DoubleStream findFirst() returns an OptionalDouble (a container object which may or may not contain a non-null value) describing the first element of this stream, or an empty OptionalDouble if the stream is empty.
Syntax :
OptionalDouble findFirst()
Parameters :
- OptionalDouble : A container object which may or may not contain a non-null value.
Return Value : The function returns an OptionalDouble describing the first element of this stream, or an empty OptionalDouble if the stream is empty.
Note : findFirst() is a terminal-short-circuiting operation of Stream interface. This method returns any first element satisfying the intermediate operations.
Example 1 : findFirst() method on Double Stream.
// Java code for DoubleStream findFirst()// which returns an OptionalDouble describing// first element of the stream, or an// empty OptionalDouble if the stream is empty.import java.util.*;import java.util.stream.DoubleStream;  class GFG {      // Driver code    public static void main(String[] args)    {        // Creating an DoubleStream        DoubleStream stream = DoubleStream.of(6.2, 7.3, 8.4, 9.5);          // Using DoubleStream findFirst() to return        // an OptionalDouble describing first element        // of the stream        OptionalDouble answer = stream.findFirst();          // if the stream is empty, an empty        // OptionalDouble is returned.        if (answer.isPresent())            System.out.println(answer.getAsDouble());        else            System.out.println("no value");    }} |
Output :
6.2
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 DoubleStream findFirst()// which returns an OptionalDouble describing// first element of the stream, or an// empty OptionalDouble if the stream is empty.import java.util.OptionalDouble;import java.util.stream.DoubleStream;  class GFG {      // Driver code    public static void main(String[] args)    {        // Creating an DoubleStream        DoubleStream stream = DoubleStream.of(4.7, 4.5,                     8.0, 10.2, 12.0, 16.0).parallel();          // Using DoubleStream findFirst().        // Executing the source code multiple times        // must return the same result.        // Every time you will get the same        // Double value which is divisible by 4.        stream = stream.filter(num -> num % 4.0 == 0);          OptionalDouble answer = stream.findFirst();        if (answer.isPresent())            System.out.println(answer.getAsDouble());    }} |
Output :
8.0
