Java 8中的java.util.stream.LongStream处理原始Longs。它有助于解决旧问题，例如以新的方式在数组中找到最大值，在数组中找到最小值，数组中所有元素的总和以及数组中所有值的平均值。 LongStream average()返回一个OptionalDouble，描述此流的元素的算术平均值；如果此流为空，则返回一个空的Optional。
用法：
OptionalDouble average()
Where, OptionalDouble is a container object
which may or may not contain a double value.
示例1:
// Java code for LongStream average()
import java.util.*;
import java.util.stream.LongStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// creating a stream
LongStream stream = LongStream.of(2L, 3L, 4L,5L, 6L, 7L, 8L);
// OptionalDouble is a container object
// which may or may not contain a
// doouble value.
OptionalDouble obj = stream.average();
// If a value is present, isPresent() will
// return true and getAsDouble() will
// return the value
if (obj.isPresent()) {
System.out.println(obj.getAsDouble());
}else {
System.out.println("-1");
}
}
}
输出：
5.0
示例2：
// Java code for LongStream average()
import java.util.*;
import java.util.stream.LongStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// creating a stream
LongStream stream = LongStream.of(2L, 3L, 4L,5L, 6L, 7L, 8L);
// OptionalDouble is a container object
// which may or may not contain a
// doouble value.
OptionalLong obj2 = stream.max();
// If a value is present, isPresent() will
// return true and getAsDouble() will
// return the value
if (obj2.isPresent()) {
System.out.println(obj2.getAsLong());
}else {
System.out.println("-1");
}
}
}
输出：
8
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