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)
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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;
}
}
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