Sorting List by using Comparator Interface
Table of Contents
In this article, I am going to explain the Sorting List by using Comparator Interface. Objects Type List can be sorted by using a Comparator interface. By using comparator we can sort the list of objects by a single field or multiple fields either in ascending order or descending order.
Here we have student data like first name, last name, and city. We can sort the student data by student first name either in ascending order or descending order.
Sort By Single Field
- StudentVo.java
- StudentDataCreate.java
- StudentFirstNameSorter.java
- ComparatorSorterBySingleField.java
Sort By Multiple Fields
- StudentVo.java
- StudentDataCreate.java
- StudentFirstNameSorter.java
- StudentLastNameSorter.java
- ComparatorSorterByMultipleFields.java
Sort By Single Field
StudentVo.java
package com.narayanatutorial.Comparator.SortBySingleFiled;
public class StudentVo {
String studentFirstName;
String studentLastName;
String studentCity;
public String getStudentFirstName() {
return studentFirstName;
}
public void setStudentFirstName(String studentFirstName) {
this.studentFirstName = studentFirstName;
}
public String getStudentLastName() {
return studentLastName;
}
public void setStudentLastName(String studentLastName) {
this.studentLastName = studentLastName;
}
public String getStudentCity() {
return studentCity;
}
public void setStudentCity(String studentCity) {
this.studentCity = studentCity;
}
}
StudentDataCreate.java
package com.narayanatutorial.Comparator.SortBySingleFiled;
import java.util.ArrayList;
import java.util.List;
public class StudentDataCreate {
private List<StudentVo> list;
public List<StudentVo> getStudentData() {
list = new ArrayList<StudentVo>();
StudentVo st = null;
st = new StudentVo();
st.setStudentCity("Bangalore");
st.setStudentFirstName("Narayana1");
st.setStudentLastName("Ragi1");
list.add(st);
st = new StudentVo();
st.setStudentCity("Bangalore");
st.setStudentFirstName("Chandra");
st.setStudentLastName("Sekhar");
list.add(st);
st = new StudentVo();
st.setStudentCity("Chennai");
st.setStudentFirstName("Ravi");
st.setStudentLastName("Kumar2");
list.add(st);
st = new StudentVo();
st.setStudentCity("Mumbai");
st.setStudentFirstName("Ravi");
st.setStudentLastName("Kumar1");
list.add(st);
return list;
}
}
StudentFirstNameSorter.java
package com.narayanatutorial.Comparator.SortBySingleFiled;
import java.util.Comparator;
public class StudentFirstNameSorter implements Comparator<StudentVo> {
public int compare(StudentVo o1, StudentVo o2) {
return o1.getStudentFirstName().compareTo(o2.studentFirstName);
}
}
ComparatorSorterBySingleField.java
package com.narayanatutorial.Comparator.SortBySingleFiled;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class ComparatorSorterBySingleField {
public static void main(String args[]) {
StudentDataCreate sdc = new StudentDataCreate();
List<StudentVo> list = sdc.getStudentData();
System.out.println("Before First Name Sort \n***********************************");
System.out.println("FirstName # LastName # City\n***********************************");
list.forEach(x -> System.out
.println(x.getStudentFirstName() + " # " + x.getStudentLastName() + " # " + x.getStudentCity()));
// by using Comparator implemented class object
// Collections.sort(list, new StudentFirstNameSorter());
Collections.sort(list, new Comparator<StudentVo>() {
@Override
public int compare(StudentVo o1, StudentVo o2) {
//By Ascending Order
return o1.getStudentFirstName().compareTo(o2.getStudentFirstName());
//By Descending Order
//return o2.getStudentFirstName().compareTo(o1.getStudentFirstName());
}
});
System.out.println("\nAfter First Name Sort \n***********************************");
System.out.println("FirstName # LastName # City\n***********************************");
list.forEach(x -> System.out
.println(x.getStudentFirstName() + " # " + x.getStudentLastName() + " # " + x.getStudentCity()));
}
}
Output
Before First Name Sort *********************************** FirstName # LastName # City *********************************** Narayana1 # Ragi1 # Bangalore Chandra # Sekhar # Bangalore Ravi # Kumar2 # Chennai Ravi # Kumar1 # Mumbai After First Name Sort *********************************** FirstName # LastName # City *********************************** Chandra # Sekhar # Bangalore Narayana1 # Ragi1 # Bangalore Ravi # Kumar2 # Chennai Ravi # Kumar1 # Mumbai
Sort By Multiple Fields
ComparatorSorterByMultipleFields.java
package com.narayanatutorial.Comparator.SortByTwoFileds;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class ComparatorSorterByMultipleFields {
public static void main(String args[]) {
StudentDataCreate sdc=new StudentDataCreate();
List<StudentVo> list=sdc.getStudentData();
System.out.println("Before First Name and Last Name Sort \n***********************************");
System.out.println("FirstName # LastName # City\n***********************************");
list.forEach(x -> System.out.println(x.getStudentFirstName()+" # "+x.getStudentLastName()+" # "+x.getStudentCity()));
Collections.sort(list, new Comparator<StudentVo>() {
@Override
public int compare(StudentVo o1, StudentVo o2) {
//By Ascending Order
int i=o1.getStudentFirstName().compareTo(o2.getStudentFirstName());
//By Descending Order
//int i=o2.getStudentFirstName().compareTo(o1.getStudentFirstName());
System.out.println("i:"+i);
if(i != 0) {
return i;
}
//By Ascending Order
return o1.getStudentLastName().compareTo(o2.getStudentLastName());
//By Descending Order
//return o2.getStudentLastName().compareTo(o1.getStudentLastName());
}
});
System.out.println("\nAfter First Name and Last Name Sort \n***********************************");
System.out.println("FirstName # LastName # City\n***********************************");
list.forEach(x -> System.out.println(x.getStudentFirstName()+" # "+x.getStudentLastName()+" # "+x.getStudentCity()));
}
}
Output
Before First Name and Last Name Sort *********************************** FirstName # LastName # City *********************************** Narayana1 # Ragi1 # Bangalore Chandra # Sekhar # Bangalore Ravi # Kumar2 # Chennai Ravi # Kumar1 # Mumbai i:-11 i:15 i:4 i:4 i:0 After First Name and Last Name Sort *********************************** FirstName # LastName # City *********************************** Chandra # Sekhar # Bangalore Narayana1 # Ragi1 # Bangalore Ravi # Kumar1 # Mumbai Ravi # Kumar2 # Chennai
StudentLastNameSorter.java
package com.narayanatutorial.Comparator.SortByTwoFileds;
import java.util.Comparator;
public class StudentLastNameSorter implements Comparator<StudentVo> {
public int compare(StudentVo o1, StudentVo o2) {
return o1.getStudentLastName().compareTo(o2.getStudentLastName());
}
}
ComparatorSorterByMultipleFieldsByJava18Feature.java
Collections.sort(list, new StudentFirstNameSorter().thenComparing(new StudentLastNameSorter()));
package com.narayanatutorial.Comparator.SortByTwoFileds;
import java.util.Collections;
import java.util.List;
public class ComparatorSorterByMultipleFieldsByJava18Feature {
public static void main(String args[]) {
StudentDataCreate sdc = new StudentDataCreate();
List<StudentVo> list = sdc.getStudentData();
System.out.println("Before First Name and Last Name Sort \n***********************************");
System.out.println("FirstName # LastName # City\n***********************************");
list.forEach(x -> System.out
.println(x.getStudentFirstName() + " # " + x.getStudentLastName() + " # " + x.getStudentCity()));
Collections.sort(list, new StudentFirstNameSorter().thenComparing(new StudentLastNameSorter()));
System.out.println("\nAfter First Name and Last Name Sort \n***********************************");
System.out.println("FirstName # LastName # City\n***********************************");
list.forEach(x -> System.out
.println(x.getStudentFirstName() + " # " + x.getStudentLastName() + " # " + x.getStudentCity()));
}
}
Get full source code from Git.
Hello! I am Narayanaswamy founder and admin of narayanatutorial.com. I have been working in the IT industry for more than 12 years. NarayanaTutorial is my web technologies blog. My specialties are Java / J2EE, Spring, Hibernate, Struts, Webservices, PHP, Oracle, MySQL, SQLServer, Web Hosting, Website Development, and IAM(ForgeRock) Specialist
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