How do I remove values found in one ArrayList from another ArrayList?

Question

I have two ArrayLists

ArrayList<Integer> values = new ArrayList<Integer>();
values.add(9);

That's one, here's the other:

ArrayList<Integer> values2 = new ArrayList<Integer>();
for(int j = 1; j < 10; j++){
        values2.add(j);
    }

How can I compare the two and remove 9 from the second ArrayList? I tried using a foreach statement but I kept getting

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 9, Size: 1
at java.util.ArrayList.rangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)

This had been a head-peck for some hours now and I appreciate any help you can offer

Dawood ibn Kareem · Accepted Answer · 2013-10-30 02:50:28Z

8

You use

values2.removeAll(values);

From the Javadoc for the Collection interface (http://docs.oracle.com/javase/7/docs/api/java/util/Collection.html) -

boolean removeAll(Collection c)

Removes all of this collection's elements that are also contained in the specified collection (optional operation). After this call returns, this collection will contain no elements in common with the specified collection.

answered Oct 30, 2013 at 2:50

Dawood ibn Kareem

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2 Comments

MattKnowles Over a year ago

Gonna slam my head against a brick wall now, thanks bro. My profile picture is so relevant right now.

Dennis Meng Over a year ago

@MattKnowles Happens to the best of us. As long as the docs are your first source, you'll be fine in the long run.

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