Java中的 DoubleStream average() 示例

Java 8 中的Java .util.stream.DoubleStream处理原始双精度。它有助于以一种新的方式解决数组中的最大值，数组中的最小值，数组中所有元素的总和以及数组中所有值的平均值等老问题。 DoubleStream 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，则返回一个空的可选项。如果任何记录的值是 NaN 或总和在任何点都是 NaN，则平均值将为 NaN。
句法 ：

OptionalDouble average()

Where, OptionalDouble is a container object 
which may or may not contain a double value.

注意：返回的平均值可能因记录值的顺序而异。通过增加绝对量级排序的元素往往会产生更准确的结果。

示例 1：

// Java code for DoubleStream average()
import java.util.*;
import java.util.stream.DoubleStream;
  
class GFG {
  
    // Driver code
    public static void main(String[] args)
    {
        // creating a stream
        DoubleStream stream = DoubleStream.of(2.5, 3.6, 4.7, 5.0, 6.2);
  
        // OptionalDouble is a container object
        // which may or may not contain a
        // double 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：

4.4

示例 2：

// Java code for DoubleStream average()
import java.util.*;
import java.util.stream.DoubleStream;
  
class GFG {
  
    // Driver code
    public static void main(String[] args)
    {
        // OptionalDouble is a container object
        // which may or may not contain a
        // double value.
        OptionalDouble obj = DoubleStream.empty().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：

-1

示例 3：

// Java code for DoubleStream average()
import java.util.*;
import java.util.stream.DoubleStream;
  
class GFG {
  
    // Driver code
    public static void main(String[] args)
    {
        // creating a stream
        DoubleStream stream = DoubleStream.of(2.5, 3.6, 4.7,
                                              Double.MAX_VALUE, Double.MAX_VALUE);
  
        // OptionalDouble is a container object
        // which may or may not contain a
        // double 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：

Infinity