HashMap and other Collection types are frequently used in Java application programming. This post will explain why exception would be thrown when deleting element with Map.remove() while looping through a Map using Iterator. This issue would also occur to other Collection types such as Set, List.Below is a sample code snippet demonstrating the exception thrown.Map<String,String> map = Collections.synchronizedMap(new TreeMap<String,String>()); map.put("key1","value1");map.put("key2","value2");map.put("key3","value3"); Set<Entry<String,String>> entries = map.entrySet(); I...