How to use iterator in java

Iterator in Java is a tool used to traverse collections. Usage methods include: Obtaining an Iterator: Use the iterator() method of the Collection interface. Loop through the collection: use hasNext() to check if the next element exists, use next() to get the current element and move to the next element.

Usage of Iterator in Java

What is Iterator?

The Iterator interface is a tool in the Java programming language for traversing collections. It provides a set of methods that allow the programmer to access each element in the collection sequentially.

Usage of Iterator:

1. Get Iterator:

   • Use Collection interface iterator() Method gets the Iterator of the collection.

2. Loop through the collection:

   • Use the hasNext() method to check whether the Iterator still exists The next element.
   • If there is, use the next() method to get the current element and move to the next element.

Sample code:

// 创建一个字符串集合
Set<String> names = new HashSet<>();
names.add("Alice");
names.add("Bob");
names.add("Carol");

// 获取集合的 Iterator
Iterator<String> iterator = names.iterator();

// 循环遍历集合
while (iterator.hasNext()) {
    String name = iterator.next();
    System.out.println(name);
}

Advantages:

• Flexibility: Iterator can be used to traverse various types of collections, including List, Set and Map.
• Sequential traversal: Iterator provides an ordered way to traverse the elements in a collection.
• Avoid concurrent modifications: Using Iterator can avoid concurrent modifications to the collection when traversing the collection, thereby preventing data corruption.

Note:

Iterator is a read-only interface and cannot be used to modify elements in the collection. If you need to modify the collection, you need to use other methods, such as List.set() or Map.put().

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