IntStream findFirst() in Java

IntStream findFirst() returns an OptionalInt (a container object which may or may not contain a non-null value) describing the first element of this stream, or an empty OptionalInt if the stream is empty

Syntax :

OptionalInt findFirst()

Where, OptionalInt is a container object which
may or may not contain a non-null value 
and the function returns an OptionalInt describing the 
first element of this stream, or an empty OptionalInt
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 Integer Stream.

// Java code for IntStream findFirst()
// which returns an OptionalInt describing
// first element of the stream, or an
// empty OptionalInt if the stream is empty.
import java.util.*;
import java.util.stream.IntStream;

class GFG {

    // Driver code
    public static void main(String[] args)
    {
        // Creating an IntStream
        IntStream stream = IntStream.of(6, 7, 8, 9);

        // Using IntStream findFirst() to return
        // an OptionalInt describing first element
        // of the stream
        OptionalInt answer = stream.findFirst();

        // if the stream is empty, an empty
        // OptionalInt is returned.
        if (answer.isPresent())
            System.out.println(answer.getAsInt());
        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 IntStream findFirst()
// which returns an OptionalInt describing
// first element of the stream, or an
// empty OptionalInt if the stream is empty.
import java.util.OptionalInt;
import java.util.stream.IntStream;

class GFG {

    // Driver code
    public static void main(String[] args)
    {

        // Creating an IntStream
        IntStream stream = IntStream.of(4, 5, 8, 10, 12, 16)
                               .parallel();

        // Using IntStream findFirst().
        // Executing the source code multiple times
        // must return the same result.
        // Every time you will get the same
        // Integer which is divisible by 4.
        stream = stream.filter(num -> num % 4 == 0);

        OptionalInt answer = stream.findFirst();
        if (answer.isPresent())
            System.out.println(answer.getAsInt());
    }
}

Output :

4