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How to sort a vector elements that contains the user define
class object? (Note: If Suppose consider, A Student class
contain two data members. They are String studentName and
int rollNo. I am creating Four objects for this class, each
object contains students details like name and roll no. Now
i am storing that objects in vector and if i retiving the
elements from the vector means then it should be display in
sorting order)

Answer Posted / naren reddy

For sorting Any user defined class,We need to implement the
userdefined class with comparable or comparator
interfcae.Then only your collections.sort(ArrayList al)
will work,Otherwise it won't work.


Ex: class Employee implements Comparable{

private int age;

public void setAge(int age){
this.age=age;
}

public int getAge(){
return this.age;
}public int compareTo(Object otherEmployee){

/*
If passed object is of type other than Employee,
throw ClassCastException.
*/

if(!(otherEmployee instanceof Employee)){
throw new ClassCastException("Invalid object");
}

int age = ((Employee) otherEmployee).getAge();

if(this.getAge() > age)
return 1;
else if ( this.getAge() < age )
return -1;
else
return 0;

}

}

Is This Answer Correct ?    2 Yes 0 No



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