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How to write the comparator as a lambda expression in Java?
A lambda expression is an anonymous method and doesn't execute on its own in java. Instead, it is used to implement a method defined by the functional interface. A lambda expression used with any functional interface and Comparator is a functional interface. The Comparator interface has used when sorting a collection of objects compared with each other.
In the below example, we can sort the employee list by name using the Comparator interface.
Example
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
class Employee {
int id;
String name;
double salary;
public Employee(int id, String name, double salary) {
super();
this.id = id;
this.name = name;
this.salary = salary;
}
}
public class LambdaComparatorTest {
public static void main(String[] args) {
List<Employee> list = new ArrayList<Employee>();
// Adding employees
list.add(new Employee(115, "Adithya", 25000.00));
list.add(new Employee(125, "Jai", 30000.00));
list.add(new Employee(135, "Chaitanya", 40000.00));
System.out.println("Sorting the employee list based on the name");
// implementing lambda expression
Collections.sort(list, (p1, p2) -> {
return p1.name.compareTo(p2.name);
});
for(Employee e : list) {
System.out.println(e.id + " " + e.name + " " + e.salary);
}
}
}Output
Sorting the employee list based on the name 115 Adithya 25000.0 135 Chaitanya 40000.0 125 Jai 30000.0
Updated on: 06-Dec-2019
4K+ Views
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