Stream findFirst() in Java with examples
Last Updated :
06 Dec, 2018
Stream findFirst() returns an Optional (a container object which may or may not contain a non-null value) describing the first element of this stream, or an empty Optional if the stream is empty. If the stream has no encounter order, then any element may be returned.
Syntax :
Optional<T> findFirst()
Where, Optional is a container object which
may or may not contain a non-null value
and T is the type of objects and the function
returns an Optional describing the first element
of this stream, or an empty Optional if the stream is empty.
Exception : If the element selected is null, NullPointerException is thrown.
Note : findAny() is a terminal-short-circuiting operation of Stream interface. This method returns first element satisfying the intermediate operations.
Example 1 : findFirst() function on Stream of Integers.
import java.util.*;
class GFG {
public static void main(String[] args)
{
List<Integer> list = Arrays.asList( 3 , 5 , 7 , 9 , 11 );
Optional<Integer> answer = list.stream().findFirst();
if (answer.isPresent()) {
System.out.println(answer.get());
}
else {
System.out.println( "no value" );
}
}
}
|
Output :
3
Example 2 : findFirst() function on Stream of Strings.
import java.util.*;
class GFG {
public static void main(String[] args)
{
List<String> list = Arrays.asList( "GeeksforGeeks" , "for" ,
"GeeksQuiz" , "GFG" );
Optional<String> answer = list.stream().findFirst();
if (answer.isPresent()) {
System.out.println(answer.get());
}
else {
System.out.println( "no value" );
}
}
}
|
Output :
GeeksforGeeks
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