LongStream findFirst() returns an OptionalLong (a container object which may or may not contain a non-null value) describing the first element of this stream, or an empty OptionalLong if the stream is empty
Syntax :
OptionalLong findFirst()
Parameters :
- OptionalLong : A container object which may or may not contain a non-null value.
Return Value : The function returns an OptionalLong describing the first element of this stream, or an empty OptionalLong if the stream is empty.
Note : findAny() is a terminal-short-circuiting operation of Stream interface. This method returns any first element satisfying the intermediate operations.
Example 1 : findFirst() method on Long Stream.
// Java code for LongStream findFirst() // which returns an OptionalLong describing // first element of the stream, or an // empty OptionalLong if the stream is empty. 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(6L, 7L, 8L, 9L);
// Using LongStream findFirst() to return
// an OptionalLong describing first element
// of the stream
OptionalLong answer = stream.findFirst();
// if the stream is empty, an empty
// OptionalLong is returned.
if (answer.isPresent())
System.out.println(answer.getAsLong());
else
System.out.println( "no value" );
}
} |
Output :
6
Note : If the stream has no encounter order, then any element may be returned.
Example 2 : findFirst() method to return the first element which is divisible by 4.
// Java code for LongStream findFirst() // which returns an OptionalLong describing // first element of the stream, or an // empty OptionalLong if the stream is empty. import java.util.OptionalLong;
import java.util.stream.LongStream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Creating an LongStream
LongStream stream = LongStream.of(4L, 5L, 8L, 10L, 12L, 16L)
.parallel();
// Using LongStream findFirst().
// Executing the source code multiple times
// must return the same result.
// Every time you will get the same
// value which is divisible by 4.
stream = stream.filter(num -> num % 4 == 0 );
OptionalLong answer = stream.findFirst();
if (answer.isPresent())
System.out.println(answer.getAsLong());
}
} |
Output :
4