Stream.count() method returns the number of elements in a stream. It is a terminal operation and a special case of reduction, which combines a sequence of elements into a single summary result. After performing count(), the stream is consumed and cannot be reused.
- Returns the total number of elements in the stream.
- Can be combined with intermediate operations like distinct(), filter(), etc.
- Consumes the stream once executed.
Example:
import java.util.*;
class GFG {
public static void main(String[] args) {
List<Integer> list = Arrays.asList(0, 2, 4, 6, 8, 10, 12);
long total = list.stream().count();
System.out.println(total);
}
}
Output
7
Explanation:
- Converts the list into a stream using list.stream().
- count() returns the total number of elements.
Syntax
long count()
- Parameters: This method does not take any parameters.
- Return Value: Returns a long representing the number of elements in the stream.
Example: This code shows how to count unique elements in a stream using distinct() with count().
import java.util.*;
class GFG {
public static void main(String[] args) {
List<String> list = Arrays.asList("GFG", "Geeks", "for", "Geeks", "GeeksforGeeks", "GFG");
long total = list.stream().distinct().count();
System.out.println(total);
}
}
Output
4
Explanation:
- distinct() removes duplicate elements from the stream.
- count() returns the total number of remaining elements in the stream.