Core Java Concepts and Syntax

How to sort a list in Java?

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How to sort a list in Java?

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Introduction

The secret to transparent interviews with product-based organizations is data structure and algorithm. Java's List data structure is one of these crucial ones. In the post below, we'll talk regarding Java List Sort and methods to employ Collections Sort to sort lists in Java.

List in Java

In Java, lists contain methods for inserting, deleting, updating, and searching the elements. These methods are indexed to maintain the ordered collection. In contrast to C++ sets, they also let duplicate and null members be added. Java's java.util package is necessary in order to use the list interface.

It may be viewed as a source of ListIterators that we can utilize to iterate across the list both forward and backward. Lists can be used in applications such as Vectors, Stacks, ArrayLists and LinkedLists Let's examine several Java List Sort techniques.

Java List Sort

Collections.sort is the method most frequently used in Java to specify how to sort lists (). This method's only prerequisite for sorting is that every member in the list implements a similar interface.

The Java list sort notion is crucial to understanding Java. It is a classic interview challenge. Let's examine some examples of how to use the Collections.sort() method to sort various lists.

Sort Strings List

The Java List is used to refer to all different forms of lists in the phrase "Java List Sort." The list of strings is one of these significant lists. Using the string class's implementation of the Collections.sort() function to order a list of strings Similar interface:

package com.boardinfinity.sort;

import java.util.ArrayList;
import java.util.List;
import java.util.Collections;

public class stringListSort {
      public static void main(String[] args) {
            List<String> stringList = new ArrayList<String>();
        stringList.add("abc");
        stringList.add("cde");
        stringList.add("efg");
        stringList.add("bcd");


            //Using Collections sort method for Java List Sort.
        Collections.sort(stringList);
        for (String s : stringList)
              System.out.print(" " + s);
      }
}


Output
abc bcd cde efg 

write your code here: Coding Playground

Sort Objects List

The list of items must be addressed when we are studying Java list sort. Here, we'll use the Collections.sort() function to order a list of custom objects. Only classes that implement the Comparable interface are able to utilize this function.

package com.boardinfinity.sort;

import java.util.ArrayList;
import java.util.List;
import java.util.Collections;

// Defining a new class for the object.
class objData implements Comparable<objData> {

      private int val;

      public objData(int i) {
        this.val = i;
      }

      @Override
      public int compareTo(objData d) {
        return this.val - d.getVal();
      }

      @Override
      public String toString() {
        return "objData{" + this.val + "}";
      }

      public int getVal() {
        return val;
      }
}

public class objectListSort {

      // Main Function.
      public static void main(String[] args) {
            List<objData> objList = new ArrayList<>();

            // Inserting Data.
        objList.add(new objData(2));
        objList.add(new objData(3));
        objList.add(new objData(1));

            // Printing and Sorting.
        System.out.println("List Before Sorting::" + objList);

// Java List Sort with Collections sort.
        Collections.sort(objList);

        System.out.println("List After Sorting::" + objList);

      }

}

Output

List Before Sorting::[objData{2}, objData{3}, objData{1}]

List After Sorting::[objData{1}, objData{2}, objData{3}]

write your code here: Coding Playground

Sort List using a Comparator

To sort a list according to our specified criteria, we may override the Collections sort function and give our own Comparator implementation. Since Comparator is a functional interface, we often utilize lambda expressions to create the implementation of Comparator in a single line.

Collections.sort(objList, (l1, l2) -> {
  return l2.getVal() - l1.getVal();
});
System.out.println("List objects using Comparator in descending order:" + objList);
Output
List objects using Comparator in descending order::[objData{3}, objData{2}, objData{1}]

FAQs

  1. Define lists in Java.

The items that are indexed and searchable in Java lists are stored using methods for inserting, deleting, updating, and preserving the ordered collection. In contrast to C++ sets, they also let duplicate and null members be added.

2. What does Java List Sort mean to you?

Java List Sort is the process of rearranging list items so that they are in ascending order by some property.

3. Which Java list sorting technique is the most popular?

Collections sort is the most used technique in Java for sorting lists.

4. How are Lists implemented differently in Java?

There are numerous ways to implement lists in Java, including array lists, linked lists, vectors, stacks, etc.

5. What Java package is necessary to use the List interface?

Java's java.util package is necessary in order to use the list interface.

Conclusion

We learned about Java List Sort and how to sort lists in Java in the article above. We mainly concentrated on the collections- sort approach, which is the most used way.