IntStream mapToLong() in Java - GeeksforGeeks

06 Dec, 2018
IntStream mapToLong() returns a LongStream consisting of the results of applying the given function to the elements of this stream.
Note : IntStream 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(IntToLongFunction mapper)

Parameters :
LongStream : A sequence of primitive long-valued elements. This is the long primitive specialization of Stream.mapper : A stateless function to apply to each element.
LongStream : A sequence of primitive long-valued elements. This is the long 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// (IntToLongFunction mapper)import java.util.*;import java.util.stream.IntStream;import java.util.stream.LongStream;  class GFG {      // Driver code    public static void main(String[] args)    {        // Creating an IntStream        IntStream stream = IntStream.of(2, 4, 6, 8, 10);          // Using LongStream mapToLong(IntToLongFunction 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 :
2
4
6
8
10

Example 2 :
// Java code for LongStream mapToLong// (IntToLongFunction mapper)import java.util.*;import java.util.stream.IntStream;import java.util.stream.LongStream;  class GFG {      // Driver code    public static void main(String[] args)    {        // Creating an IntStream        IntStream stream = IntStream.of(2, 4, 6, 8, 10);          // Using LongStream mapToLong(IntToLongFunction 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 + Integer.MAX_VALUE);          // Displaying the elements in stream1        stream1.forEach(System.out::println);    }}
Output :
2147483649
2147483651
2147483653
2147483655
2147483657

Example 3 :
// Java code for LongStream mapToLong// (IntToLongFunction mapper)import java.util.*;import java.util.stream.IntStream;import java.util.stream.LongStream;  class GFG {      // Driver code    public static void main(String[] args)    {        // Creating an IntStream        IntStream stream = IntStream.range(5, 10);          // Using LongStream mapToLong(IntToLongFunction 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 - 20);          // Displaying the elements in stream1        stream1.forEach(System.out::println);    }}
Output :
-15
-14
-13
-12
-11

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