¿Se puede eliminar de HashMap?

Can you remove from HashMap?

HashMap. remove() is an inbuilt method of HashMap class and is used to remove the mapping of any particular key from the map. It basically removes the values for any particular key in the Map. Parameters: The method takes one parameter key whose mapping is to be removed from the Map.

There is a numerous number of ways to iterate over HashMap of which 5 are listed as below: Iterate through a HashMap EntrySet using Iterators. Iterate through HashMap KeySet using Iterator.

While iterating, check for the key at that iteration to be equal to the key specified. The entry key of the Map can be obtained with the help of entry. getKey() method. If the key matches, remove the entry of that iteration from the HashMap using remove() method.

How to delete an entry from a HashMap during Iteration

1. Get a Set of keys or Set of entries by calling keySet() or entrySet() method of java.util.Map.
2. Get the Iterator from the key set or entry set.
3. Iterate over key set or entry set.
4. Check each value, if it satisfies criterion call iterator.remove() method.

We need to iterate through the bucket and its index one by one and comparing the hashValue and key of each Entry object. In line 7 , If condition is true then we get the desired Entry object which we need to remove from the hashmap object .

Well, you can’t do it by iterating over the set of values in the Map (as you are doing now), because if you do that then you have no reference to the keys, and if you have no reference to the keys, then you can’t update the entries in the map, because you have no way of finding out which key was associated with the …

keyset () method of HashMap returns a set of keys in the HashMap and its backed by HashMap i.e. any items removed from the Key Set will be removed from HashMap too. So lets Iterate over the HashMap using KeySet Iterator and remove all the elements whose value is ODD, while Iterating i.e.

keyset() method of HashMap returns a set of keys in the HashMap and its backed by HashMap i.e. any items removed from the Key Set will be removed from HashMap too. So lets Iterate over the HashMap using KeySet Iterator and remove all the elements whose value is ODD, while Iterating i.e.

While iterating, check for the key at that iteration to be equal to the key specified. The entry key of the Map can be obtained with the help of entry.getKey () method. If the key matches, remove the entry of that iteration from the HashMap using remove () method.

Either you iterate on the keys, or on the entries. // there is no iterator for Maps, but there are methods to do this.

If 2 different threads perform operations on same HashMap object simultaneously/concurrently, then JVM throws ConcurrentModificationException Q) How ConcurrentModificationException can be handled ?

But if we make modifications in hashmap like given below, then it will not throw any such exception as the size of the hashmap won’t change. This example works completely fine as while the iterator is iterating over the map, the size of the map is not changing. Only the map is being updated in the if statement.

Note that the fail-fast behavior of an iterator cannot be guaranteed as it is, generally speaking, impossible to make any hard guarantees in the presence of unsynchronized concurrent modification. Fail-fast iterators throw ConcurrentModificationException on a best-effort basis.

The Java library calls an attempt to modify a Collection while iterating through it a “concurrent modification”, which unfortunately suggests the only possible cause is simultaneous modification by multiple threads, but that is not so.