Comparing and Sorting list objects based on their multiple attributes

Comparing and Sorting list objects 

There are multiple ways to sort objects available in list collection based on their multiple attributes which we can treat as keys. We will see the example below where we will sort list of objects. These objects are available as pojo(plain old java objects) forms.

Employee.java

package com.gaurav.compare.lists;

/**

 * @author Gaurav

 *

 */

public class Employee {

    private String empName;

    private String designation;

    private int age;

    private int salary;

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

        this.empName = name;

        this.designation = jobTitle;

        this.age = age;

        this.salary = salary;

    }

    public String toString() {

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

    }

public String getEmpName() {

return empName;

}

public void setEmpName(String empName) {

this.empName = empName;

}

public String getDesignation() {

return designation;

}

public void setDesignation(String designation) {

this.designation = designation;

}

public int getAge() {

return age;

}

public void setAge(int age) {

this.age = age;

}

public int getSalary() {

return salary;

}

public void setSalary(int salary) {

this.salary = salary;

}

}

ComparatorChain.java

package com.gaurav.compare.lists;

/**

 * @author Gaurav

 *

 */

import java.util.Arrays;

import java.util.Comparator;

import java.util.List;

public class ComparatorChain implements Comparator<Employee>{

private List<Comparator<Employee>> lstComparators;

 

    @SafeVarargs

public ComparatorChain(Comparator<Employee>... comparators) {

        this.lstComparators = Arrays.asList(comparators);

    }

    @Override

    public int compare(Employee employee1, Employee employee2) {

        for (Comparator<Employee> comparator : lstComparators) {

            int finalResult = comparator.compare(employee1, employee2);

            if (finalResult != 0) {

                return finalResult;

            }

        }

        return 0;

    }

}

DesignationComparator.java

package com.gaurav.compare.lists;

/**

 * @author Gaurav

 *

 */

import java.util.Comparator;

public class DesignationComparator implements Comparator<Employee>{

 @Override

   public int compare(Employee employee1, Employee employee2) {

       return employee1.getDesignation().compareTo(employee2.getDesignation());

   }

}

AgeComparator.java

package com.gaurav.compare.lists;

/**

 * @author Gaurav

 *

 */

import java.util.Comparator;

public class AgeComparator implements Comparator<Employee>{

 @Override

   public int compare(Employee employee1, Employee employee2) {

       return employee1.getAge() - employee2.getAge();

   }

}

SalaryComparator.java

package com.gaurav.compare.lists;

/**

 * @author Gaurav

 *

 */

import java.util.Comparator;

public class SalaryComparator implements Comparator<Employee>{

@Override

    public int compare(Employee employee1, Employee employee2) {

        return employee1.getSalary() - employee2.getSalary();

    }

}

ListObjectsComparisonAndSortingExample.java

package com.gaurav.compare.lists;

/**

 * @author Gaurav

 *

 */

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

public class ListObjectsComparisonAndSortingExample {

public static void main(String[] args) {

 

       System.out.println("# COMPARING AND SORTING LIST OBJECTS BASED ON MULTIPLE ATTRIBUTES #\n");

 

       List<Employee> employeesList = new ArrayList<Employee>();

 

       employeesList.add(new Employee("Tusaar", "Developer", 44, 82000));

       employeesList.add(new Employee("Suresh", "Designer", 32, 77500));

       employeesList.add(new Employee("Bimlesh", "Designer", 44, 141900));

       employeesList.add(new Employee("Piyush", "Programmer", 26, 65700));

       employeesList.add(new Employee("Tiya", "Designer", 44, 131300));

       employeesList.add(new Employee("Culinan", "Programmer", 31, 55000));

       employeesList.add(new Employee("Amit", "Programmer", 27, 58000));

       employeesList.add(new Employee("Aaditya", "Designer", 31, 155000));

       employeesList.add(new Employee("Bimal", "Programmer", 24, 39000));

       employeesList.add(new Employee("Smith", "Developer", 29, 89000));

       employeesList.add(new Employee("Jimmy", "Developer", 36, 69000));

       employeesList.add(new Employee("Peter", "Developer", 38, 152000));

       employeesList.add(new Employee("Ali", "Programmer", 37, 85000));

       employeesList.add(new Employee("Dravid", "Developer", 33, 10000));

       employeesList.add(new Employee("Jatin", "Designer", 34, 83250));

 

       System.out.println("*** Displaying the employee list objects before sorting:\n");

 

       for (Employee employee : employeesList) {

           System.out.println(employee);

       }

 

       Collections.sort(employeesList, new ComparatorChain(

               new DesignationComparator(),

               new AgeComparator(),

               new SalaryComparator())

       );

 

       System.out.println("\n*** Displaying the employee list objects after sorting:\n");

 

       for (Employee employee : employeesList) {

           System.out.println(employee);

       }

 

   }

}

Result:-

# COMPARING AND SORTING LIST OBJECTS BASED ON MULTIPLE ATTRIBUTES #

*** Displaying the employee list objects before sorting:

Tusaar Developer 44 82000
Suresh Designer 32 77500
Bimlesh Designer 44 141900
Piyush Programmer 26 65700
Tiya Designer 44 131300
Culinan Programmer 31 55000
Amit Programmer 27 58000
Aaditya Designer 31 155000
Bimal Programmer 24 39000
Smith Developer 29 89000
Jimmy Developer 36 69000
Peter Developer 38 152000
Ali Programmer 37 85000
Dravid Developer 33 10000
Jatin Designer 34 83250

*** Displaying the employee list objects after sorting:

Aaditya Designer 31 155000
Suresh Designer 32 77500
Jatin Designer 34 83250
Tiya Designer 44 131300
Bimlesh Designer 44 141900
Smith Developer 29 89000
Dravid Developer 33 10000
Jimmy Developer 36 69000
Peter Developer 38 152000
Tusaar Developer 44 82000
Bimal Programmer 24 39000
Piyush Programmer 26 65700
Amit Programmer 27 58000
Culinan Programmer 31 55000
Ali Programmer 37 85000