class Student{

int rollno;

String name;

String city;

Student(int rollno, String name, String city){

this.rollno=rollno;

this.name=name;

this.city=city;

}

public String toString(){

//overriding the toString() method else printing object give its memory location

return rollno+" "+name+" "+city;

}

public static void main(String args[]){

Student s1=new Student(101,"Raj","lucknow");

Student s2=new Student(102,"Vijay","ghaziabad");

System.out.println(s1);//compiler writes here s1.toString()

System.out.println(s2);//compiler writes here s2.toString()

/*

* use of string buffer , which makes string mutable , they are thread-safe

*/

StringBuffer sb=new StringBuffer("Hello ");

sb.append("Java");//now original string is changed

System.out.println(sb);//prints Hello Java

}

}