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Java Academy · Lesson

ListIterator and Bidirectional Traversal

Use ListIterator to traverse lists forwards and backwards and modify elements during iteration.

ListIterator

ListIterator<T> extends Iterator<T> with backward traversal, index-based positioning, and the ability to add and replace elements during iteration.

ListIterator API

Additional methods beyond Iterator: hasPrevious(), previous(), nextIndex(), previousIndex(), set(), add().

import java.util.*;

List<String> list = new ArrayList<>(List.of("A", "B", "C", "D"));
ListIterator<String> lit = list.listIterator();

// Forward traversal
while (lit.hasNext()) {
    System.out.print(lit.nextIndex() + ":" + lit.next() + " ");
}
// 0:A 1:B 2:C 3:D

System.out.println();

// Backward traversal
while (lit.hasPrevious()) {
    System.out.print(lit.previousIndex() + ":" + lit.previous() + " ");
}
// 3:D 2:C 1:B 0:A

All lessons in this course

  1. The Iterable and Iterator Contracts
  2. Implementing a Custom Iterator
  3. ListIterator and Bidirectional Traversal
  4. Fail-Fast vs Fail-Safe Iterators
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