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
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