How Is This Private Variable Accessible

How is this private variable accessible?

A private member is accessible from any method within the class in which it is declared, regardless of whether that method accesses its own (this) instance's private member or some other instance's private member.

This is stated in JLS 6.6.1:

...Otherwise, if the member or constructor is declared private, then access is permitted if and only if it occurs within the body of the top level class (§7.6) that encloses the declaration of the member or constructor.

This feature of Java allows you to write methods that accept an instance of the class as an argument (for example - clone(Object other), compareTo(Object other)) without relying on the class having non private getters for all the private properties that need to be accessed.

private member variable is accessed by another object of same class?

you are not accessing c.value outside of the c object.

What you are doing is accessing a private variable of a class in the same class. Because the c variable is of exactly the same type as the class, you can access private variable c.value in that class.

Imagine the following situation

public class HelloWorld 
{
    public static void main(String[] args)
    {
        OtherClass myObject = new OtherClass(7);
        OtherClass yourObject = new OtherClass(4);
        yourObject.value = 23;
        System.out.print(myObject.compareTo(yourObject));
    }
}

public class OtherClass
{
    private int value;
    OtherClass(int value) 
    {
        this.value = value; 
    }  

    public int compareTo(OtherClass c) 
    {
        return this.value - c.value;
    }  
}

Your code would not compile because value is not accessible from any class other than OtherClass. However, if you try to access c.value you will certainly succeed in doing that.

You would understand better if you study encapsulation more, and a good source of information is the [official documentation](https://docs.oracle.com/javase/tutorial/java/concepts/object.html"Oracle Documentation")

Angular2 - should private variables be accessible in the template?

UPD

Since Angular 14, it is possible to bind protected components members in the template. This should partially address the concern of exposing internal state (which should only be accessible to the template) as the component's public API.

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No, you shouldn't be using private variables in your templates.

While I like the drewmoore's answer and see perfect conceptual logic in it, implementationwise it's wrong. Templates do not exist within component classes, but outside of them. Take a look at this repo for the proof.

The only reason why it works is because TypeScript's private keyword doesn't really make member private. Just-in-Time compilation happens in a browser at runtime and JS doesn't have any concept of private members (yet?). Credit goes to Sander Elias for putting me on the right track.

With ngc and Ahead-of-Time compilation, you'll get errors if you try accessing private members of the component from template. Clone demonstration repo, change MyComponent members' visibility to private and you will get compilation errors, when running ngc. Here is also answer specific for Ahead-of-Time compilation.

Why private variable declared outside the class can be access Class on the same file?

private is intended for use inside a type declaration. Otherwise it has no meaning. When private is used in a place where it has no meaning, it is reinterpreted as fileprivate. That is what happens here. This code is in the same file so the fileprivate variable is visible.

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