This question already has answers here:
Global variables in Java
(25 answers)
Closed 6 years ago.
I need to have certain info inside my program which I need to access and modify in between different classes inside different packages. I've tried using a separate class for them but it doesn't work because I need to make a new instance every time I use it in a different class.
Is there a way to solve this problem?
public class ClassName {
public static String varName = "this can be used globally;"
}
Now can be referenced globally by
ClassName.varName
Note: public is important since a private will not be accessible from the outside the class.
Related
This question already has answers here:
Are static variables inherited
(4 answers)
Closed 6 months ago.
Recently, I was trying to use interfaces to store some information which I needed to use globally. Initially, I was going to make every class which needed the information implement this interface to access the data. However, I eventually realized the enormously better solution of using the fact that variables are final and static to just get the data from a static call.
Through this journey I now have a question. When a class implements an interface with variables, does each class independently store the variables in new memory, or does it just get stored once in the interface. Kind of a weird question which I couldn't find an answer to.
Static fields are stored once within their class or interface, they are not duplicated in every instance
This question already has answers here:
What is a class literal in Java?
(10 answers)
What is reflection and why is it useful?
(23 answers)
Method to dynamically load java class files
(3 answers)
Closed 1 year ago.
I've been trying to understand that how the Class Class actually works in java but everywhere I look all it says is that its references represent the Classes and Interfaces in a running java application but nowhere I've managed to find that how actually it does that? Does it store the name of the Classes as a String property? or is it something else? Also I've seen in Spring applications we pass SpringApplication.run(SomeClass.class, args) and all people say that we are passing it because because we need to pass the name of class, If it so then why can't we just pass it as a String like this SpringApplication.run("Name of that class", args)? And what is the advantage of getting the object of Class Class for a certain Class or Interface?
This question already has answers here:
What is the difference between public, protected, package-private and private in Java?
(30 answers)
Closed 5 years ago.
I know this might be thought of as a duplicate question, but I think my question is a bit different from the previous questions.
The difference between public and protected members is that a public member acts as a protected member on in that it can be accessed from the world but a protected member cannot.
What does the term world mean? Does it mean from outside the class? If so how?
Is it by using the class name? Or they can be accessed by using the variable/method name directly without the current class being a subclass?
Okay, the word "world" means that it can be accessed from anywhere inside the project (no matter if they are in the same package). However the protected members means that they can only be accessed from other classes inside the same package. Sources
This question already has answers here:
Immutable class?
(14 answers)
Closed 5 years ago.
I am wondering how would I ensure that when an instance has been created that it is then impossible to change whatever is being passed through that instance. Therefore data can only can be created once.
I have a class with get and set methods of an accountNo and SortCode, how would I ensure that when this instance is called within a main method, then it can't be changed afterwords.
Thanks
Make the fields final.
final int accountNo;
you need a strategy defining your objects Immutable
how:
declare members as final
don't provide setters
don't let subclass to override methods
check the Immutable RGB example here
This question already has answers here:
What is the difference between public, protected, package-private and private in Java?
(30 answers)
Closed 7 years ago.
I am new to java. Can anyone please tell me best way to access private method variables in another class. Thank u
Private variables are private for a reason- you're not supposed to be able to access them directly. Many classes do have getter methods though which allow you to access private variables but not change them. If you need to access private variables in your program, you need to rethink your design.