Java 中的 LongStream mapToDouble()
哎哎哎:# t0]https://www . geeksforgeeks . org/long stream-maptopoble-Java/
LongStream mapToDouble() 返回一个 DoubleStream，由给定函数应用于该流元素的结果组成。
注: LongStream mapToDouble()是一个的中间操作。 这些操作总是偷懒。中间操作在流实例上被调用，在它们完成处理后，它们给出一个流实例作为输出。 语法:**
DoubleStream mapToDouble(LongToDoubleFunction mapper)
参数:
- 双流:原始双值元素的序列。这就是流的双原始特化。
- 映射器:应用于每个元素的无状态函数。
返回值:该函数返回一个双流，该双流由给定函数应用于该流元素的结果组成。
例 1 :
// Java code for DoubleStream mapToDouble
// (LongToDoubleFunction mapper)
import java.util.*;
import java.util.stream.LongStream;
import java.util.stream.DoubleStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating an LongStream
LongStream stream = LongStream.of(2L, 4L, 6L, 8L, 10L);
// Using DoubleStream mapToLong(LongToDoubleFunction mapper)
// to return a DoubleStream consisting of the
// results of applying the given function to
// the elements of this stream.
DoubleStream stream1 = stream.mapToDouble(num -> (double)num);
// Displaying the elements in stream1
stream1.forEach(System.out::println);
}
}
输出:
2.0
4.0
6.0
8.0
10.0
例 2 :
// Java code for DoubleStream mapToDouble
// (LongToDoubleFunction mapper)
import java.util.*;
import java.util.stream.LongStream;
import java.util.stream.DoubleStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating an LongStream
LongStream stream = LongStream.range(5L, 10L);
// Using DoubleStream mapToLong(LongToDoubleFunction mapper)
// to return a DoubleStream consisting of the
// results of applying the given function to
// the elements of this stream.
DoubleStream stream1 = stream.mapToDouble(num -> (double)num / 5);
// Displaying the elements in stream1
stream1.forEach(System.out::println);
}
}
输出:
1.0
1.2
1.4
1.6
1.8
例 3 :
// Java code for DoubleStream mapToDouble
// (LongToDoubleFunction mapper)
import java.util.*;
import java.util.stream.LongStream;
import java.util.stream.DoubleStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating an LongStream
LongStream stream = LongStream.range(5L, 10L);
// Using DoubleStream mapToLong(LongToDoubleFunction mapper)
// to return a DoubleStream consisting of the
// results of applying the given function to
// the elements of this stream.
DoubleStream stream1 = stream.mapToDouble(Math::cos);
// Displaying the elements in stream1
stream1.forEach(System.out::println);
}
}
输出:
0.28366218546322625
0.9601702866503661
0.7539022543433046
-0.14550003380861354
-0.9111302618846769
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