What is constant and variable in Java?
What is constant and variable in Java?
A constant is a value that cannot be altered by the program during normal execution, i.e., the value is constant. This is contrasted with a variable, which is an identifier with a value that can be changed during normal execution, i.e., the value is variable.
What is constants in Java?
A constant is a variable whose value cannot change once it has been assigned. Java doesn’t have built-in support for constants. A constant can make our program more easily read and understood by others. To define a variable as a constant, we just need to add the keyword “final” in front of the variable declaration.
How do we declare constants in Java?
To make any variable a constant, we must use ‘static’ and ‘final’ modifiers in the following manner: Syntax to assign a constant value in java: static final datatype identifier_name = constant; The static modifier causes the variable to be available without an instance of it’s defining class being loaded.
How do you declare a final variable in Java?
There are three ways to initialize a final variable :
- You can initialize a final variable when it is declared. This approach is the most common.
- A blank final variable can be initialized inside instance-initializer block or inside constructor.
- A blank final static variable can be initialized inside static block.
Can we initialize final variable in constructor?
A final variable must be initialized at the declaration or in a constructor. A final variable can only be initialized once, either via an initializer or an assignment statement. It does not need to be initialized at the point of declaration: this is called a “blank final” variable.
What is the final variable?
Once a final variable has been assigned, it always contains the same value. If a final variable holds a reference to an object, then the state of the object may be changed by operations on the object, but the variable will always refer to the same object (this property of final is called non-transitivity).
Can we override the static method?
Can we Override static methods in java? We can declare static methods with the same signature in the subclass, but it is not considered overriding as there won’t be any run-time polymorphism. Hence the answer is ‘No’.
Can we declare constructor as private?
Yes, we can declare a constructor as private. If we declare a constructor as private we are not able to create an object of a class. We can use this private constructor in the Singleton Design Pattern.
Can constructor be overridden?
Constructor looks like method but it is not. It does not have a return type and its name is same as the class name. But, a constructor cannot be overridden. If you try to write a super class’s constructor in the sub class compiler treats it as a method and expects a return type and generates a compile time error.
Can we override private methods?
No, we cannot override private or static methods in Java. Private methods in Java are not visible to any other class which limits their scope to the class in which they are declared.
Why constructor is always public?
No, Constructors can be public , private , protected or default (no access modifier at all). Making something private doesn’t mean nobody can access it. It just means that nobody outside the class can access it. Using private constructor we can ensure that no more than one object can be created at a time.
Is constructor public by default?
Implicitly-declared default constructor If no user-declared constructors of any kind are provided for a class type (struct, class, or union), the compiler will always declare a default constructor as an inline public member of its class.