DoubleStream mapToLong() returns a LongStream consisting of the results of applying the given function to the elements of this stream.
Note : DoubleStream mapToLong() is a intermediate operation. These operations are always lazy. Intermediate operations are invoked on a Stream instance and after they finish their processing, they give a Stream instance as output.
Syntax :
LongStream mapToLong(DoubleToLongFunction mapper)
Parameters :
- DoubleStream : A sequence of primitive double-valued elements. This is the double primitive specialization of Stream.
- mapper : A stateless function to apply to each element.
Return Value : The function returns a LongStream consisting of the results of applying the given function to the elements of this stream.
Example 1 :
// Java code for LongStream mapToLong// (DoubleToLongFunction 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 a DoubleStream        DoubleStream stream = DoubleStream.of(3.3, 6.5, 16.4,                                              8.7, 10.4);          // Using LongStream mapToLong(DoubleToLongFunction mapper)        // to return a LongStream consisting of the        // results of applying the given function to        // the elements of this stream.        LongStream stream1 = stream.mapToLong(num -> (long)num);          // Displaying the elements in stream1        stream1.forEach(System.out::println);    }} |
Output :
3 6 16 8 10
Example 2 :
// Java code for LongStream mapToLong// (DoubleToLongFunction 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 a DoubleStream        DoubleStream stream = DoubleStream.of(3.3, 6.5, 16.4,                                              8.7, 10.4);          // Using LongStream mapToLong(DoubleToLongFunction mapper)        // to return a LongStream consisting of the        // results of applying the given function to        // the elements of this stream.        LongStream stream1 = stream.mapToLong(num -> (long)num - 10);          // Displaying the elements in stream1        stream1.forEach(System.out::println);    }} |
Output :
-7 -4 6 -2 0
Example 3 :
// Java code for LongStream mapToLong// (DoubleToLongFunction 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 a DoubleStream        DoubleStream stream = DoubleStream.of(3.3, 6.5, 16.4,                                              8.7, 10.4);          // Using LongStream mapToLong(DoubleToLongFunction mapper)        // to return a LongStream consisting of the        // results of applying the given function to        // the elements of this stream.        LongStream stream1 = stream.mapToLong(num -> (long)(2 * num * num));          // Displaying the elements in stream1        stream1.forEach(System.out::println);    }} |
Output :
21 84 537 151 216
