HashSet - fail-safe or fail-fast iteration using iterator, Enumeration and enhanced for loop program






HashSet - fail-safe or fail-fast iteration using iterator, Enumeration and enhanced for loop program.


iterator returned by HashSet is fail-fast. Means any structural modification made to HashSet like adding or removing elements during Iteration will throw java.util.ConcurrentModificationException.



import java.util.Collections;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
/**
* Copyright (c), AnkitMittal JavaMadeSoEasy.com
*/
public class HashSetTest {
   public static void main(String args[]) {
          Set<String> hashSet = new HashSet<String>();
          hashSet.add("ankit");
          hashSet.add("javaMadeSoEasy");
          System.out.println("-------use iterator-------");
          // fail-fast
          Iterator<String> iterator = hashSet.iterator();
          while (iterator.hasNext()) {
                 hashSet.add("newElement1");//unComment to avoid ConcurrentModificationException
                 System.out.println(iterator.next());
          }
          System.out.println("-------use Enumeration-------");
          // fail-fast
          Enumeration<String> listEnum = Collections.enumeration(hashSet);
          while (listEnum.hasMoreElements()) {
                 hashSet.add("newElement2");//unComment to avoid ConcurrentModificationException
                 System.out.println(listEnum.nextElement());
          }
          System.out.println("-------use enhanced for loop-------");
          // enhanced for loop is fail-fast
          for (String string : hashSet) {
                 hashSet.add("newElement3");//unComment to avoid ConcurrentModificationException
                 System.out.println(string);
          }
   }
}



RELATED LINKS>


HashSet - iterate using iterator, Enumeration and enhanced for loop program


HashSet - making set unmodifiable using Collections.unmodifiableSet


CopyOnWriteArraySet - add, contains, remove, size methods program


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