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Constructor-3


Constructor can be used for initializing instance variable of class.

Example1:-

class Student
{
private String name;
private int rollNo;
Student()
{
name="Rudraksha";
rollNo=101;
}
void disp()
{
System.out.println("Name is "+name);
System.out.println("RollNo is "+rollNo);
}
public static void main(String[]args)
{
Student s1=new Student();
s1.disp();
}
}

Output:-

C:\JAVATECH>javac Student.java
C:\JAVATECH>java Student

Name is Rudraksha
RollNo is 101


Example2:-

class Student
{
private String name;
private int rollNo;
Student(String n)
{
name=n;
}
Student(String n,int r)
{
name=n;
rollNo=r;
}
void disp()
{
System.out.println("Name is "+name);
System.out.println("RollNo is "+rollNo);
}

public static void main(String[]args)
{
Student s1=new Student("Rudraksha");
Student s2=new Student("Rudraksha",101);
s1.disp();
s2.disp();
}
}

Output:-

C:\JAVATECH>javac Student.java
C:\JAVATECH>java Student

Name is Rudraksha
RollNo is 0
Name is Rudraksha
RollNo is 101

Example3:-instance variable and local variable having same name

 class Student
{
private String name;
private int rollNo;

Student(String name,int rollNo)
{
name=name;
rollNo=rollNo;
}
void disp()
{
System.out.println("Name is "+name);
System.out.println("RollNo is "+rollNo);
}

public static void main(String[]args)
{
Student s1=new Student("Rudraksha",101);
s1.disp();

}
}

Output:-

C:\JAVATECH>javac Student.java
C:\JAVATECH>java Student

Name is null
RollNo is 0

Example4:-instance variable and local variable having same name than use this keyword for differentiate.

 class Student
{
private String name;
private int rollNo;

Student(String name,int rollNo)
{
this.name=name;
this.rollNo=rollNo;
}
void disp()
{
System.out.println("Name is "+name);
System.out.println("RollNo is "+rollNo);
}
public static void main(String[]args)
{
Student s1=new Student("Rudraksha",101);
s1.disp();

}
}

Output:-

C:\JAVATECH>javac Student.java
C:\JAVATECH>java Student

Name is Rudraksha
RollNo is 101

Here this keyword represent current object of class.



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