使用Java流来收集在for循环中生成的对象 [英] Use Java streams to collect objects generated in a `for` loop

问题描述

我们如何使用Java Streams方法来收集在中为循环生成的对象？

例如

，这里我们生成一个 LocalDate 对象rel =nofollow noreferrer> YearMonth 通过反复调用 YearMonth :: atDay 。

  YearMonth ym = YearMonth.of（2017，Month.AUGUST）; 
列表< LocalDate> dates = new ArrayList<>（ym.lengthOfMonth（））; 
 for（int i = 1; i< = ym.lengthOfMonth（）; i ++）{
 LocalDate localDate = ym.atDay（i）; 
 dates.add（localDate）; 
 
 
 
 $ b $ p 
 $ b 
可以用流重写吗？
 <可以用IntStream开始重写： 
 
 
  YearMonth ym = YearMonth.of（2017，Month.AUGUST）; 
列表< LocalDate>日期= 
 IntStream.rangeClosed（1，ym.lengthOfMonth（））
 .mapToObj（ym :: atDay）
 .collect（Collectors.toList（））; 
  
将IntStream中的每个整数值映射到所需日期，然后将日期收集到列表中。
 
How can we use the Java Streams approach to collecting objects generated in a for loop?

For example, here we generate one LocalDate object for each day in a month represented by YearMonth by repeatedly calling YearMonth::atDay. 
YearMonth ym = YearMonth.of( 2017 , Month.AUGUST ) ;
List<LocalDate> dates = new ArrayList<>( ym.lengthOfMonth() );
for ( int i = 1 ; i <= ym.lengthOfMonth () ; i ++ ) {
    LocalDate localDate = ym.atDay ( i );
    dates.add( localDate );
}
Can this be rewritten using streams?
解决方案
It can be rewritten starting with an IntStream:
YearMonth ym = YearMonth.of(2017, Month.AUGUST);
List<LocalDate> dates =
        IntStream.rangeClosed(1, ym.lengthOfMonth())
        .mapToObj(ym::atDay)
        .collect(Collectors.toList());
Each integer value from the IntStream is mapped to the desired date and then the dates are collected in a list.

                        
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