Java Fundamentals Quiz

Java Fundamentals

• Java programs use comments, ignored by the compiler.
• Comments start with // (single line) or /* */ (multiple lines).
• A class header contains an access modifier (e.g., public), the class keyword, and the class name (e.g., Student).
• Curly braces {} define the scope of a class or method.

Parts of a Java Program

• Every Java application needs a main method.
• The main method executes the program.
• Java statements within the main method run sequentially when the program is executed.
• Class headers, method headers and curly braces do not end with a semicolon.
• System.out.println() is used to print output.

Console Output

• Java output is handled through the Java API (Application Programming Interface).
• The API is a prewritten library of classes for operations.
• System.out.print() will print data to the console.
• System.out.println() will print the data and move the cursor to the next line.
• System is a part of the Java API.
• println() prints data then advances the cursor to the next line.
• print() prints data without advancing the cursor.

Comments

• Comments are for human readers; the compiler ignores them.
• Comments come in single-line // and multi-line /* */.
• Javadoc comments (/** */) help document code.

Java Tokens

• Tokens are the smallest units of a Java program.
• Examples include keywords (int, double,class, public), operators (+, -), symbols ({, }), constants, and identifiers.

Special Characters

• //: Single-line comment
• (): Parentheses in method headers for parameter lists.
• {}: Curly braces to enclose code sections.
• "": Quotation marks for strings
• ;: Semicolon to end a statement.

Java Escape Sequences

• Escape sequences start with \ and specify special characters.
• \n: Newline
• \t: Tab
• \b: Backspace
• \r: Carriage return
• \\: Backslash
• \': Single quote
• \": Double quote

Identifiers

• Identifiers are names used for variables, constants, classes, and methods.
• Identifiers consist of letters, digits, underscore (_), and dollar sign ($).
• Identifiers cannot start with a digit.
• Java is case-sensitive (Number is different from number).
• Reserved keywords cannot be used as identifiers (e.g., int, class, void).

Naming Conventions

• Identifiers should be descriptive and self-documenting.
• Use lower camel case for variable names (e.g., studentName).
• Use upper camel case for class names (e.g., Student).
• Avoid run-together words. Use underscores if necessary (e.g., annual_sale).

Reserved Words (Keywords)

• Reserved words, also called keywords, have specific meanings in Java and cannot be redefined.
• Examples: int, short, float, double, char, final, void, return.

Whitespaces

• Java programs use whitespace to separate elements (e.g., words, symbols).
• Whitespace includes spaces, tabs, and newlines.
• Spaces, tabs, and newlines are used for readability.

Variables

• Variables are named memory locations whose contents can be changed.
• Variables are accessed using their names.

Variable Declaration

• Declare variables by specifying the data type and identifier.
• Example: int count;, double price;, String name;

Assignment Statement

• Variables get values using the assignment operator (=).
• Example: age = 30;

Example: Variable Initialization

• Initialize variables at declaration or later.
• Example: int age = 30; , String name = "Alice";

Example: Printing variable Value

• Print the value of variables using println().
• Example: System.out.println(age);

Credit

• Tony Gaddis's "Starting Out with Java: From Control Structures through Objects" (6th Edition)