Introduction to Java – Lecture Vocabulary

A vocabulary set covering the essential Java terms, components, memory areas, variable types, and literal formats discussed in the lecture.

Java

A high-level, object-oriented programming language used to build robust, platform-independent applications.

James Gosling

Co-creator of Java at Sun Microsystems in 1995.

Bill Joy

Co-creator of Java alongside James Gosling at Sun Microsystems.

Sun Microsystems

The company where Java was originally developed before being acquired by Oracle.

Oracle (Java)

Company that bought Java on January 27, 2010 and now provides major updates every six months.

OAK

The original name for Java, designed for interactive TV set-top boxes.

Write Once, Run Anywhere (WORA)

Java’s principle that compiled code can run on any platform with a JVM.

Applet

A small web-based embedded Java application.

Swing

Java’s GUI toolkit for building desktop applications.

Java Server API

A collection of Java technologies for building enterprise web applications.

Robust (Java feature)

Java’s ability to handle runtime errors and manage memory safely.

Portable

Property that allows Java programs to run on different hardware/OS without modification.

Multi-threading Support

Java’s built-in capability to run multiple threads concurrently for better performance.

Exception Handling

Java mechanism for detecting and managing runtime errors gracefully.

Collection API

Java framework of classes and interfaces for storing and manipulating groups of objects.

Java Development Kit (JDK)

Complete development environment that includes JRE, JVM, compiler (javac), libraries, and tools for building Java apps.

Java Runtime Environment (JRE)

Software package containing JVM and core libraries required to run Java programs.

Java Virtual Machine (JVM)

Abstract computing machine that loads, verifies, and executes Java bytecode on any hardware.

javac

Java compiler that converts .java source files into .class bytecode files.

Bytecode

Platform-independent instruction set produced by javac and executed by the JVM.

Just-in-Time (JIT) Compiler

JVM component that converts bytecode into native machine code during runtime for faster execution.

JShell

Java’s interactive REPL that lets developers test and run code snippets directly in a terminal.

Stack Memory (JVM)

Region storing method calls and local variables; each thread gets its own stack.

Heap Memory (JVM)

Area where objects and instance variables are allocated and garbage-collected.

Method Area / MetaSpace

JVM region holding class-level metadata, static variables, and constant pools.

PC Register

Per-thread register that holds the address of the current JVM instruction.

Native Method Stack

Memory area that manages calls to native (non-Java) methods, such as C/C++ functions.

Local Variable

Variable declared inside a method, block, or constructor; exists only during method execution; stored on the stack.

Instance Variable

Non-static variable defined inside a class but outside methods; each object has its own copy; stored on the heap.

Static Variable

Variable declared with the static keyword; shared by all instances; stored in the method area.

Final Variable

Variable declared with final whose value cannot be changed once assigned.

Literal

Fixed constant value written directly in code, such as 10 or "Hello".

Integer Literal

Whole-number constant; default type int (e.g., 42, ‑7).

Floating-Point Literal

Decimal constant; default type double unless suffixed with f/F for float (e.g., 3.14, 2.5f).

Character Literal

Single-character constant enclosed in single quotes (e.g., 'A', '\n').

String Literal

Sequence of characters enclosed in double quotes (e.g., "Java").

Boolean Literal

Logical constant true or false.

Null Literal

Special literal null denoting no reference value.

Octal Literal

Integer literal beginning with 0 representing base-8 value (e.g., 012).

Hexadecimal Literal

Integer literal beginning with 0x or 0X representing base-16 value (e.g., 0xFF).

Binary Literal

Integer literal beginning with 0b or 0B representing base-2 value (e.g., 0b1010).

Scientific Notation Literal

Floating-point literal using e/E to represent powers of ten (e.g., 1.5e2).

Underscore in Numeric Literals

Feature (Java 7+) allowing underscores to improve readability in numbers (e.g., 1000000).

Type Casting / Conversion

Process of converting one data type into another, either implicitly or explicitly in Java.

Garbage Collection

Automatic memory management process in the JVM that reclaims unused objects.

Sandbox (JVM)

Secure execution environment provided by JVM to restrict untrusted code.