Learn The Techniques For SORTING CUSTOM OBJECTS In Java
Learn the techniques for sorting custom objects in Java. What is the difference between the Comparator and Comparable interfaces and which one should you use? Find out what situations can cause a runtime exception that will cause your application to crash. And as always, what are the security implications of sorting objects. When writing code, remember to always Begin Secure!!
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Chapters
00:00 Introduction
00:32 Overview
00:52 Java Comparable vs Comparator
01:10 Java classes implementing the Comparable interface
02:30 What's the purpose of Comparator?
03:13 Coding example using Comparable and Comparator
05:47 Example code using the Comparator interface to sort objects
12:39 Application security discussion of the Comparator and Comparable interfaces
The question today is: how can you sort an arraylist of custom objects by a property.
And just to be clear, we want to be able to sort the arraylist of custom objects, regardless of the data type.
Great question
To answer the question, we need to discuss the difference between comparable vs comparator
Java.lang.comparable is an interface
Classes that implement the comparable interface provde a natural ordering of the data so they can be sorted automatically
When we say automatically, it simple means that the order is obvious to anyone.
For example, here we see some of the java classes that implement the comparable interface
They include classes such as byte, long, interger, short, double float, big inteter and bigdecimal.
Keep in mind that the numeric types – long, integer, float, double, etc – refer to the class wrappers and not the primitive types
The natural ordering for these classes is a signed numerical ordering
Next is character, the order for this class is unsigned numerical
The Boolean wrapper class also implements the comparable interface and in this case false comes before true
And we see a few more examples including file, string, date and collation key
If a class does not implement the comparable interface, you will get a classcast exception at runtime if you try to sort them.
The comparable interface consists of the following method
public int compareTo
which takes a type as an argument.
