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Iterator
Last Updated : 26 May, 2026
title: Iterator in Java
Collections Framework35 words5 headingsExamples included
title: Iterator in Java description: Collections ko iterate karne ke tarike
Collection elements ek-ek karke access karna.
Iterator Interface
List<String> list = new ArrayList<>(Arrays.asList("Java", "Python", "C++"));
Iterator<String> it = list.iterator();
while (it.hasNext()) {
String s = it.next();
System.out.println(s);
if (s.equals("Python")) it.remove(); // Safe removal
}
ListIterator (Bidirectional)
java exampleWoHoTech
List<Integer> list = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));
ListIterator<Integer> lit = list.listIterator(list.size()); // End se start
// Backward iteration
while (lit.hasPrevious()) {
System.out.print(lit.previous() + " "); // 5 4 3 2 1
}
// Forward + modify
ListIterator<Integer> lit2 = list.listIterator();
while (lit2.hasNext()) {
int n = lit2.next();
lit2.set(n * 2); // Replace with double
}for-each (Iterable)
java exampleWoHoTech
for (String s : list) System.out.println(s);forEach method (Java 8)
java exampleWoHoTech
list.forEach(s -> System.out.println(s));
list.forEach(System.out::println);fail-fast vs fail-safe
java exampleWoHoTech
// fail-fast (ArrayList, HashMap) — modification pe exception
List<Integer> list = new ArrayList<>(Arrays.asList(1, 2, 3));
for (Integer n : list) {
list.remove(n); // ConcurrentModificationException!
}
// fail-safe (CopyOnWriteArrayList) — copy par iterate
List<Integer> safe = new CopyOnWriteArrayList<>(Arrays.asList(1, 2, 3));
for (Integer n : safe) {
safe.remove(n); // OK, no exception
}Exam Focus
Revise definitions, diagrams, examples, and short-answer points for Iterator.
Interview Use
Prepare one clear explanation, one practical example, and one common mistake for this Java topic.
Search Terms
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Collections FrameworkJava Collections Frameworktitle: Collections Framework OverviewCollections FrameworkCollections Practice Programstitle: Collections ProgramsCollections FrameworkComparable vs Comparatortitle: Comparable vs ComparatorCollections FrameworkGenericstitle: Generics in JavaCollections FrameworkArrayListtitle: ArrayList in JavaCollections FrameworkLinkedListtitle: LinkedList in Java