Java Iterator and Iterable: An in-depth analysis of Java collection traversal mechanism

Iterator interface

Iterator and Iterable in Java are key interfaces in the Java collection framework, which provide convenience for traversing collections. In this article, PHP editor Xinyi will deeply analyze the working principles of Iterator and Iterable in Java to help readers better understand the traversal mechanism of Java collections.

• hasNext(): Check if there are more elements in the collection.
• next(): Returns the next element in the collection.

The

Iterator interface also defines some optional methods, such as the remove() method, which is used to remove the current element from the collection.

Use Iterator interface

You can use the following steps to traverse a collection using the Iterator interface:

1. Get the Iterator object of the collection.
2. Use the hasNext() method to check if there are more elements in the collection.
3. If there are more elements, use the next() method to get the next element.
4. Repeat steps 2 and 3 until there are no more elements in the set.

The following is an example of using the Iterator interface to traverse an ArrayList:

import java.util.ArrayList;
import java.util.Iterator;

public class IteratorExample {

public static void main(String[] args) {
// 创建一个 ArrayList
ArrayList<String> names = new ArrayList<>();

// 向 ArrayList 中添加一些元素
names.add("John");
names.add("Mary");
names.add("Bob");

// 获取 ArrayList 的 Iterator 对象
Iterator<String> iterator = names.iterator();

// 使用 Iterator 对象遍历 ArrayList
while (iterator.hasNext()) {
String name = iterator.next();
System.out.println(name);
}
}
}

Iterable interface

The Iterable interface is a high-level interface in the Java collection framework for traversing collections. It defines an iterator() method that returns an Iterator object.

Use Iterable interface

You can use the following steps to traverse a collection using the Iterable interface:

1. Get the Iterable object of the collection.
2. Use the iterator() method to obtain an Iterator object.
3. Use an Iterator object to traverse the collection.

The following is an example of using the Iterable interface to traverse an ArrayList:

import java.util.ArrayList;
import java.util.Iterable;

public class IterableExample {

public static void main(String[] args) {
// 创建一个 ArrayList
ArrayList<String> names = new ArrayList<>();

// 向 ArrayList 中添加一些元素
names.add("John");
names.add("Mary");
names.add("Bob");

// 获取 ArrayList 的 Iterable 对象
Iterable<String> iterable = names;

// 使用 Iterable 对象获取一个 Iterator 对象
Iterator<String> iterator = iterable.iterator();

// 使用 Iterator 对象遍历 ArrayList
while (iterator.hasNext()) {
String name = iterator.next();
System.out.println(name);
}
}
}

The difference between Iterator and Iterable interfaces

Iterator and Iterable interfaces are both interfaces for traversing collections, but there are some differences between them.

• Iterator is a low-level interface that directly operates on the elements in the collection.
• Iterable is a high-level interface that operates elements in the collection through the Iterator interface.
The
• Iterator interface defines two main methods: hasNext() and next().
• The Iterable interface defines only one method: iterator().

When to use the Iterator interface and when to use the Iterable interface

Generally speaking, if you need to directly operate the elements in the collection, you can use the Iterator interface. If you only need to iterate over the elements in a collection, you can use the Iterable interface.

For example, if you need to remove elements from a collection, you can use the remove() method of the Iterator interface. If you only need to traverse the elements in the collection, you can use the iterator() method of the Iterable interface to obtain an Iterator object, and then use the Iterator object to traverse the collection.

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