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);
}
}
}
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