CS110: Programming Language I - Lecture 2: Java Basics 1

Vocabulary practice flashcards covering fundamental concepts, syntax, data types, identifiers, variables, constants, type casting, and output formatting from CS110 Lecture 2: Java Basics 1.

.java

The file extension required for storing all Java source code programs.

Java Bytecode (.class file)

The intermediate executable file generated by the Java Compiler from source code, which is executed by the Java Virtual Machine (JVM).

Java Virtual Machine (JVM)

The software component that executes compiled Java bytecode (.class files) alongside library code to run the application and display output.

Java Compilation and Execution Process

The sequence in which a Java source code file (.java) is compiled by the Java Compiler into bytecode (.class), which is subsequently executed by the JVM alongside library code to display results on the console.

Class

A primary construct in Java where every program must contain at least one; by convention, class names start with an uppercase letter.

main Method

The entry and starting point of execution for every Java application, defined specifically as public static void main(String[] args).

Statement

A command or instruction representing an action or sequence of actions in Java; every statement must terminate with a semicolon (;).

Block

A program structure formed by a pair of braces ({ }) that groups together related components and statements.

Comment

Non-executable text ignored by the compiler, used to document programs and enhance readability. Includes single-line comments (//) and multi-line comments (/* */).

Reserved Words (Keywords)

Words that possess a defined, specific meaning to the Java compiler, always spelled in lowercase letters and prohibited from being used as identifiers (e.g., class, public, static, void).

Whitespace

Any spacing in code without executable statements—such as spaces between words, blank lines, and indentation—that keeps code organized without affecting how it runs.

System.out.println()

A printing method that outputs a given String and automatically advances the cursor to the beginning of the next line; it can execute without arguments.

System.out.print()

A printing method that outputs text while leaving the cursor on the same line; it requires arguments, otherwise a syntax error occurs.

Escape Sequence

A character preceded by a backslash () that conveys a specialized formatting instruction to the compiler (e.g., \n for new line, \t for tab, \" for double quotes).

Identifier

A sequence of characters consisting only of letters, digits, underscores (_), and dollar signs ($) used to name classes, methods, or variables; it cannot start with a digit, contain spaces, or match a reserved keyword.

Case Sensitivity

The rule in Java specifying that uppercase and lowercase letters are treated as distinct, making names such as a1 and A1 completely different identifiers.

Variable

A named container allocated in memory for holding changeable data values of a specified type.

Initialization

The act of assigning an initial value to a variable, either simultaneously during declaration or in a subsequent statement prior to use.

String Concatenation

An operation using the plus (+) operator to join multiple strings, characters, or numerical values together into a single unified String.

Constant

An identifier declared with the reserved word final that holds a permanent, unchangeable value throughout the program's execution (e.g., final double PI = 3.14159265;).

Type Casting

The conversion of a value from one data type to another; it can be implicit (automatic) or explicit (syntax-driven, where fractional parts of floating-point numbers are truncated).

System.out.printf()

A formatted printing method that outputs data based on a format string containing fixed text and format specifiers, paired with a comma-separated list of items.

Format Specifier

A placeholder in a printf format string beginning with a percent sign (%) that dictates how an argument value is rendered (e.g., %d for integers, %f for floating-point, %s for String).

byte Data Type

An integer primitive type with a size of $8\text{ bits}$, holding values from $-128$ ($-2^{7}$) to $+127$ ($2^{7} - 1$).

short Data Type

An integer primitive type with a size of $16\text{ bits}$, holding values from $-32,768$ ($-2^{15}$) to $+32,767$ ($2^{15} - 1$).

int Data Type

An integer primitive type with a size of $32\text{ bits}$, holding values from $-2,147,483,648$ ($-2^{31}$) to $+2,147,483,648$ ($2^{31} - 1$).

long Data Type

An integer primitive type with a size of $64\text{ bits}$, holding values from $-9,223,372,036,854,775,808$ ($-2^{63}$) to $+9,223,372,036,854,775,808$ ($2^{63} - 1$).

float Data Type

A single-precision floating-point primitive type with a size of $32\text{ bits}$, holding values from $-3.4 \times 10^{38}$ to $+3.4 \times 10^{38}$ with up to $7$ significant digits after the decimal point.

double Data Type

A double-precision floating-point primitive type with a size of $64\text{ bits}$, holding values from $-1.7 \times 10^{308}$ to $+1.7 \times 10^{308}$ with up to $15$ significant digits after the decimal point.

boolean Data Type

A $1\text{-bit}$ primitive data type used to evaluate and store logical states consisting strictly of true or false.

char Data Type

A $16\text{-bit}$ primitive data type that stores the Unicode of a single character enclosed in single quotes, ranging in value from $0$ to $65,535$ ($2^{16} - 1$).