Java/C2/Constructor-overloading/English-timed

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: Ubuntu version 11.10 OS Java Development kit 1.6 Eclipse 3.7.0
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. http://www.spoken-tutorial.org
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.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.
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09:43	This brings us to the end of the tutorial.
09:46	Thanks for joining.This is Prathamesh Salunke, signing off. Jai Hind.

Contributors and Content Editors

Devisenan, Gaurav, PoojaMoolya, Sandhya.np14, Sneha