LinkedHashSet - fail-safe or fail-fast iteration using iterator, Enumeration and enhanced for loop program.
iterator returned by LinkedHashSet is fail-fast. Means any structural modification made to LinkedHashSet like adding or removing elements during Iteration will throw java.util.ConcurrentModificationException.
import java.util.Collections;
import java.util.Enumeration;
import java.util.LinkedHashSet;
import java.util.Iterator;
import java.util.Set;
/**
* Copyright (c), AnkitMittal JavaMadeSoEasy.com
*/
public class LinkedHashSetIteratorFailFastExample {
public static void main(String args[]) {
Set<String> linkedLinkedHashSet = new LinkedHashSet<String>();
linkedLinkedHashSet.add("ankit");
linkedLinkedHashSet.add("javaMadeSoEasy");
System.out.println("-------use iterator-------");
// fail-fast
Iterator<String> iterator = linkedLinkedHashSet.iterator();
while (iterator.hasNext()) {
linkedLinkedHashSet.add("newElement1");//unComment to avoid ConcurrentModificationException
System.out.println(iterator.next());
}
System.out.println("-------use Enumeration-------");
// fail-fast
Enumeration<String> listEnum = Collections.enumeration(linkedLinkedHashSet);
while (listEnum.hasMoreElements()) {
linkedLinkedHashSet.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 : linkedLinkedHashSet) {
linkedLinkedHashSet.add("newElement3");//unComment to avoid ConcurrentModificationException
System.out.println(string);
}
}
}
/*OUTPUT
-------use iterator-------
Exception in thread "main" java.util.ConcurrentModificationException
at java.util.LinkedHashMap$LinkedHashIterator.nextNode(Unknown Source)
at java.util.LinkedHashMap$LinkedKeyIterator.next(Unknown Source)
at LinkedHashSetIteratorFailFastExample.main(LinkedHashSetIteratorFailFastExample.java:25)
*/
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