Java Iterator and Iterable: Unlocking the Mysteries of Java Collection Traversal

Java Iterator and Iterable are very important concepts in Java programming. They provide us with a convenient way to traverse collections. For beginners, these two interfaces may cause some confusion, but as long as they understand their principles and usage, they can be easily mastered. In this article, we will delve into the mysteries of Java Iterator and Iterable to help readers better understand and apply them. Come with PHP editor Yuzi to uncover the mystery of Java collection traversal!

Iterator interface is an interface defined in Java CollectionFramework, which provides a series of methods for traversing collection elements. The Iterator interface defines the following main methods:

• hasNext(): Returns a Boolean value indicating whether the next element exists.
• next(): Returns the next element. If there is no next element, throws NoSuchElementException exception.
• remove(): Delete the currently pointed element.

The following is sample code for traversing a collection using the Iterator interface:

List<String> list = new ArrayList<>();
list.add("Hello");
list.add("World");
list.add("!");

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

while (iterator.hasNext()) {
String element = iterator.next();
System.out.println(element);
}

Iterable interface

The Iterable interface is another interface defined in the Java collection framework, which represents an iterable collection. The Iterable interface defines the following main methods:

• iterator(): Returns an Iterator object for traversing collection elements.

The implementation class of the Iterable interface only needs to implement the iterator() method to provide the function of traversing collection elements. The following is sample code for traversing a collection using the Iterable interface:

List<String> list = new ArrayList<>();
list.add("Hello");
list.add("World");
list.add("!");

for (String element : list) {
System.out.println(element);
}

The difference between Iterator and Iterable

Iterator and Iterable are two important interfaces in the Java collection framework for traversing collections. Their main differences are:

• Iterator is a concrete class that provides a variety of methods to traverse collection elements, while Iterable is just an interface, which only provides an iterator() method to return an Iterator object.
• Iterator can be used directly to traverse collection elements, while Iterable needs to first call the iterator() method to obtain an Iterator object, and then use the Iterator object to traverse the collection elements.
• Iterator can delete elements while traversing the collection elements, while Iterable cannot delete elements directly, and needs to delete elements through an Iterator object.

Summarize

Iterator and Iterable are two important interfaces in the Java collection framework for traversing collections. They provide a unified traversal method for collections. The Iterator interface provides a variety of methods to iterate over collection elements and delete elements while traversing collection elements. The Iterable interface only needs to implement an iterator() method to return an Iterator object, and then use the Iterator object to traverse the collection elements.

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