//Defining a Student class.  
class Student{  
  
 /* Student attributes */
 String name;  
 int age;
 long mobileNo;
 int level;
 
 //default constructor
 public Student(){
   
 }
 
 //parametrized constructor
 public Student(String name, int age, long mobileNo, int level){
  /*
   * this.variable_name always refer to class level properties
   */
   //set object properties from the arguments/parameters
   this.name = name;
   this.age = age;
   this.mobileNo = mobileNo;
   this.level = level;
 }
 
 //accessor method to show the student details
 void displayStudent(){
   System.out.println("Name: "+this.name);
   System.out.println("Age: "+this.age);
   System.out.println("Mobile No: "+this.mobileNo);
   System.out.println("Level: "+this.level);
 }
 
 //mutator method to update the age of student by 2 years
 void updateAge(){
   this.age += 2;
 }
 
 //creating main method inside the Student class  
 public static void main(String args[]){  
   
  //Creating an object or instance  
  Student s1=new Student("Alex",21,1234567891,10);//creating an s1 object of Student  
  Student s2=new Student("Bob",37,1987654321,11);//creating an s2 object of Student  

  //Call updateAge() method
  s1.updateAge();
  s2.updateAge();
  
  //Call displayStudent() method
  s1.displayStudent();
  s2.displayStudent();
 }  
}
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