For enterprise applications, it's very layered. You have the Controller layer, the Service layer, and the DAO layer to name a few. Heavy use of interfaces and REST APIs. Enterprise applications are usually built on a framework (eg. Spring), whether it's Java or any other language. Dependencies are managed with something like Maven. Applications are run on multiple servers using a load balancer to improve performance. More on reddit.com

Nothing comes close to guava in quality. More on reddit.com

Why not just ask here what you're having trouble with? Let's have a crack, shall we? This is a class: public class Demo { } There is nothing in it (well, there is... it actually looks like this) public class Demo { public Demo(){ super(); } } Which is to say that in Java, when you write the Demo code I initially wrote, the compiler sneakily makes a method called Demo, with a method call of super(). It won't do this if you make your own constructor, but let's not focus on that - let's ask why the compiler would be so sneaky. A class is a blueprint in java, but it's not very useful on it's own - it needs to be "instantiated". In the same way that a factory might have a blueprint for a tank. Blueprints for tanks aren't very useful on their own - ask the Polish military during WW2 about how that panned out*. What is useful is a tank - but note you cannot make a tank without a blueprint. Ok, so if a class is the blueprint, what is, to continue the analogy, the outcome of the blueprint? Well, that's called an object. An object is to a class, as a tank is to a blueprint. Now in the factory, you make a tank by turning the machine on. In java, it's a little different - each class has it's own "on" switch. It would be better to think of the analogy as a spell in a spell book. The spell in written form isn't going to blow up a house. But incant the spell and kaboom! So a class is like a spell - abracadabra. And an object is the bolt of lightning that jumps forth. Which is all a long way of saying that the sneaky code Java adds is like when you read the spell. In fact, that code is a method, and a particular method - it's called a constructor. So now we have the constructor, (which is a method) and the end result is an object (which is a class made "real"). A useful class will define things - it's state. Like this: class Person { int age; } (Yes, java will also add a constructor, identical to the earlier one, but this one will be called "Person"). When you want to make this Person "real" you call that constructor. But how? You use the "new" method. So you would write Person peter = new Person(); Now you have made a Person. Saying "new Person()" is like reading the incantation. The... magic that makes that into an object is in the constructor that Java adds. If Person then has another method called, uh, "sayHello()" then you would call it like this: peter.sayHello(); //good boy Peter! Is this... useful? *I don't actually know if that story about the Polish with the cardboard tanks is real or not, one images it was grossly exaggerated. But it's a nice teaching image, right? More on reddit.com

Look at the source code of some of the apache projects like apache commons. It's source can be browsed online.

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