Java: Accessing Private Variables in Client Class

[Bleys]

Hello there; I have a very short question about client class access:

Suppose in a supplier class an instance variable is declared private (and is used in the constructor), and a void method in the same class (declared public) changes this variable. In the client class, is calling this method still going to change the variable (assuming an object of that class is instantiated of course). I know if the method is called within its own class then the variable will be changed, no problem. I was wondering whether the fact it's being called outside of its class makes a difference.
Something like:

public class Auto(){
private int gas;

public Auto(){
gas = 0
}

public void addGas(int g){
gas = gas + g;
}
}

and if addGas is called somewhere outside of the class, will the gas variable still be accessed and changed?

 

[Mark44]

Hello there; I have a very short question about client class access:

Suppose in a supplier class an instance variable is declared private (and is used in the constructor), and a void method in the same class (declared public) changes this variable. In the client class, is calling this method still going to change the variable (assuming an object of that class is instantiated of course). I know if the method is called within its own class then the variable will be changed, no problem. I was wondering whether the fact it's being called outside of its class makes a difference.
Something like:

public class Auto(){
private int gas;

public Auto(){
gas = 0
}

public void addGas(int g){
gas = gas + g;
}
}

and if addGas is called somewhere outside of the class, will the gas variable still be accessed and changed?

Yes, but it will not be accessed directly. Your public method addGas will do that.

Auto car = new Auto();
car.addGas(10);

The car instance is created with its gas property initialized to 0. The next line calls the addGas method to add 10 (gallons, liters?) of gas.

 

[Bleys]

thank you, Mark!

 

[Mark44]

You're welcome!

 

[LudusRex]

I would like to clarify that the access to private variables in a client class depends on the programming language and the specific implementation of the class. In Java, private variables can only be accessed and modified within the same class they are declared in. This means that in the example given, the gas variable in the Auto class can only be accessed and changed within the Auto class itself. Any attempts to access or modify it from outside the class will result in an error.

However, there are ways to indirectly access and modify private variables in Java, such as using public methods that can change the value of the private variable. In this case, the addGas method in the Auto class can be called from a client class, and it will successfully change the value of the gas variable. This is known as encapsulation, where a class controls the access to its own variables and data.

In conclusion, in Java, private variables cannot be directly accessed or modified from a client class. However, it is possible to indirectly access and modify them through public methods within the same class. It is important to follow the principles of encapsulation and carefully control access to private variables in order to maintain the integrity and functionality of a class.