '''dot '''println Hello Method'''.  

|02:06

|So, we have written a '''method'''.

|Now, we will '''call''' this '''method'''.

|So, inside the  '''main''' method,  we will  create an object of the '''class''' '''MethodDemo'''.

|So, '''MethodDemo''' object name.

|Let's name it as '''md =new ''' '''MethodDemo''' parentheses semicolon.  

|02:37

|So, we have created an object '''md''' of the class '''MethodDemo''' using the '''new''' operator.

|02:48

| Now, let us call the method '''displayMessage.'''

| 02:51

| So, type: '''md''' dot '''displayMessage();'''.  

|03:00

|The 'dot' operator is used to '''call''' the '''method'''.

| 03:06

| Now, let us '''Run''' this application by clicking on '''Run''' icon.

| We see the output '''Hello Method '''on the '''console'''.

|Now, let us return an '''integer ''' instead of '''void'''.

| So, type: '''int'''.

|Also, make the method '''public''', that is accessible everywhere.

|By default, it is '''private''', that is accessible only within the class where it is written.

|03:45   

|Now, inside the method, type '''return''' seven semicolon.

|03:55

|Remember that we write  the '''return'''  statement  at the end of all statements in the '''method'''.

|This is because after '''return''' statement no other statements are executed.

|04:08

|Now, inside the '''main''' method, at the end, type the 'print' statement.

|So, type: '''System''' dot '''out''' dot '''println();'''

|04:23

|Within parentheses, we will '''call''' the '''method'''.

|So, put '''md''' dot '''method''' inside the parentheses, remove the semicolon.

|This will print the '''return''' value of the method.

|04:42

|'''Run''' the application.

|04:45  

|We see in the output, the value '''7''' is printed.

|04:51

|Now we will write another method and call this method in '''displayMessage.'''

| So, type: '''public void ''' method name '''square ''' within parentheses '''int a'''.

|05:15

|Here, we are giving '''int a''' as a parameter to our method.

| 05:20

| Now, within curly brackets type: '''System '''dot '''out '''dot '''println''' within parentheses '''a''' into '''a'''.

| So, we have written a '''square''' method

| that will display a square of an integer which is  given as a parameter.

|05:48

|Let us call this method in the '''displayMessage''' method.  

| So, type: '''square''' within parentheses an integer '''5''' semicolon.

| 06:07

| '''Run''' this application.

|We see that the output displays the square of '''5''' that is '''25.'''

|Now, let us understand the flow of the application.

|The starting point is the '''main''' '''method'''.

|06:29

|In the '''Main '''method''', '''we have first called the '''displayMessage'''.

|06:34

|So, the control goes to the '''displayMessage'''

|and all the statements in the '''displayMessage''' are executed.  

|The first one is the '''print''' statement.

|06:50

|Then it comes across the '''square''' method.

|06:54

| So the control jumps to the '''square''' method.  

| The square method takes an '''integer 5''' and returns the square of the integer i.e. '''25'''.

| Then the control goes back to the '''displayMessage'''.

| 07:10

| Then the control jumps back to the '''main'''  function.

| Since there are no statements left to execute, in the '''main''' method, the application terminates.

| 07:29

| Alright! Now let us  make '''displayMessage''' as '''static'''.

| So, after '''public''' type '''static.'''

| We see that we cannot call a 'non static' method inside the '''static'''  method.

| 07:47

| So, we will '''comment''' this '''call'''.

| Since '''main''' is a static method, we can call the '''static  displayMessage '''inside this.

|08:02

| Now, for '''static method''', we do not need to create  an  object.

| So, we will '''comment''' this object creation.

| 08:11

| Also  we will delete '''md.'''

|08:18   

|'''Run''' the application.

|We see the output '''Hello Method '''and '''7'''.

|We do not see  25 because we have commented the call to '''square''' method.

|08:34  

|We can also call '''method''' from other '''class'''.

|For that, I have created a class '''Demo.'''

|08:45

|Inside the '''class''', create a '''method'''.

|So, type: '''public void show''' parentheses '''Enter'''.

|Inside curly brackets, '''System '''dot''' out '''dot''' println'''

| '''I am from other class.'''

| Go back to '''MethodDemo''' class.

| Now we will '''call''' this '''show''' method, inside the method '''MethodDemo''' class.

| For that we need to create the object of the class '''Demo.'''

|09:32

|This is because the  '''show'''  method belongs to the class '''Demo.'''

| So, type: '''Demo d=new Demo''' parentheses semicolon.

|09:48

|Then call the method '''show'''.

| 09:54

| Lets '''Run''' this application.

| We see on the console: '''I am from other class'''.

|  This is how '''methods''' are used in java.

|  The '''method''' name and the parameters form the signature of the '''method'''

| while the curly brackets and the statements form the body of the '''method'''.  

| So, in this tutorial, we have learnt:

|To create a '''method'''

 

|To call a '''method'''

 

|And different signatures of '''methods'''.

| For self assessment, create a '''method''' which prints the cube of an integer.

| 10:38

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|watch the video available at http://spoken-tutorial.org/What_is_a_Spoken_Tutorial.  

 

|It  summarizes the Spoken Tutorial project.

|If you do not have good bandwidth, you can download and watch it.

|10:54

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|11:08  

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|11:27

|We have come to the end of this tutorial.

|Thanks for joining.This is Prathamesh Salunke, signing off.