Java LongStream average()用法及代码示例

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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