Java 8中如何将Iterator转换为Stream呢?

下文笔者讲述jdk8中将Iterator转换为Stream的方法分享,如下所示

Iterator转Stream的实现思路

使用StreamSupport.stream方法即可
   将Iterator转换为Stream 

例:
  // Iterator -> spliterators -> Stream
  Stream<String> stream = StreamSupport.stream(
                Spliterators.spliteratorUnknownSize(
                        iterator,
                        Spliterator.ORDERED)
                , false);

ator 。

StreamSupport源码

public static <T> Stream<T> stream(Spliterator<T> spliterator, boolean parallel) {
      Objects.requireNonNull(spliterator);
      return new ReferencePipeline.Head<>(spliterator,
                                          StreamOpFlag.fromCharacteristics(spliterator),
                                          parallel);
  }

迭代器->流的示例

由于Iterator接口没有spliterator()方法
所以需要使用Spliterators.spliteratorUnknownSize将Iterator转换为Spliterator
再使用StreamSupport.stream将Spliterator转换为Stream

package com.java265;
 
import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;
 
public class JavaStreamExample1 {
 
    public static void main(String[] args) {
 
        list<String> list = new ArrayList<>();
        list.add("java265");
        list.add("java");
        list.add("c#");
        list.add("spring boot");
        list.add("python");
 
        Iterator<String> iterator = list.iterator();
 
        // Iterator -> Spliterators -> Stream -> List
        List<Integer> result = StreamSupport.stream(
                Spliterators.spliteratorUnknownSize(iterator, Spliterator.ORDERED), false)
                .map(x -> x.length())
                .collect(Collectors.toList());
 
        result.forEach(x -> System.out.println(x));
        System.out.println(result.getClass());
 
    } 
}

可迭代->流

由于Iterable接口拥有spliterator()方法
所以非常方便就可以将其转换为Stream

package com.java265;
 
import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;
 
public class JavaStreamExample2 {
 
    public static void main(String[] args) {
 
        Iterable<Integer> iterable = Arrays.asList(88,99,110,222,333);
 
        // Iterable -> Spliterators -> Stream -> List
        List<Integer> result = StreamSupport.stream(
                iterable.spliterator(), false)
                .map(x -> x * 10)
                .collect(Collectors.toList());
 
        result.forEach(x -> System.out.println(x));
        System.out.println(result.getClass());
 
    }
}