How to remove a key from HashMap while iterating over it

Question

I am having HashMap called testMap which contains String  String   HashMap lt String  String gt  testMap   new HashMap lt String  String gt       When iterating the map  if value is match with specified string  I need to remove the key from map   i e   for Map Entry lt String  String gt  entry   testMap entrySet        if entry getValue   equalsIgnoreCase  Sample          testMap remove entry getKey             testMap contains  Sample  but I am unable to remove the key from HashMap  Instead getting error     Exception in thread  main  java util ConcurrentModificationException     at java util HashMap HashIterator nextEntry Unknown Source      at java util HashMap EntryIterator next Unknown Source      at java util HashMap EntryIterator next Unknown Source

User · Answer

To remove specific key and element from hashmap use

hashmap.remove(key)

full source code is like

import java.util.HashMap;
public class RemoveMapping {
     public static void main(String a[]){
        HashMap hashMap = new HashMap();
        hashMap.put(1, "One");
        hashMap.put(2, "Two");
        hashMap.put(3, "Three");
        System.out.println("Original HashMap : "+hashMap);
        hashMap.remove(3);   
        System.out.println("Changed HashMap : "+hashMap);        
    }
}

Source : http://www.tutorialdata.com/examples/java/collection-framework/hashmap/remove-mapping-of-specified--key-from-hashmap

User · Answer

Try   Iterator lt Map Entry lt String String gt  gt  iter   testMap entrySet   iterator    while  iter hasNext          Map Entry lt String String gt  entry   iter next        if  Sample  equalsIgnoreCase entry getValue              iter remove              With Java 1 8 and onwards you can do the above in just one line   testMap entrySet   removeIf entry - gt   Sample  equalsIgnoreCase entry getValue

User · Answer

Use Iterator remove

[java] How to remove a key from HashMap while iterating over it?

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