The thenComparingLong(java.util.function.ToLongFunction) method of Comparator Interface in Java returns a lexicographic-order comparator with a function that extracts a Long sort key.
Syntax:
default Comparator <T> thenComparingLong(
ToLongFunction <T> keyExtractor)
Parameters: This method accepts keyExtractor which is the function used to extract the Long sort key.
Return value: This method returns a lexicographic-order comparator composed of this and then the Long sort key.
Exception: This method throws NullPointerException if the argument is null.
Below programs illustrate thenComparingLong(java.util.function.ToLongFunction) method:
Program 1:
// Java program to demonstrate Comparator// thenComparingLong(ToLongFunction) method import java.util.Arrays;import java.util.Collections;import java.util.Comparator;import java.util.List; public class GFG { public static void main(String... args) { List<Users> list = createUsers(); System.out.printf("before sort: %s%n", list); Collections.sort(list, Comparator .comparing(Users::getDepartment) .thenComparingLong(Users::getId)); System.out.printf("after sort: %s%n", list); } private static List<Users> createUsers() { return Arrays.asList( new Users(12311, "ME"), new Users(10211, "CSE"), new Users(33111, "CSE"), new Users(21000, "IT"), new Users(12133, "IT"), new Users(21445, "CSE")); } private static class Users { private long id; private String department; public Users(long id, String department) { this.id = id; this.department = department; } public long getId() { return id; } public void setId(long id) { this.id = id; } public String getDepartment() { return department; } public void setDepartment(String department) { this.department = department; } @Override public String toString() { return department + " - " + id; } }} |
The output printed on console of IDE is shown below.
Output:
You can see in example first sorting is done on department wise and if the department is same then ID wise.
Program 2:
// Java program to demonstrate Comparator// thenComparingLong(ToLongFunction) method import java.util.Arrays;import java.util.Comparator;import java.util.List; public class GFG { public static void main(String... args) { List<String> list = Arrays.asList("KKR", "CSK", "MI", "KXIP", "RCB", "SRH", "DC", "RR"); try { // apply thenComparingLong Comparator.comparing(list::get) .thenComparingLong(null); } catch (Exception e) { System.out.printf("Exception:" + e); } }} |
The output printed on console is shown below.
Output:
