Error in Converting a Map to ConcurrentMap in Java

user_4056736 0
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I have a Map<String,Object> to be converted to a ConcurrentMap<String,Object>

    Map<String,Object> testMap = new HashMap<String,Object>();
    testMap.put("test", null); //This null causing issues in conversion
    testMap.put("test2","123");
    testMap.put("test3",234);
    ConcurrentMap<String,Object> concMap = new ConcurrentHashMap<>(testMap);

I get a null pointer exception. If I copy to a new HashMap<String,Object>

    Map<String,Object> testMap = new HashMap<String,Object>();
    testMap.put("test", null);
    testMap.put("test2","123");
    testMap.put("test3",234);
    Map<String,Object> concMap = new HashMap<>(testMap);

I don't get any errors. Is there a safe way to a Map<String,Object> to a ConcurrentMap<String,Object> without the NullPointerException

java.util.concurrent java
3 Answers
user_28377410

If you look into the source code of ConcurrentHashMap you will see, it doesn't allow null key or value - 

java.util.concurrent.ConcurrentHashMap#putVal

/** Implementation for put and putIfAbsent */
final V putVal(K key, V value, boolean onlyIfAbsent) {
    if (key == null || value == null) throw new NullPointerException();
user_30290170

The issue is not about converting a HashMap into ConcurrentHashMap. It is more about ConcurrentHashMap being null-safe, it does not allow null values. From its documentation:

Like Hashtable but unlike HashMap, this class does not allow null to be used as a key or value.

user_24112430
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