2019-07-27 Stream类的collect

1.collect(Collectors.toList())

Stream language = Stream.of("java", "python", "C++","php","java");

List listResult = language.collect(Collectors.toList());

listResult.forEach(i->sout(i));

输出就是 java python c++ php java

toList()把stream变成一个list 且有序可重复

2.collect(Collectors.toSet()) 无序且不重复

Stream language = Stream.of("java", "python", "C++","php","java");

Set set = language.collect(Collectors.toSet());

set.forEach(i->sout(i));

结果：python C++ java php

3.joining拼接字符串

List list = Arrays.asList("java", "python", "C++","php","java");

    //直接将输出结果拼接

    sout(list.stream().collect(Collectors.joining()));

        //每个输出结果之间加拼接符号“|”

    sout(list.stream().collect(Collectors.joining(" | ")));

        //输出结果开始头为Start--，结尾为--End，中间用拼接符号“||”

    sout(list.stream().collect(Collectors.joining(" || ", "Start--", "--End")));

4.partitioningBy()

Stream l = Stream.of("java","python","C++","php","java");

Map> map = l.collect(Collectors.partitioningBy(s -> s.length() >3));

Iterator>> entry = map.entrySet().iterator();

while (entry.hasNext()){

Map.Entry> e = entry.next();

List list = e.getValue();

for (String list1 : list){

System.out.println(list1);

}

System.out.println("----------");

}

最终打印

C++

php

----------

java

python

java

----------