A java programming question and answer is an important part of technical interviews. It can be difficult to answer, but it's worth practicing. Here are some tips to help you prepare for these questions. A variable can be either static or local, but not both. Defining it as static causes compilation error.
Variables
A variable in java is a container for storing values. It has a name, a type, and an initial value. A variable can be modified using a statement that includes its name, an equals sign, and the new value. When naming variables, it is important to use camel case. For example, javaIsCool and javaiscool are two different variables.
Variables in java are stored in stack and heap memory. Stack memory is fixed, while heap memory is dynamic. Variables in java are strongly typed. Their type is determined at the time of declaration and doesn’t change at runtime. For example, a string will remain a string and a number will remain a number. It is a good practice to initialize all variables at the time of declaration. This will avoid unexpected behavior and errors. In addition, it will reduce the number of lines of code. Besides, it will increase the performance of the program. You can read more about java programming here.
Classes
A class is a template from which objects are created. It contains fields and methods for storing data and providing functionality. Classes are a key part of object-oriented programming, and Java uses classes extensively.
Each class has a constructor, which creates an instance of that class when it is first invoked. The constructor is a block of code that initializes the new object by allocating memory. Every class must have a constructor, either a default one provided by the compiler or a new one written for the class.
A class may use various access modifiers such as public (a method that can be called from any other class) and private (a method that can only be accessed in its own class). The class name is used as the name of the class file and has.java appended. A class can also be declared as final, which means its value can’t be changed. This is useful for debugging purposes.
Methods
Methods in java are chunks of code that do specific jobs. They are set out in a particular way – a header, followed by the method body. The header tells java programming question and answer what value the method will return (an int, a double, a string) and also what parameters it will accept. These are then enclosed between a pair of round brackets.
Local variables declared inside a method have method level scope and cannot be accessed outside of it. Methods can be static or non-static. Non-static methods require an object of that class to be created in order to call them.
Static methods are important in java as it reduces the memory consumption by storing code once and running it multiple times in the same process. This also improves the performance of a program as the same code is being executed multiple times in the same runtime. Methods can also be grouped into categories like math functions - sqrt(), log(), min(), max() etc and string function - charAt(str), substring(), replace() etc.
Objects
Objects are one of the most important concepts in java programming. Objects are real-world entities that have a unique identity and exhibit behavior. These objects can be both physical (e.g., a pen) and logical (e.g., an airline system or a banking system). Objects can have different states and behaviors.
A class is the blueprint for an object. A class contains all the variables and methods that an object will have. The class is then instantiated, and the instance of the object is created on the heap.
An instance of a class is called a reference variable. A reference variable can refer to any object of the same type as it is declared. This makes it easy to pass data from one object to another. The super keyword is used to refer parent class objects. The subclass inherits the variables and methods from its super class. This gives the subclass access to all the public methods and fields of its super class.
