Java 中的 LongStream sum()
LongStream sum() 返回该流中元素的总和。这是减的特例。LongStream sum()是一个 终端操作 ，也就是说，它可能会遍历该流以产生结果或副作用。
注:约简操作(也称为折叠)取一系列输入元素，通过重复应用组合操作(如求一组数字的和或最大值)将它们组合成单个汇总结果。
语法:
long sum()
返回值:函数返回该流中元素的总和。
例 1 :
// Java code for LongStream.sum() to
// find the sum of elements in LongStream
import java.util.*;
import java.util.stream.LongStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating an LongStream
LongStream stream = LongStream.of(2L, 4L, 6L, -2L, -4L);
// Using LongStream.sum() to find
// sum of elements in LongStream
long sumOfElements = stream.sum();
// Displaying the calculated sum
System.out.println(sumOfElements);
}
}
Output:
6
例 2 :
// Java code for LongStream.sum() to
// find the sum of elements
// divisible by 3 in given range
import java.util.*;
import java.util.stream.LongStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Using LongStream.sum() to find
// sum of elements dividible by 3
// in given range
long sumOfElements = LongStream.range(2L, 10L)
.filter(num -> num % 3 == 0)
.sum();
// Displaying the calculated sum
System.out.println(sumOfElements);
}
}
Output:
18
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