Remove item from HashMap, Java Question?

Question

Hi, I want to remove an item from the HashMap by applying criteria. Consider this code:

    Set set = myMap.keySet();
    Iterator itr = set.iterator();
    while (itr.hasNext())
    {
        Object o = itr.next();
        if (o.toString().length() < 3) {
            myMap.remove(o.toString()); //remove the pair if key length is less then 3
    }

So, I get the ConcurentModification Exception runtime because during the iteration I modify the HashMap. What should I do? Are there any other ways to search my criteria and run the remove command at the end so that I can avoid this exception?

Answer 1

Use itr.remove()insteadmyMap.remove(o.toString())

Answer 2

As with Java 8, Collection provides removeIf(Predicate<? super E>)that will remove all elements for which the given predicate returns true. The example in the question can be rewritten as

myMap.keySet().removeIf(o -> o.toString().length() < 3);

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Answer 3

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Answer 4

- itr.remove()

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Answer 5

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Map<String,Object> map = // obtained somehow;

Map<String,Object> filtered = Maps.filterKeys(map, new Predicate() {
    @Override
    public boolean apply(String input) {
        return input.length() < 3;
    }
});

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