How to avoid ConcurrentModificationException when iterating over a map and changing values?

Question

I\'ve got a map containing some keys (Strings) and values (POJOs)

I want to iterate through this map and alter some of the data in the POJO.

The current code

Answer 1

For such purposes you should use the collection views a map exposes:

• keySet() lets you iterate over keys. That won't help you, as keys are usually immutable.
• values() is what you need if you just want to access the map values. If they are mutable objects, you can change directly, no need to put them back into the map.
• entrySet() the most powerful version, lets you change an entry's value directly.

Example: convert the values of all keys that contain an upperscore to uppercase

for(Map.Entry entry:map.entrySet()){
    if(entry.getKey().contains("_"))
        entry.setValue(entry.getValue().toUpperCase());
}

Actually, if you just want to edit the value objects, do it using the values collection. I assume your map is of type :

for(Object o: map.values()){
    if(o instanceof MyBean){
        ((Mybean)o).doStuff();
    }
}