Constructor in java
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CONSTRUCTOR S.G.V.P.Gunasekara - 2015238 1 s . g . v . p . b . g u n a s e k a r a - 2 0 1 5 2 3 8 - w 1 6 0 8 4 6 2
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Transcript of Constructor in java
s.g.v.p.b.gunasekara - 2015238 - w1608462
1
CONSTRUCTORS.G.V.P.Gunasekara - 2015238
s.g.v.p.b.gunasekara - 2015238 - w1608462
2Constructor
Constructor in java is a special type of method that is used to initialize the object.
Java constructor is invoked at the time of object creation. It constructs the values i.e. provides data for the object that is why it is known as constructor.
s.g.v.p.b.gunasekara - 2015238 - w1608462
3Rules for creating java constructor
There are basically two rules defined for the constructor.
1. Constructor name must be same as its class name
2. Constructor must have no explicit return type
s.g.v.p.b.gunasekara - 2015238 - w1608462
4Types of java constructors
There are two types of constructors:
1. Default constructor (no-arg constructor)
2. Parameterized constructor
s.g.v.p.b.gunasekara - 2015238 - w1608462
5Default constructor
A constructor that have no parameter is known as default constructor. Syntax of default constructor:
<class_name>(){} Example of default constructor
In this example, we are creating the no-arg constructor in the Bike class. It will be invoked at the time of object creation.
class Bike1{ Bike1(){
System.out.println("Bike is created");}
public static void main(String args[]){ Bike1 b=new Bike1();
} }
s.g.v.p.b.gunasekara - 2015238 - w1608462
6Parameterized constructor
A constructor that have parameters is known as parameterized constructor.
Why use parameterized constructor?
Parameterized constructor is used to provide different values to the distinct objects.
s.g.v.p.b.gunasekara - 2015238 - w1608462
7 Example of parameterized constructor
In this example, we have created the constructor of Student class that have two parameters. We can have any number of parameters in the constructor.
class Student4{ int id; String name; Student4(int i,String n){
id = i; name = n; } void display(){System.out.println(id+" "+name);} public static void main(String args[]){ Student4 s1 = new Student4(111,"Karan"); Student4 s2 = new Student4(222,"Aryan"); s1.display(); s2.display(); }
}
s.g.v.p.b.gunasekara - 2015238 - w1608462
8Output:
111 Karan 222 Aryan
s.g.v.p.b.gunasekara - 2015238 - w1608462
9Constructor overloading
Like other methods in java constructor can be overloaded i.e. we can create as many constructors in our class as desired. Number of constructors depends on the information about attributes of an object we have while creating objects.
s.g.v.p.b.gunasekara - 2015238 - w1608462
10example: constructor overloading example:class Language {
String name;
Language() {
System.out.println("Constructor method called.");
}
Language(String t) {
name = t;
}
public static void main(String[] args) {
Language cpp = new Language();
Language java = new Language("Java");
cpp.setName("C++");
java.getName();
cpp.getName();
}
void setName(String t) {
name = t;
}
void getName() {
System.out.println("Language name: " + name);
}
}
s.g.v.p.b.gunasekara - 2015238 - w1608462
11Output:
Constructor method called. Language name: java Language name:c++
s.g.v.p.b.gunasekara - 2015238 - w1608462
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