Difference between revisions of "Java/C2/Constructor-overloading/English-timed"
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Revision as of 14:52, 8 April 2015
| Time | Narration |
| 00:03 | Welcome to the Spoken Tutorial on constructor overloading in java. |
| 00:08 | In this tutorial, we will learn |
| 00:10 | what is constructor overloading |
| 00:13 | and to overload constructor. |
| 00:16 | Here we are using:
|
| 00:27 | To follow this tutorial, you must know |
| 00:30 | how to create constructors in java using eclipse. |
| 00:34 | If not, for relevant tutorials, please visit our website which is as shown. |
| 00:40 | What is constructor overloading? |
| 00:43 | Define multiple constructors for a class. |
| 00:46 | They must differ in number or types of parameters. |
| 00:50 | Let us now see how to overload constructor. |
| 00:54 | In eclipse, I have a class Student with two variables and a method. |
| 01:03 | Let us first create a parameterized constructor. |
| 01:07 | So, type: Student within parentheses int number comma String the_name. |
| 01:26 | Within curly brackets, type: roll_number is equal to number. |
| 01:38 | And name is equal to the_name |
| 01:46 | So, we have a constructor with two parameters. |
| 01:51 | Let us call this constructor. |
| 01:53 | So, in main method type: new Student parentheses semicolon. |
| 02:03 | We see an error, it states that constructor Student is undefined. |
| 02:10 | This is simply because we have defined a constructor with two parameters. |
| 02:16 | And we are calling a constructor without parameters. |
| 02:22 | So, we need to pass arguments. |
| 02:25 | So, within parentheses type: 22 comma in double quotes Ram. |
| 02:33 | We see that the error is resolved. |
| 02:36 | Let us call the method. |
| 02:38 | So, before new , type: Student s is equal to new student. |
| 02:45 | Now, using the object s we will call the method studentDetail(). |
| 02:53 | Save the program and Run. |
| 02:58 | We see the output: 22 and Ram. |
| 03:03 | Now let us define a constructor with no parameter. |
| 03:07 | So, type: Student parentheses. |
| 03:12 | Within curly brackets roll_number is equal to 0. |
| 03:21 | And name is equal to in double quotes hyphen that is no name. |
| 03:30 | So, now we can call the constructor with no parameters. |
| 03:35 | So, type: Student s1 is equal to new Student parentheses semicolon. |
| 03:47 | This time we see no error, since we have defined a constructor without parameter. |
| 03:55 | Then s1 dot studentDetail();. |
| 04:01 | Save and Run the program. |
| 04:04 | So, in the output we see zero and dash when the default constructor is called. |
| 04:11 | This is constructor overloading. |
| 04:13 | We have two constructors with different parameters. |
| 04:17 | Both the constructors obviously have same name. |
| 04:20 | So, depending on the type and number of parameters, the constructor is called. |
| 04:26 | Let us see the advantage of constructor overloading. |
| 04:30 | Suppose, now we call a constructor with two parameters. |
| 04:35 | So, type: Student s3= new Student(); |
| 04:51 | Now within parentheses, suppose I gave the name argument first and then the roll_number. |
| 04:58 | Let's see what happens. |
| 04:59 | So, in double quotes Raju comma 45. |
| 05:08 | We see an error which states that "The constructor Student with the parameter String comma int is undefined." |
| 05:18 | So, let us first define the constructor. |
| 05:22 | So, type: Student within parentheses String the_name comma int r_no. |
| 05:42 | So, over here first parameter is string and the second parameter is int. |
| 05:52 | Then, within curly bracket, roll_number is equal to r_no; |
| 06:05 | and name is equal to the_name; |
| 06:15 | Save the program. |
| 06:18 | Now we see that the error is resolved. |
| 06:22 | Let us call the method. |
| 06:24 | So, s3 dot studentDetail(); |
| 06:29 | Save the program and Run. |
| 06:35 | So, we see the output 45 and Raju. |
| 06:40 | So, here we see that when we call the constructor |
| 06:43 | we do not have to worry about the parameters that we are passing. |
| 06:47 | This is simply because we have defined multiple constructors with different parameters. |
| 06:54 | So, the proper constructor is overloaded. |
| 06:57 | We can therefore now define a constructor which takes only one parameter. |
| 07:02 | That is roll number. |
| 07:05 | So, type: Student within parentheses int num, |
| 07:16 | within curly brackets roll_number is equal to num. |
| 07:25 | And name is equal to "no name". |
| 07:33 | Now, let us call this constructor. |
| 07:43 | So, type: Student s4 is equal to new Student;. This time we will pass a single argument. So, let us pass 61. |
| 08:04 | Then s4 dot studentDetail(); |
| 08:10 | Save and Run the program. |
| 08:14 | So, in the output we see the roll number as 61 and name as no name. |
| 08:21 | As we can see, the proper overloaded constructor is called when new is executed. |
| 08:27 | Based upon the parameters specified, the proper constructor is overloaded. |
| 08:33 | This is how constructor overloading is done. |
| 08:40 | So, in this tutorial, we have learnt: |
| 08:42 | * About the constructor overloading |
| 08:45 | * To overload constructor and the use of constructor overloading |
| 08:50 | For self assessment, create multiple constructors for class Employee and overload the constructor. |
| 08:58 | To know more about the Spoken Tutorial project, |
| 09:00 | watch the video available at [1]. |
| 09:06 | It summarizes the Spoken Tutorial project. |
| 09:09 | If you do not have good bandwidth, you can download and watch it. |
| 09:12 | The Spoken Tutorial project team: |
| 09:15 | Conducts workshops using spoken tutorials. |
| 09:17 | Gives certificates to those who pass an online test. |
| 09:20 | For more details, please write to contact@spoken-tutorial.org |
| 09:26 | Spoken Tutorial Project is a part of the Talk to a Teacher project. |
| 09:30 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 09:35 | More information on this mission is available at
[2]. |
| 09:43 | This brings us to the end of the tutorial. |
| 09:46 | Thanks for joining. |
| 09:47 | This is Prathamesh Salunke, signing off. Jai Hind. |
