How to resolve the "java.util.concurrentmodificationexception"
The java.util.concurrentmodificationexception is an error in Java. The error occurs when the iterator is traversing a list, and a command is used to change an element’s value during that traversal.
Code
The following example gives an error because the list is printed using an iterator, and the value “3” is being removed. These instructions can not be executed in this order. Therefore, they must be executed separately.
import java.util.ArrayList;import java.util.HashMap;import java.util.Iterator;import java.util.List;import java.util.Map;class ConcurrentModificationExceptionExample {public static void main(String args[]) {List<String> myList = new ArrayList<String>();myList.add("1");myList.add("2");myList.add("3");myList.add("4");myList.add("5");Iterator<String> it = myList.iterator();while (it.hasNext()) {String value = it.next();System.out.println("List Value:" + value);if (value.equals("3"))myList.remove(value); //this line gives// error}}}
When the following line is commented, the code runs perfectly.
if (value.equals("3"))
myList.remove(value);
However, what if the user needs to remove the value equal to three from the list? Then, printing and removal will be done separately.
Code
The following code correctly removes the value equal to 3 and prints the list.
import java.util.ArrayList;import java.util.HashMap;import java.util.Iterator;import java.util.List;import java.util.Map;class ConcurrentModificationExceptionExample {public static void main(String args[]) {List<String> myList = new ArrayList<String>();myList.add("1");myList.add("2");myList.add("3");myList.add("4");myList.add("5");myList.remove("3"); //This removes the elementIterator<String> it = myList.iterator();while (it.hasNext()) {String value = it.next();System.out.println("List Value:" + value);}}}
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