IntStream findFirst()在 Java
中
哎哎哎:# t0]https://www . geeksforgeeks . org/intstream-findfirst-Java/
IntStream findFirst() 返回一个optionallint(一个可能包含也可能不包含非空值的容器对象)，描述该流的 first 元素，如果该流为空，则返回一个空的 optionallint
语法:
OptionalInt findFirst()
Where, OptionalInt is a container object which
may or may not contain a non-null value
and the function returns an OptionalInt describing the
first element of this stream, or an empty OptionalInt
if the stream is empty.
注意: findFirst()是一个 端子-短路 操作的 Stream 界面。此方法返回满足中间操作的任何第一个元素。
示例 1 : 整数流上的 findFirst()方法。
// Java code for IntStream findFirst()
// which returns an OptionalInt describing
// first element of the stream, or an
// empty OptionalInt if the stream is empty.
import java.util.*;
import java.util.stream.IntStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating an IntStream
IntStream stream = IntStream.of(6, 7, 8, 9);
// Using IntStream findFirst() to return
// an OptionalInt describing first element
// of the stream
OptionalInt answer = stream.findFirst();
// if the stream is empty, an empty
// OptionalInt is returned.
if (answer.isPresent())
System.out.println(answer.getAsInt());
else
System.out.println("no value");
}
}
输出:
6
注意:如果流没有相遇顺序，那么可以返回任何元素。
示例 2 : findFirst()方法返回第一个可被 4 整除的元素。
// Java code for IntStream findFirst()
// which returns an OptionalInt describing
// first element of the stream, or an
// empty OptionalInt if the stream is empty.
import java.util.OptionalInt;
import java.util.stream.IntStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating an IntStream
IntStream stream = IntStream.of(4, 5, 8, 10, 12, 16)
.parallel();
// Using IntStream findFirst().
// Executing the source code multiple times
// must return the same result.
// Every time you will get the same
// Integer which is divisible by 4.
stream = stream.filter(num -> num % 4 == 0);
OptionalInt answer = stream.findFirst();
if (answer.isPresent())
System.out.println(answer.getAsInt());
}
}
输出:
4
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