CS2 Unit 1: Bytes and Java Basics

Questions and Answers

What is the value of one MegaByte in terms of bytes?

1 trillion bytes

1 million bytes (correct)

1 billion bytes

1 thousand bytes

Which of the following statements about Java programming is false?

Java is designed for the internet.

Java has a vast set of library packages.

Java is not case-sensitive. (correct)

Java is platform-independent.

What is the primary function of a compiler in programming?

To test and debug code applications

To format code for better readability

To translate source code into machine code (correct)

To execute source code directly

Which type of software development tool is typically more feature-rich and provides testing capabilities?

IDE Signup and view all the answers

What distinguishes source code from machine code?

Source code is human-readable and easily understandable. Signup and view all the answers

What is the role of the JVM in running Java applications?

Acts as the run-time engine to execute Java applications. Signup and view all the answers

Which of the following statements about the main method in a Java application is true?

The main method is automatically called when the program is executed. Signup and view all the answers

What is a characteristic of a class in Java?

It must match the name of the file containing it if declared public. Signup and view all the answers

How should methods be named in Java?

Names should start with a lowercase letter. Signup and view all the answers

What distinguishes an object from a class in Java?

Classes define how instances are created and behave, while objects are the actual components. Signup and view all the answers

Study Notes

Bytes & Bits

1 Byte = 8 bits
1 KiloByte (KB) = 1,000 bytes
1 MegaByte (MB) = 1,000,000 bytes
1 GigaByte (GB) = 1,000,000,000 bytes
1 TeraByte (TB) = 1,000,000,000,000 bytes

Java Programming Generalities

Java is safe, portable, and platform-independent.
Features a vast array of library packages for developers.
Designed for internet applications and utilizes object-oriented programming principles.
Follows a specific syntax; for example, System.out.println("hello world");.
Case-sensitive, meaning uppercase and lowercase letters are treated differently.

Source Code

Composed of instructions in a programming language directing computer operations.
Structured to be human-readable with functions, definitions, and operational statements.

Types of Editors

Text Editor (e.g., Notepad++) focuses primarily on code editing.
Integrated Development Environment (IDE) like Visual Studio Code has advanced features for testing and previewing code.
Prominent IDEs include IntelliJ, Eclipse, and Visual Studio Code as of 2024.

Compiler

A compiler translates source code into machine code for execution by a computer.
Class files contain bytecode and have a .class extension, utilized by the Java Virtual Machine (JVM) for running Java applications.

Main Method

Each Java application contains a class with a main method.
The main method’s instructions execute when the application starts: public static void main(String[] args) {...}.
This method is called automatically upon program execution.

Classes

Classes are the foundational building blocks of Java, acting as blueprints defining object properties and behavior.
Declared using the keyword "class" and must follow naming conventions, such as using uppercase for the first letter.
Class body is enclosed in curly braces { }.
The public class name must match the file name; e.g., HelloPrinter must be in HelloPrinter.java.
Programs can have multiple classes, but only one can be public.

Methods

Methods are sets of instructions designed to perform operations on data.
They typically begin with a lowercase letter.

Objects

Objects are instances of classes, representing actual components of programs.
An object can call methods, e.g., System.out.println("Hello World");.

Variables

Variables store values for future use and have types that must be specified when declared.
Use meaningful names and start with a lowercase letter.

Types

String: Text in double quotes " ".
int: Integer values.
float: Decimal numbers.
char: Single character in single quotes ' '.
boolean: Represents true or false values.
Arithmetic operators (+, -, *) can be used with these types.

Identifiers

Identifiers are names for packages, classes, methods, or variables.
Must start with a letter, underscore, or dollar sign; subsequent characters can include letters, numbers, or underscores.
Cannot contain symbols like ?, %, or spaces, and must adhere to camel case convention.
They are case-sensitive and cannot consist of reserved words like "class."

Class vs Method vs Objects Example

The class represents a skeleton with data and methods for data manipulation.
Objects derived from the class provide different characteristics under the same attributes.
Methods are instructions tied to the object, e.g., a method write() directing an action.
Calls to methods vary by object, like male.write() or female.write(), demonstrating method accessibility across different instances.

Description

Test your knowledge on the basics of bytes and bits as well as fundamental concepts in Java programming. This quiz covers storage units from bytes to terabytes and key features of Java. Perfect for foundational understanding in computer science.