Give an example of code using static and finalize
Example Code: using static & finalize ()
We want to count exact number of objects in memory of a Student class the one defined earlier. For this purpose, we will modify Student class.
Add a static variable countStudents which helps in maintaining the count of student objects.
Write a getter for this static variable. (Remember, getter also should be static one. Hoping so, you know the grounds).
In all constructors, write a code which will increment countStudents by one.
Override finalize() method and decrement countStudents variable by one.
Override toString() method.
Class Object is a superclass (base or parent) class of all the classes in java by default. It has already finalize() and toString() method (used to convert an object state into string). Thus we are actually overriding these methods over here.
By making all above modifications, student class will look like
// File Student.java
public class Student {
private String name;
private int rollNo;
private static int countStudents = 0;
// Standard Setters
public void setName (String name) {
this.name = name;
}
// Note the masking of class level variable rollNo
public void setRollNo (int rollNo) {
if (rollNo > 0) {
this.rollNo = rollNo;
}else {
this.rollNo = 100;
}
}
// Standard Getters
public String getName ( ) {
return name;
}
public int getRollNo ( ) {
return rollNo;
}
// gettter of static countStudents variable
public static int getCountStudents(){
return countStudents;
}
// Default Constructor public Student() {
name = "not set";
rollNo = 100;
countStudents += 1;
}
// parameterized Constructor for a new student
public Student(String name, int rollNo) {
setName(name); //call to setter of name
setRollNo(rollNo); //call to setter of rollNo
countStudents += 1;
}
// Copy Constructor for a new student
public Student(Student s) {
name = s.name;
rollNo = s.rollNo;
countStudents += 1;
}
// method used to display method on console
public void print () {
System.out.print("Student name: " +name);
System.out.println(", roll no: " +rollNo);
}
// overriding toString method of java.lang.Object class
public String toString(){
return "name: " + name + " RollNo: " + rollNo;
}
// overriding finalize method of Object class
public void finalize(){
countStudents -= 1;
}
} // end of class