Sort Arraylist: Reordering Your Data

sort arraylistIn the computer programming industry, an ArrayList is an upgraded version of a standard computer array, in the sense that it is a data structure that provides a program with the ability to access data objects directly with an index number. This saves both the user and computer time, as those data objects can be accessed instantly instead of having to work through a full sequence of data just to find the relevant information.

While a typical computer array is set at a fixed size and cannot be modified during program execution to store any more or less data than was originally planned, an ArrayList can grow or shrink as needed at any point. For this very reason, ArrayLists are also referred to as dynamic arrays. To learn more about using ArrayLists in C# or Java, you can refer to this arraylist tutorial for beginners on the Udemy blog.If you think of yourself as an aspiring programmer but don’t have much of a background in the field yet, a great way to get started is to try this course on C# for complete beginners. The C# programming language is a great way to introduce yourself to the industry and can help you learn the basics of coding, something all programmers must be very proficient in.

The Basics

Depending on the programming language you work with, the process of sorting an ArrayList may vary, but the most common language you are likely to be working with when you find the need to sort your data is Java. There are multiple methods of sorting an ArrayList in Java, but the most common practice is to use the Collections API (application programming interface). This method is fairly simple and can quickly reorder the elements you’ve entered in a more natural looking ascending order. To use this method, enter your elements into the ArrayList and invoke sort (List list) API method of Collections, and your data will automatically be rearranged in an ascending manner.

It may not always be that simple with Java, however. If you wanted to sort a custom object, for instance, you will need a slightly more complicated approach. You’ll have two options in this case: the comparable or comparator interface. When you’re trying to sort customized data, attempting to run the Collections API will result in an error message, so the goal in using either one of these methods is to clear the way for Collections.sort to run properly.

Comparable Interface vs Comparative Interface

The comparable interface is simple enough. Simply designate which custom object you want to sort by and implement the comparable interface and override the compareTo method, and afterwards the Collections API will do its job. Unfortunately, the comparable interface only works when you’re trying to sort a single property, which should be an integer.

This might work wonderfully if all you need to do is sort a list of students by age, or a group of employees by salary, but if you need to sort by multiple properties, you’ll have to use the comparator interface. With this approach, you’ll want to override the compare method of Comparator before designating which properties you want to sort by. Using this method, you would be able to sort both by salary as well as another property, like tenure for example. Unless you’re trying to compare a list of properties directly with other objects in that class, you’ll need to go with the comparative method.

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