[Java基础]Stream流的常见生成方式

Posted 2021-08-15 Wecccccccc

1.Collection体系的集合可以使用默认方法stream()生成流
default Stream< E > stream()

代码如下:

package StreamTest;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Stream;

public class StreamDemo01 {
    public static void main(String[] args)
    {
        List<String> list = new ArrayList<String>();
        Stream<String> listStream = list.stream();

        Set<String> set = new HashSet<String>();
        Stream<String> setStream = set.stream();
        
    }
}

2.Map体系的集合间接的生成流

代码如下:

package StreamTest;

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

public class StreamDemo01 {
    public static void main(String[] args)
    {
        Map<String,Integer> map = new HashMap<String,Integer>();

        Stream<String> keyStream = map.keySet().stream();
        Stream<Integer> valueStream = map.values().stream();
        Stream<Map.Entry<String, Integer>> entryStream = map.entrySet().stream();

    }
}

3.数组可以通过Stream接口的静态方法of(T… values)生成流

代码如下:

package StreamTest;

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

public class StreamDemo01 {
    public static void main(String[] args)
    {
      String[] strArray = {"hello","java","world"};
      Stream<String> strArrayStream = Stream.of(strArray);
        Stream<String> strArrayStream02 = Stream.of("hello", "java", "world");
        Stream<Integer> intStream = Stream.of(10,20,30);

    }
}