Java constructors
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The document explains Java constructors, which are special methods used for object initialization and have the same name as the class, detailing the two types: default (no-arg) and parameterized constructors. It highlights the differences between constructors and methods, such as return types and invocation methods. Additionally, it mentions constructor overloading and outlines various training topics and courses offered by Quontra Solutions.
![Default Constructors
Example for default constructor:
class Cons{
cons(){
System.out.println("constructor is created");
}
public static void main(String args[]){
Cons c=new Cons();
}
}
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![Parameterized Constructors
Example for parameterized 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(); }
}
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Java constructors
- 1. Call : (404) 900-9988, (404) 990-3007, Mail Us: [email protected] Quontra Solutions by Java Constructors
- 2. Constructor • 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 • They do not contain any return type • Constructor name is same as class name Call : (404) 900-9988, (404) 990-3007, Mail Us: [email protected]
- 3. Types of Constructors • Default constructor (no-arg constructor) • Parameterized constructor Types of constructors Default constructor Parameterized constructor Call : (404) 900-9988, (404) 990-3007, Mail Us: [email protected]
- 4. Default Constructors Example for default constructor: class Cons{ cons(){ System.out.println("constructor is created"); } public static void main(String args[]){ Cons c=new Cons(); } } Call : (404) 900-9988, (404) 990-3007, Mail Us: [email protected]
- 5. Parameterized Constructors Example for parameterized 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(); } } Call : (404) 900-9988, (404) 990-3007, Mail Us: [email protected]
- 6. Difference between constructor and method Constructor Method Constructor is used to initialize the state of an object. Method is used to expose behaviour of an object. Constructor must not have return type Method must have return type. Constructor is invoked implicitly. Method is invoked explicitly. Constructor name must be same as the class name. Method name should not be same as class name Call : (404) 900-9988, (404) 990-3007, Mail Us: [email protected]
- 7. Constructor Overloading • Constructors are methods that can be overloaded, just like any other method in a class. • Constructors having the same name with different parameter list is called constructor overloading. Call : (404) 900-9988, (404) 990-3007, Mail Us: [email protected]
- 8. Topics Covered during Training • Classes, Objects, Keywords, Methods • Exception Handling • String Handling • Multithearding • AWT • Swing • Applet • Collections • Hibernate • Struts etc……………… Call : (404) 900-9988, (404) 990-3007, Mail Us: [email protected]
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