Java - Stream - 收集每 N 个元素
我正在尝试学习 java - 流.我能够做简单的迭代/过滤/映射/收集等.
I am trying to learn java - stream. I am able to do simple iteration / filter / map / collection etc.
当我尝试收集每 3 个元素并按此示例中所示打印时，[收集每 3 个元素并打印等等...]
When I was kind of trying to collect every 3 elements and print as shown here in this example, [collect every 3 elements and print and so on...]
List<String> list = Arrays.asList("a","b","c","d","e","f","g","h","i","j");
int count=0;
String append="";
for(String l: list){
if(count>2){
System.out.println(append);
System.out.println("-------------------");
append="";
count=0;
}
append = append + l;
count++;
}
System.out.println(append);
输出:
abc
-------------------
def
-------------------
ghi
-------------------
j
我不知道如何使用流来做到这一点.我应该实现自己的收集器来实现这一点吗?
I am not getting any clue how to do this using stream. Should i implement my own collector to achieve this?
推荐答案
您实际上可以使用 IntStream 来模拟列表的分页.
You can actually use an IntStream to simulate your list's pagination.
List<String> list = Arrays.asList("a","b","c","d","e","f","g","h","i","j");
int pageSize = 3;
IntStream.range(0, (list.size() + pageSize - 1) / pageSize)
.mapToObj(i -> list.subList(i * pageSize, Math.min(pageSize * (i + 1), list.size())))
.forEach(System.out::println);
哪个输出:
[a, b, c]
[d, e, f]
[g, h, i]
[j]
如果你想生成字符串，你可以使用 String.join 因为你是直接处理一个 List<String>:
If you want to generate Strings, you can use String.join since you are dealing with a List<String> directly:
.mapToObj(i -> String.join("", list.subList(i * pageSize, Math.min(pageSize * (i + 1), list.size()))))
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