Java Basics for Grade 13 Students

Explain the concept of variables in Java.

• Variables in Java are used for storing images

• Variables in Java are not necessary for programming

• Variables in Java are only used for mathematical calculations

• Variables in Java are containers for storing data values with specific data types, allowing for data manipulation and storage within a program.

What is a class in Java and how is it different from an object?

• A class in Java is a function, while an object is a library

• A class in Java is a variable, while an object is a loop

• A class in Java is a data type, while an object is a method

• A class in Java is a blueprint for creating objects, while an object is an instance of a class.

How do you create an object in Java?

• new ClassName obj = ClassName();

• ClassName obj = new ClassName();

• ClassName obj = ClassName.new();

• ClassName obj = ClassName();

What are the main features of Java programming language?

• Low-level language

• Interpreted language

• Functional programming

• Platform independence, Object-oriented, Robust, Secure, Multithreaded, High performance

• Dynamic typing

What is the difference between primitive data types and non-primitive data types in Java?

• Primitive data types are mutable, while non-primitive data types are immutable.

• Primitive data types are always passed by reference, while non-primitive data types are always passed by value.

• Primitive data types can be extended, while non-primitive data types cannot.

• Primitive data types are predefined by the language and have a fixed size, while non-primitive data types are created by the programmer and can vary in size.

Explain the concept of inheritance in Java.

• Inheritance in Java does not support the 'is-a' relationship between classes.

• Inheritance in Java is a process of acquiring properties from a subclass to a superclass.

• Inheritance in Java allows a subclass to inherit properties and behaviors from a superclass, promoting code reusability and establishing an 'is-a' relationship between classes.

• Inheritance in Java is limited to only one level of hierarchy.

What is the purpose of constructors in Java classes?

• To create new instances of classes

• To initialize objects and set initial values for object attributes.

• To perform mathematical operations on objects

• To handle user input in objects

How do you declare a variable in Java?

• int num = 0;

• create new variable num;

• declare num as integer

• int num;

What is the significance of the 'static' keyword in Java?

• The 'static' keyword in Java is used to declare a member that belongs to instances of the class.

• Using 'static' in Java allows for dynamic memory allocation.

• The 'static' keyword in Java is used to define abstract classes.

• The 'static' keyword in Java is used to declare a member that belongs to the class itself rather than to instances of the class.

What is the purpose of the 'this' keyword in Java?

• The 'this' keyword is used to refer to the current instance of the class, allowing access to instance variables and methods.

• The 'this' keyword is used to create a new instance of a class.

• The 'this' keyword is used to define static methods in Java.

• The 'this' keyword is used to handle exceptions in Java.