Java List sort() Method with Examples

by Online Tutorials Library July 22, 2022

Java List sort() Method

The sort() method of List Interface sorts the given list according to the order specified in the comparator. The list must be modifiable else it will throw an exception.

Syntax

Parameters

The parameter ‘c’ represents the Comparator used to compare list elements. And for null values, natural ordering is used.

Return

Throws:

ClassCastException- If the list contains elements that are not mutually comparable using the comparator

UnsupportedOperationException– If the list’s list-iterator does not support the sort operation

IllegalArgumentException– If the comparator is found to violate the Comparator protocols.

Example 1

  import java.util.Collections;  import java.util.LinkedList;  import java.util.List;  public class JavaListSubListExample3 {  public static void main(String[] args) {          List<String> list= new LinkedList<>();  list.add(“Renu”);  list.add(“Heera”);  list.add(“Vijay”);  list.add(“Geetanjali”);  System.out.println(“List : “+list);  //will sort the string acc to the alphabets  Collections.sort(list);  System.out.println(“Sorted List : “+list);      }  }  

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Output:

List : [Renu, Heera, Vijay, Geetanjali]  Sorted List : [Geetanjali, Heera, Renu, Vijay]

Example 2

  import java.util.ArrayList;  import java.util.Collections;  import java.util.Comparator;  import java.util.List;    class Employee {    int id;      String name;    public Employee(int id, String name) {  this.id = id;  this.name = name;      }  public String toString()      {  return this.id + ” ” + this.name ;        }  }  class SortById implements Comparator<Employee> {  // Used for sorting in ascending order of ID  public int compare(Employee a, Employee b)      {  return a.id – b.id;      }  }    // Main class  class JavaListSubListExample2 {  static int i=1;  public static void main (String[] args) {          List<Employee> list = new ArrayList<Employee>();          Employee employee1 = new Employee(15019, “Patanjali”);          Employee employee2 = new Employee(13198, “Geetanjali”);          Employee employee3 = new Employee(12112, “Anjali”);  list.add(employee1);  list.add(employee2);  list.add(employee3);  System.out.println(“Unsorted List : “);  for (Employee val : list) {  System.out.println(i++ +”. “+val);          }  Collections.sort(list, new SortById());  System.out.println();  System.out.println(” Sorted List : “);  int i=1;  for (Employee val : list) {  System.out.println(i++ +”. “+val);          }      }  }  

Test it Now

Output:

Unsorted List :  1. 15019 Patanjali  2. 13198 Geetanjali  3. 12112 Anjali     Sorted List :  1. 12112 Anjali  2. 13198 Geetanjali  3. 15019 Patanjali

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