Apache CompareToBuilder - Sort Employees with Age + JobTitle + Salary

public class Employee {

    private String name;

    private String jobTitle;

    private int age;

    private int salary;

    public Employee(String name, String jobTitle, int age, int salary) {

        this.name = name;

        this.jobTitle = jobTitle;

        this.age = age;

        this.salary = salary;

    }

    // getters and setters

    public String toString() {

        return String.format("%s\t%s\t%d\t%d", name, jobTitle, age, salary);

    }

}

Job title comparator:

public class EmployeeJobTitleComparator implements Comparator {

    @Override

    public int compare(Employee emp1, Employee emp2) {

        return emp1.getJobTitle().compareTo(emp2.getJobTitle());

    }

}

Age comparator:

public class EmployeeAgeComparator implements Comparator {

    @Override

    public int compare(Employee emp1, Employee emp2) {

        return emp1.getAge() - emp2.getAge();

    }

}

Salary comparator:

public class EmployeeSalaryComparator implements Comparator {

    @Override

    public int compare(Employee emp1, Employee emp2) {

        return emp1.getSalary() - emp2.getSalary();

    }

}

Using a Chained Comparator

public class EmployeeChainedComparator implements Comparator {

 

    private List> listComparators;

 

    @SafeVarargs

    public EmployeeChainedComparator(Comparator... comparators) {

        this.listComparators = Arrays.asList(comparators);

    }

 

    @Override

    public int compare(Employee emp1, Employee emp2) {

        for (Comparator comparator : listComparators) {

            int result = comparator.compare(emp1, emp2);

            if (result != 0) {

                return result;

            }

        }

        return 0;

    }

}

 

 

Using in Test Main Program

 

//pass the List and ChainedComparator

Collections.sort(listEmployees, new EmployeeChainedComparator(

                new EmployeeJobTitleComparator(),

                new EmployeeAgeComparator(),

                new EmployeeSalaryComparator())

        );

 

        System.out.println("\n*** After sorting:");

 

        for (Employee emp : listEmployees) {

            System.out.println(emp);

        }

 

Using a CompareToBuilder

import org.apache.commons.lang3.builder.CompareToBuilder;

public class EmployeeComparator implements Comparator {

    @Override

    public int compare(Employee o1, Employee o2) {

        return new CompareToBuilder()

                .append(o1.getJobTitle(), o2.getJobTitle())

                .append(o1.getAge(), o2.getAge())

                .append(o1.getSalary(), o2.getSalary())

                .toComparison();

    }

}

Switching sort order: ascending to descending

To reverse sort order from ascending to descending of a particular attribute, simply swap the order of the two objects being compared in the comparator. For example, the following comparator sorts the list by job title and age in ascending order, but by salary in descending order:

 public int compare(Employee o1, Employee o2) {

        return new CompareToBuilder()

                .append(o1.getJobTitle(), o2.getJobTitle())

                .append(o1.getAge(), o2.getAge())

                .append(o2.getSalary(), o1.getSalary())

                .toComparison();

    }