Java.Util.Comparable is an interface used for sorting
collections. In previous example, we used a MultyField Comparable to sort a
list in ascending order by multiple fields. In this example, we will implement
a reverse order multy field Comparable in order to achieve a sorting in
descending order or in other words in reverse order of whatever is implemented
in the Comparable. This can be achieved just by a single line of code as
Comparator c= Collections.reverseOrder();// yes a
comparator is used to achieve it.
This example is almost a replica of the previous example. It
consists of the following 2 classes.
Employee.java:
package
com.soft.model;
public
class Employee{
private
String name;
private
String department;
private
int age;
public
String getName() {
return name;
}
public
void setName(String name) {
this.name = name;
}
public
String getDepartment() {
return department;
}
public
void setDepartment(String department) {
this.department = department;
}
public
int getAge() {
return age;
}
public
void setAge(int age) {
this.age = age;
}
@Override
public
int compareTo(Object obj) {
Employee employee=(Employee)obj;
if(this.getName().compareTo(employee.getName())==0){
if(this.getDepartment().compareTo(employee.getDepartment())==0){
return
this.getAge()-employee.getAge();
}else{
return
this.getDepartment().compareTo(employee.getDepartment());
}
}else{
return this.getName().compareTo(employee.getName());
}
}
}
MultyFieldComparableExample.java:
package com.soft.examples;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import com.soft.model.Employee;
public class MultyFieldComparableExample {
public
static void main(String[] args) {
List<Employee>
list= new ArrayList<Employee>();
Employee
e=new Employee();
e.setName("Danial
Fritz");
e.setDepartment("Field
Based Development");
e.setAge(36);
list.add(e);
e=new Employee();
e.setName("Denis
Khoo");
e.setDepartment("Project
Management");
e.setAge(30);
list.add(e);
e=new
Employee();
e.setName("Joe
Kum");
e.setDepartment("Adminstration");
e.setAge(40);
list.add(e);
e=new Employee();
e.setName("Anil
Kumar");
e.setDepartment("Information
Technology");
e.setAge(26);
list.add(e);
e=new
Employee();
e.setName("Anil
Kumar");
e.setDepartment("Information
Technology");
e.setAge(26);
list.add(e);
e=new Employee();
e.setName("Anil
Kumar");
e.setDepartment("Information
Technology");
e.setAge(25);
list.add(e);
e=new
Employee();
e.setName("Anil
Kumar");
e.setDepartment("Project
Management");
e.setAge(26);
list.add(e);
System.out.println("************
Before Sorting ***********");
for
(int i=0;i< list.size();i++){
System.out.println(list.get(i).getName()+"-----"+list.get(i).getDepartment()+"-----"+list.get(i).getAge());
}
System.out.println("**Name,
Department, Age Sorting through Comparable **");
Collections.sort(list);
for
(int i=0;i< list.size();i++){
System.out.println(list.get(i).getName()+"-----"+list.get(i).getDepartment()+"-----"+list.get(i).getAge());
}
System.out.println("**
Name, Department, Age Sorting through Comparable In Descending Order**");
Collections.sort(list,Collections.reverseOrder());
for
(int i=0;i< list.size();i++){
System.out.println(list.get(i).getName()+"-----"+list.get(i).getDepartment()+"-----"+list.get(i).getAge());
}
}
}
Output:
************
Before Sorting ***********
Danial
Fritz ----- Field Based
Development ----- 36
Denis
Khoo ----- Project Management ----- 30
Joe
Kum ----- Adminstration ----- 40
Anil
Kumar ----- Information
Technology ----- 26
Anil
Kumar ----- Information Technology ----- 26
Anil
Kumar ----- Information
Technology ----- 25
Anil
Kumar-----Project Management-----26
**
Name, Department, Age Sorting through Comparable **
Anil
Kumar ----- Information
Technology ----- 25
Anil
Kumar ----- Information
Technology ----- 26
Anil
Kumar ----- Information
Technology ----- 26
Anil
Kumar ----- Project Management ----- 26
Danial
Fritz ----- Field Based
Development ----- 36
Denis
Khoo ----- Project Management ----- 30
Joe Kum -----
Adminstration ----- 40
**
Name, Department, Age Sorting through Comparable in Descending Order**
Joe
Kum ----- Adminstration ----- 40
Denis
Khoo ----- Project Management ----- 30
Danial
Fritz ----- Field Based Development ----- 36
Anil
Kumar ----- Project Management ----- 26
Anil
Kumar ----- Information Technology ----- 26
Anil
Kumar ----- Information Technology ----- 26
Anil Kumar ----- Information
Technology ----- 25
An example of a simple MultyField Comparable can be found at
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