Iterator and ListIterator

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Iterator and ListIterator

Iterator and ListIterator are used to traverse collections in Java, but they have different features and capabilities.

1. Iterator

Available for all Collection types (List, Set, etc.).

Supports only forward traversal.

Can remove elements while iterating using remove().

Does not support modifying or adding elements.

Example:

java

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Iterator<String> it = list.iterator();

while(it.hasNext()) {

    System.out.println(it.next());

}

2. ListIterator

Available only for List implementations (like ArrayList, LinkedList).

Supports both forward and backward traversal.

Can add, remove, and modify elements during iteration.

Provides methods like hasPrevious(), previous(), add(), set().

Example:

java

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ListIterator<String> lit = list.listIterator();

while(lit.hasNext()) {

    System.out.println(lit.next());

}

Key Differences:

Feature Iterator ListIterator

Direction Forward only Forward & backward

Applicable to All Collections List only

Add/Modify Elements No Yes

Methods hasNext(), next() hasNext(), hasPrevious(), next(), previous(), add(), set()

Use Iterator for simple forward traversal, and ListIterator when you need more control over list navigation and modification.

Read More

HashMap, TreeMap

HashSet, TreeSet

ArrayList, LinkedList

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