Concurrent Modification Exception in HashMap

Question

I'm writing this program in Java and I'm getting a java.util.ConcurrentModificationException. The code excerpt is given below, please let me know if more code is required.

for (String eachChar : charsDict.keySet()) {
    if (charsDict.get(eachChar) < 2) {
        charsDict.remove(eachChar);
    }
}

charsDict is defined as

Map<String, Integer> charsDict = new HashMap<String, Integer>();

Please help me :)

Answer 1

You're not allowed to remove elements from the map while using its iterator.

A typical solution to overcome this:

List<String> toBeDeleted = new ArrayList<String>();
for (String eachChar : charsDict.keySet()) {
    if (charsDict.get(eachChar) < 2) {
        toBeDeleted.add(eachChar);
    }
}

for (String eachChar : toBeDeleted) {
    charsDict.remove(eachChar);
}