Instance variable Vs Local variables

Instance variable Vs Local variable

Instance variables are defined in the class.
When local variable name is same as instance variable.
Then local variable hides instance variable.
See the following example:

class student {
    
	// followings are instance variables
        String name; 
		int rollno;
		String address;
		// In the following method, names of local variables (i.e. arguments in the method) are same as names of instance variables
		// In this case, when we try to access variables, then local variables will be accessed, instance variables can not be accessed.
		// Because local variables hide instance variables of the same name.
        public void setdata (String name, int rollno, String address)
        {
			
			
        }
}

Here local variables (name, rollno and address) have same name as instance variales names.
To resolve above problem, use this keyword.
Because, this keyword always has access to current object. (i.e. it will access the instance variables of the current object)
See the following example:

class student {
    
	// followings are instance variables
        String name; 
        int rollno;
		String address;
		
        public void setdata (String name, int rollno, String address)
        {
			// following is use of  this  keyword
			this.name = name;
			this.rollno = rollno;
			this.address = address;
			
        }
}

In the above program, this.name refers the instance variable (i.e.class variable) of the class student.
And name without this keyword, is local variable of the method setdata().
Similarly, this.rollno and this.address are instance variables of the class student.
And rollno and address without this keyword, are local variables of the method setdata().

Now see the full program:

public class student {
    
	// followings are instance variables
        String name; 
        int rollno;
		String address;
		
        public void setdata (String name, int rollno, String address)
        {
			// following is use of  this  keyword
			this.name = name;
			this.rollno = rollno;
			this.address = address;
			
        }
		public void dispdata(){
			// here, no need to use this keyword
			// because same name local variables are not present
		    System.out.println("Name is " + name);
			System.out.println("Rollno is "+ rollno);
			System.out.println("Address is "+address);
		}	
		
	public static void main(String args[])	{
            student s1 = new student();
            s1.setdata("Gargi",170067,"New Delhi");
            s1.dispdata();
            			   
	}
}

Output

Name is Gargi
Rollno is 170067
Address is New Delhi

Remember: Local variables hides Instance variables in the method.

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