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Difference between ArrayList and CopyOnWriteArrayList in Java
Following are the notable differences between ArrayList and CopyOnWriteArrayList classes in Java.
| ArrayList | CopyOnWriteArrayList | |
|---|---|---|
| Synchronized | ArrayList is not synchronized. | CopyOnWriteArrayList is synchronized. |
| Thread Safe | ArrayList is not thread safe. | CopyOnWriteArrayList is thread safe. |
| Iterator type | ArrayList iterator is fail-fast and ArrayList throws ConcurrentModificationException if concurrent modification happens during iteration. | CopyOnWriteArrayList is fail-safe and it will never throw ConcurrentModificationException during iteration. The reason behind the it that CopyOnWriteArrayList creates a new arraylist every time it is modified. |
| Remove Opearation | ArrayList iterator supports removal of element during iteration. | CopyOnWriteArrayList.remove() method throws exception if elements are tried to be removed during iteration. |
| Performance | ArrayList is faster. | CopyOnWriteArrayList is slower than ArrayList. |
| Since Java Version | 1.2 | 1.5 |
Example
import java.util.Iterator;
import java.util.concurrent.CopyOnWriteArrayList;
public class Tester {
public static void main(String args[]) {
// create an array list
CopyOnWriteArrayList<String> al = new CopyOnWriteArrayList();
System.out.println("Initial size of al: " + al.size());
// add elements to the array list
al.add("C");
al.add("A");
al.add("E");
al.add("B");
al.add("D");
al.add("F");
al.add(1, "A2");
System.out.println("Size of al after additions: " + al.size());
// display the array list
System.out.println("Contents of al: " + al);
// Remove elements from the array list
al.remove("F");
al.remove(2);
System.out.println("Size of al after deletions: " + al.size());
System.out.println("Contents of al: " + al);
try{
Iterator<String> iterator = al.iterator();
while(iterator.hasNext()) {
iterator.remove();
}
}catch(UnsupportedOperationException e) {
System.out.println("Method not supported:");
}
System.out.println("Size of al: " + al.size());
}
}
This will produce the following result −
Output
Initial size of al: 0 Size of al after additions: 7 Contents of al: [C, A2, A, E, B, D, F] Size of al after deletions: 5 Contents of al: [C, A2, E, B, D] Method not supported: Size of al: 5
Updated on: 2020-06-21T12:23:44+05:30
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