Java中的 DoubleSummaryStatistics combine() 方法及示例

Java中 DoubleSummaryStatistics 类的combine()方法用于将给定的其他 DoubleSummaryStatistics 组合到此 DoubleSummaryStatistics。

句法：

public void combine(DoubleSummaryStatistics 
                otherDoubleSummaryStatistics)

参数：此方法接受otherDoubleSummaryStatistics作为要组合到此 DoubleSummaryStatistics 中的参数。

返回值：此方法不返回任何内容。

异常：如果 otherDoubleSummaryStatistics 为 null，则此方法抛出NullPointerException 。

程序：

// Java program to demonstrate
// the above method
  
import java.util.*;
  
public class DoubleSummaryStatisticsDemo {
    public static void main(String[] args)
    {
  
        DoubleSummaryStatistics doubleSummaryStatistics
            = new DoubleSummaryStatistics();
  
        List list = new LinkedList<>();
        list.add(95.7);
        list.add(234.6767);
        list.add(243.5);
        list.add(50.0);
        list.add(45.6);
  
        Iterator iterator = list.listIterator();
        while (iterator.hasNext()) {
  
            // Add the doubles to the
            // DoubleSummaryStatistics object
            doubleSummaryStatistics
                .accept(iterator.next());
        }
  
        System.out.println("First DdoubleSummaryStatistics: "
                           + doubleSummaryStatistics
                                 .toString());
  
        DoubleSummaryStatistics otherDoubleSummaryStatistics
            = new DoubleSummaryStatistics();
  
        List list1 = new LinkedList<>();
        list1.add(45664.0);
        list1.add(7007.777);
        list1.add(5677.0);
        list1.add(0.0);
        list1.add(45664.7);
  
        Iterator iterator1 = list1.listIterator();
        while (iterator1.hasNext()) {
  
            // Add the doubles to the
            // DoubleSummaryStatistics object
            otherDoubleSummaryStatistics
                .accept(iterator1.next());
        }
  
        System.out.println("Second DdoubleSummaryStatistics: "
                           + otherDoubleSummaryStatistics
                                 .toString());
  
        System.out.println("Combining both DdoubleSummaryStatistics"
                           + " using combine() ");
        doubleSummaryStatistics.combine(otherDoubleSummaryStatistics);
  
        System.out.println("Combined DdoubleSummaryStatistics: "
                           + doubleSummaryStatistics.toString());
    }
}

输出：

First DdoubleSummaryStatistics:
DoubleSummaryStatistics{count=5, sum=669.476700, min=45.600000, average=133.895340, max=243.500000}
Second DdoubleSummaryStatistics:
DoubleSummaryStatistics{count=5, sum=104013.477000, min=0.000000, average=20802.695400, max=45664.700000}

Combining both DdoubleSummaryStatistics using combine()

Combined DdoubleSummaryStatistics:
DoubleSummaryStatistics{count=10, sum=104682.953700, min=0.000000, average=10468.295370, max=45664.700000}

参考： https://docs.oracle.com/javase/9/docs/api/ Java/util/DoubleSummaryStatistics.html#combine-java.util.DoubleSummaryStatistics-