Check if two objects are completely equal in Java

Question

I've got a Java class, here's an example:

public class Car {      private int fuelType;     private Date made;     private String name; . . . // and so on 

Now let's say I have two car objects and I want to compare if all their variables are equal.

Right now, I've solved this by overriding method equals(Object o) and I check if all the variables match in both objects.

The problem here is that if I have 20 classes, I'll have to override equals(Object o) in every single one of them.

Is there a way create some sort of universal method that could compare any of the two objects that I pass to it and let me know if they match in every single variable or not?

Answer 1

You have a few options for automating Equals & Hashcode (option #3 BLEW MY MIND!):

1. Your IDE. I would not recommend it for most objects as they can slowly drift out of date with the actual class definition. They also look ugly and pollute your codebase with boilerplate code.
2. Apache Commons has a bunch of stuff for making this easier, including a reflective version so no risk of drifting out of date with the class definition. It is better than #1 unless you require a speedy equals/hashcode, but still too much boilerplate for my liking.
3. Project Lombok and annotation processing. Whack an EqualsAndHashCode annotation on ya class and be done with it. I recommend using Project Lombok. It adds a touch of magic into the build (but not much) and so requires a plugin for your IDE to behave nicely but they are a small price to pay for no boilerplate code. Lombok is an annotation processor that run at compile time so you have no runtime performance hit.
4. Using a different language that supports it out the box, but also targets the JVM. Groovy uses an annotation and Kotlin supports data classes. Unless your existing code can quickly be converted, I would avoid this.
5. Google's Auto has an AutoValue. Like Project Lombok this is an annotation processor, however has less magic at the expense of little more boilerplate (thanks to Louis Wasserman)

Answer 2

you can use :

 org.apache.commons.lang.builder.CompareToBuilder.reflectionCompare(Object lhs, Object rhs); 

it uses reflection to compare the fileds here is the javadoc : javadoc