Removing element from ArrayList through Iterator

Question

I want to make a look up for entry in ArrayList and remove element if it's found, the simplest way I guess is through Iterator, here's my code:

    for (Iterator<Student> it = school.iterator(); it.hasNext();){
        if (it.equals(studentToCompare)){
            it.remove();
            return true;
        }
        System.out.println(it.toString());
        it.next();
    }

But something is wrong: instead of iterating through my ArrayList<Student> school I get using it.toString():

java.util.ArrayList$Itr@188e490
java.util.ArrayList$Itr@188e490
...

What's wrong?

You are doing a toString() of the iterator, not of Student — SJuan76
– SJuan76, Commented Jun 15, 2013 at 11:56
ArrayList$Itr@188e490 is the address of the iterator itself. — Maroun
– Maroun, Commented Jun 15, 2013 at 11:57

johnchen902 · Accepted Answer · 2013-06-15 11:56:49Z

22

it is a Iterator, not Student

for (Iterator<Student> it = school.iterator(); it.hasNext();){
    Student student = it.next();
    if (student.equals(studentToCompare)){
        it.remove();
        return true;
    }
    System.out.println(student.toString());
}

answered Jun 15, 2013 at 11:56

johnchen902

9,6191 gold badge29 silver badges70 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Suresh Atta · Accepted Answer · 2013-06-15 12:08:23Z

14

Why not ?

school.remove(studentToCompare);

Use List remove(Object) method.

Removes the first occurrence of the specified element from this list, if it is present (optional operation).

And moreover

It Returns true if this list contained the specified element (or equivalently, if this list changed as a result of the call).

edited Jun 15, 2013 at 12:08

answered Jun 15, 2013 at 11:58

Suresh Atta

122k38 gold badges206 silver badges315 bronze badges

2 Comments

fge Over a year ago

Could highlight the fact that it both returns true on success, AND that it removes the first element; both having the cake and eating it given OP's question

Tapas Adhikary Over a year ago

Your answer is the preferred one. But the iterator will be useful when you are looping through the list and based on some condition you would like to remove an element from the list being inside the loop.

T-Bull · Accepted Answer · 2013-06-15 12:02:44Z

1

for (Iterator<Student> it = school.iterator(); it.hasNext();){
    **Student st** = it.next();
    if (**st**.equals(studentToCompare)){
        it.remove();
        return true;
    }
    System.out.println(**st**.toString());
}

OR

school.remove(school.indexOf(studentToCompare));

OR

school.remove(studentToCompare);

The latter two examples assume school is a List.

answered Jun 15, 2013 at 12:02

T-Bull

2,1462 gold badges15 silver badges20 bronze badges

Comments

Prasad Kharkar · Accepted Answer · 2013-06-15 12:06:18Z

1

The reason you are getting this output is because you are calling toString() method on iterator and not on the Student object.

You can remove student from the list by using

school.remove(student);

Also, if you want to print meaningful Student object information when you write

System.out.println(student);

Override toString() method for it as System.out.println() statement would internally call toString() on student object.

public String toString() {
    return "Student [id=" + id + ", firstName=" + firstName
            + ", lastName=" + lastName + "]";
}

edited Jun 15, 2013 at 12:06

answered Jun 15, 2013 at 11:58

Prasad Kharkar

13.6k5 gold badges42 silver badges57 bronze badges

Collectives™ on Stack Overflow

Removing element from ArrayList through Iterator

4 Answers 4

Comments

2 Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

2 Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related