众所周知,Java9中引入了两个新的方法takeWhile和dropWhile,他们可以高效地选择或者丢弃流中的元素, 按照设定的大小,对流执行截断操作,从而提高效率。
这里,本汪提供了使用Java8,对这两个方法的实现,
希望可以帮到有需要的小伙伴
请注意,该操作与Java9所提供方法有所不同的是,本汪提供的实现为即时操作,不具备java9中延迟求值的特性
package com.tencent.collector;
import java.util.List;
import java.util.function.Predicate;
import java.util.stream.Stream;
/**
* 自定义Stream
* **
* Yuezejian Created in 2020/10/18 下午9:11
*/
public interface MyStream<T> extends Stream {
/**
* The list as param, must be sorted, this is the takeWhile() in java9
* But make it come true with java8
* Keep eligible elements
* Recommended when there are few eligible elements
* @param list
* @param p
* @param <T>
* @return <T>List<T>
*/
public static <T> List<T> takeWhile(List<T> list, Predicate<T> p) {
int i = 0;
for (T item : list) {
if (!p.test(item)) {
return list.subList(0,i);
}
i++;
}
return list;
}
/**
* The list as param, must be sorted, this is the dropWhile() in java9
* But make it come true with java8
* Discard elements that do not meet the criteria
* It is recommended to use when there are few unqualified elements
* @param list
* @param p
* @param <T>
* @return
*/
public static <T> List<T> dropWhile(List<T> list, Predicate<T> p) {
int i = 0;
for (T item : list) {
if (p.test(item)) {
return list.subList(i,list.size());
}
i++;
}
return list;
}
}