Java中迭代器和分离器的区别

// Java program to illustrate Iterator interface

import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
public class JavaIteratorExample1 {
    public static void main(String[] args)
    {

        // create a linkedlist
        List<String> list = new LinkedList<>();

        // Add elements
        list.add("Welcome");
        list.add("to");
        list.add("our");
        list.add("website");

        // print the list to the console
        System.out.println("The list is given as : " + list);

        // call iterator on the list
        Iterator<String> itr = list.iterator();

        // itr.hasNext() returns true if there is still an element next to the current element pointed by iterator
        while (itr.hasNext()) {
            // Returns the next element.
            System.out.println(itr.next());
        }

        // Removes the last element.
        itr.remove();

        // print the list after removing an element
        System.out.println("After the remove() method is called : "+ list);
    }
}

运行结果:

The list is given as : [Welcome, to, our, yiibai]
Welcome
to
our
yiibai
After the remove() method is called : [Welcome, to, our]

像Iterator和ListIterator一样,Spliterator也是一个Java Iterator,它被用来从List实现的对象中逐一迭代元素。

Spliterator的主要功能是:

  • 分割源数据
  • 处理源数据

JDK 8中包含了接口Spliterator,以便在顺序遍历之外利用并行的优势。它被设计成一个迭代器的并行类似物。

// Java program to illustrate a Spliterator

import java.util.*;
import java.util.stream.Stream;

public class InterfaceSpliteratorExample {

    public static void main(String args[])
    {

        // Create an object of array list
        ArrayList<Integer> list = new ArrayList<>();

        // Add elements to the array list
        list.add(101);
        list.add(201);
        list.add(301);
        list.add(401);
        list.add(501);

        // create a stream on the list
        Stream<Integer> str = list.stream();

        // Get Spliterator object on stream
        Spliterator<Integer> splitr = str.spliterator();

        // Get size of the list encountered by the forEachRemaining method
        System.out.println("Estimate size: " + splitr.estimateSize());

        // Print getExactSizeIfKnown returns exact size if finite or return -1
        System.out.println("Exact size: "+ splitr.getExactSizeIfKnown());

        // Check if the Spliterator has all
        // the characteristics
        System.out.println("Boolean Result: "+ splitr.hasCharacteristics(splitr.characteristics()));

        System.out.println("Elements of ArrayList :");

        // print elements using forEachRemaining
        splitr.forEachRemaining((n) -> System.out.println(n));

        // Obtaining another Stream to the array list.
        Stream<Integer> str1 = list.stream();

        splitr = str1.spliterator();

        // Obtain spliterator using     trySplit() method
        Spliterator<Integer> splitr2 = splitr.trySplit();

        // If splitr can be partitioned use splitr2 first.
        if (splitr2 != null) {
            System.out.println("Output from splitr2: ");
            splitr2.forEachRemaining(
                (n) -> System.out.println(n));
        }

        // Now, use the splitr
        System.out.println("Output from splitr1: ");
        splitr.forEachRemaining(
            (n) -> System.out.println(n));
    }
}

运行结果:

Estimate size: 5
Exact size: 5
Boolean Result: true
Elements of ArrayList :
101
201
301
401
501
Output from splitr2: 
101
201
Output from splitr1: 
301
401
501

java中迭代器和迭代器的区别

迭代器 迭代器
引入于Java 1.2 引入于Java 1.8
迭代器只对元素进行单独迭代 迭代器对元素进行单独和批量的追踪
迭代器是整个集合API的一个迭代器 迭代器是集合和流API的一个迭代器,除了Map实现类之外
迭代器使用外部迭代 迭代器使用内部迭代。
迭代器是一个通用迭代器 迭代器不是一个通用迭代器
迭代器不支持并行编程 迭代器通过分割给定的元素集来支持并行编程,这样每个元素集可以被单独处理。