关于Java语法的一些疑问

Question

I am a beginner in Java, I know something of the basics, but sometimes I see lines of codes that I don't really understand why they are written that way, here are some questions that I have:

Question 1:

Methods or attributes that are called with other methods or attributes:

Ex.: System.out.print();

I understand that system is a class, and when you write System.out, you are calling the "out" attribute, but from the "out" attribute, you call the "print()" method, is the print() method within the out attribute? how does this works. Also sometimes I see method being called that way: ... method1().method2(); If I put a method inside the scope of another method, won't it run automattically? like:

public void method1(){ method 2};

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Question 2: I've been learning about the Date and Calendar classes, and I saw a video where the guy instantieted objects of Date and Calendar, without using the world "new", neither a construction method:

Date d = Date.from(Instant.parse("2018-06-25T15:42:07Z"));

Calendar cal = Calendar.getInstance();

How does that works? Can I instantiate any object of any class by calling a abstract method (if the class have one)? Or is just that in those methods they are returning a Date and Calendar object?

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Question 3:

How can a array of type have a the atributte "length", aren't array just a set of primitive types? how can a primitive type have attributes??

Ex: int[] x = new int[3];

System.out.print(x.length); //Prints 3;

Answer 1

Question 1:

System has a class, and it has a field (often in Java, it's called a field instead of an attribute. They are the same thing though) called out . out is of type PrintStream . You don't have to worry about what a printStream is, but just know that printStream has a method called print . So, you access System 's field called out , and you call that fields print method.

You can do stuff like method1().method2() because method1 returns an object, and you call that objects method. For example, let's say you have a class which has a method called print() . Then if you have a method like this:

public A getA() {
    return new A();
}

Then if you call that method, you will get an a class. With that a class, you can call it's method and access it's fields.

getA().print();

Question 2

Like in the previous answer, you can get objects from methods. So, you assign your object to the return value of that method. For example, if you have the same method as before:

public A getA() {
    return new A();
}

You can do:

A a = getA();

Since it returns an A type, you assign it to your A .

Question 3

Array is actually a special type. It's technically an object, which allows it to have fields like length , however you can still get elements using array[5] for example. I don't think you should worry about arrays, it is very different than regular objects.