The Stream count() method in Java returns the total count of elements in the Stream. It is a terminal operation, so we can not perform any other operation after it. It accepts a stream of elements and returns a long, representing the total count of elements.
Java Stream count() operation – examples
Example 1:
Get the total count of numbers in the list:
class Test {
public static void main(String[] args) {
List<Integer> numbers = new ArrayList<>(Arrays.asList(1, 7, 9, 22, 19, 18, 47, 3, 12, 29, 17, 44, 78, 99));
long totalCount = numbers.stream().count();
System.out.println("Total count of numbers: " + totalCount);
}
}
Output: Total count of numbers: 14
Example 2:
Get the total count of custom objects in a list:
class Student {
private String firstName;
private String lastName;
private int grade;
public Student(String firstName, String lastName, int grade) {
this.firstName = firstName;
this.lastName = lastName;
this.grade = grade;
}
}
class Test {
public static void main(String[] args) {
List<Student> students = getStudents();
long totalCount = students.stream().count();
System.out.println("Total count of students: " + totalCount);
}
private static List<Student> getStudents() {
List<Student> students = new ArrayList<>();
students.add(new Student("Steve", "Rogers", 8));
students.add(new Student("John", "Doe", 5));
students.add(new Student("Melissa", "Smith", 7));
students.add(new Student("Megan", "Norton", 4));
students.add(new Student("Tom", "Johnson", 9));
return students;
}
}
Output: Total count of students: 5
I hope this tutorial was helpful to you. To learn more, check out other Java Functional Programming tutorials.