Xetech Software Developer Trainee Interview Questions, Process, and Tips

Typecasting is the process of converting one data type to another data type in programming.

• Typecasting is also known as type conversion.

• There are two types of typecasting: implicit and explicit.

• Implicit typecasting is done automatically by the compiler.

• Explicit typecasting is done manually by the programmer.

• Examples of typecasting include converting an integer to a float or a string to an integer.

Exceptions in Java are handled using try-catch blocks.

• Exceptions are thrown when an error occurs during runtime.

• The try block contains the code that may throw an exception.

• The catch block catches the exception and handles it.

• Multiple catch blocks can be used to handle different types of exceptions.

• The finally block is executed regardless of whether an exception is thrown or not.

OOPS principles are the basic concepts of Object-Oriented Programming that help in designing and implementing software solutions.

• Abstraction - hiding implementation details

• Encapsulation - binding data and functions together

• Inheritance - reusing code and creating new classes from existing ones

• Polymorphism - using a single interface to represent multiple types

• Composition - combining objects to create more complex ones

Java doesn't support multiple inheritance to avoid the diamond problem.

• Java supports multiple interface inheritance.

• Diamond problem occurs when two superclasses have a common method.

• Java uses interfaces to achieve multiple inheritance.

• C++ supports multiple inheritance but requires virtual inheritance to avoid the diamond problem.

Java program compiles into bytecode which is executed by JVM.

• Java code is written in .java files

• Compiler converts .java files into .class files containing bytecode

• JVM executes the bytecode

• JVM provides platform independence

• Java programs can be run on any platform with JVM installed

Objects get memory in Java from the heap memory.

• Java uses heap memory to allocate memory to objects.

• The heap memory is managed by the JVM.

• Objects are created using the 'new' keyword.

• The memory allocated to an object is released by the garbage collector when it is no longer in use.

A reference variable in Java is a variable that holds the memory address of an object.

• Reference variables are used to access the methods and properties of an object.

• They are declared using the class name followed by the variable name.

• They can be assigned null or an object of the declared class or its subclasses.

• They are passed by value, but the value is the memory address of the object.

• Example: String str = new String(

Yes, we can keep the reference variable of a parent class in the object of a child class.

• This is possible because a child class is a type of parent class and can inherit its properties and methods.

• This allows for polymorphism, where a parent class reference variable can refer to an object of a child class.

• For example, if we have a parent class Animal and a child class Dog, we can create an object of Dog and assign it t

Upcasting is converting a derived class object to its base class type. Downcasting is the opposite.

• Upcasting is safe and implicit

• Downcasting is explicit and may cause runtime errors

• Upcasting can be used for polymorphism

• Downcasting is used to access derived class specific members

• Example: Animal a = new Dog(); // upcasting

• Example: Dog d = (Dog) a; // downcasting