Multiple If conditions using Iterator in Java

Question

I have a list which has elements 1 through 10. I try to remove the prime numbers 2,3,5,7 from it and then print the rest of the list using iterator.But this code throws a NoSuchElementException. this is my code :

public static void editerate2(Collection<Integer> list3)
{
    Iterator<Integer> it=list3.iterator();
    while(it.hasNext())
    {
        if(it.next()==2 || it.next()==3 || it.next() ==5 || it.next()==7 ) 
        {
            it.remove();
        }
    }
    System.out.println("List 3:");
    System.out.println("After removing prime numbers  : " + list3);
}

What's the correct way of doing this? Also what's the difference between using "|" and "||" ???

As for the difference between | and ||, that's a topic for another question- although if you're particularly curious, a google search for "Bitwise Operator" may help you out. — username tbd
– username tbd, Commented Dec 12, 2012 at 2:32

jahroy · Accepted Answer · 2012-12-14 04:55:15Z

6

Each time you call it.next() your iterator advances to the next element.

This is NOT what you want to do I assume.

You should do this in stead:

Iterator<Integer> it = list.iterator();

while (it.hasNext()) {
    Integer thisInt = it.next();
    if (thisInt == 2 || thisInt == 3 || thisInt == 5 || thisInt == 7) {
       it.remove();
    }
}

The difference between | and ||:

If you use || and the first part is true, then the 2nd part will not be evaluated.

If you use | both parts will always be evaluated.

This is handy for cases like this:

if (person == null || person.getName() == null) {
    // do something
}

The above snippet would throw a NullPointerException if you used | and person was null.

That's because it would evaluate both parts of the condition, and the second half would de-reference a null object.

edited Dec 14, 2012 at 4:55

answered Dec 12, 2012 at 2:30

jahroy

22.8k10 gold badges63 silver badges111 bronze badges

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

Comments

Makoto · Accepted Answer · 2012-12-12 02:33:53Z

1

You want to avoid multiple calls to your iterator, as that advances it to the next element.

What you can do is preserve the value you get per iteration, then do your comparisons.

while(it.hasNext()) {
    Integer next = it.next();
    if(next == 2 || next == 3 || next == 5 || next == 7 ) {
        it.remove();
    }
}

answered Dec 12, 2012 at 2:33

Makoto

107k29 gold badges199 silver badges236 bronze badges

Collectives™ on Stack Overflow

Multiple If conditions using Iterator in Java

2 Answers 2

The difference between | and ||:

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

The difference between | and ||:

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related