Java Programming: Multithreading, Applets, Event Handling, I/O, AWT & Swing

Vocabulary flashcards covering key Java terms on multithreading, applets, event handling, I/O streams, AWT, graphics, and Swing GUI programming.

Multithreading (Java)

Technique of executing multiple threads simultaneously within a single program.

Thread

Lightweight sub-process; the smallest unit of CPU scheduling in Java.

Shared Memory Advantage

Threads share a common memory area, saving memory compared to separate processes.

Responsiveness Advantage

Independent threads keep the UI from blocking, allowing concurrent operations.

Thread State: New

Thread has been created but start() has not yet been called.

Thread State: Runnable

Thread is ready to run and waiting for CPU time.

Thread State: Running

Thread scheduler has picked the thread and it is executing.

Thread State: Blocked / Non-Runnable

Thread is alive but waiting for I/O, sleep, or monitor lock.

Thread State: Terminated

Thread has completed execution or exited due to an error.

Creating a Thread by Extending Thread

Subclass Thread and override run() to define task logic.

Creating a Thread by Implementing Runnable

Implement Runnable’s run() and pass instance to new Thread().

Thread Class

java.lang.Thread extends Object and implements Runnable, providing constructors & control methods.

start()

Thread method that creates a new call stack and invokes run() asynchronously.

run()

Contains the code executed by the thread when scheduled.

sleep(long ms)

Static Thread method that pauses current thread for specified milliseconds.

join()

Causes calling thread to wait until the target thread dies (optionally with timeout).

Thread Priority

Integer value (1-10) influencing scheduling order; default 5 (NORM_PRIORITY).

MIN_PRIORITY

Constant 1 — lowest thread priority.

NORM_PRIORITY

Constant 5 — default thread priority.

MAX_PRIORITY

Constant 10 — highest thread priority.

Synchronized Method

Method preceded by synchronized keyword that acquires object lock for exclusive access.

Daemon Thread

Background service thread marked by setDaemon(true); JVM exits when only daemons remain.

Runnable Interface

Functional interface with single void run() used to define thread tasks.

Multithreading vs. Multiprocessing

Threads share memory & have faster context switch; processes have separate memory.

Applet

Java program (bytecode + HTML) that runs inside a browser or appletviewer.

Applet Advantage

Adds dynamic, interactive content (e.g., games, animations) to web pages.

Applet Restriction

Runs in sandbox as untrusted code with limited system access.

Applet vs. Application

Applets lack main(); applications launch with main(String[]).

init()

Applet life-cycle method called once for initialization.

start()

Applet method called after init() and when applet gains focus.

stop()

Called when applet loses focus; used to suspend activity & release resources.

destroy()

Called once when applet is removed from memory for final cleanup.

paint(Graphics g)

Method that renders applet content; called whenever window needs redrawing.

Tag

HTML element specifying CODE, WIDTH, HEIGHT (and others) to embed an applet.

Tag

HTML element inside APPLET that passes name/value pairs to an applet.

getParameter(String)

Applet method retrieving a parameter value supplied by PARAM tag.

Local Applet

Applet stored and loaded from the client’s local system; no Internet required.

Remote Applet

Applet downloaded from a server via URL specified by CODEBASE attribute.

Delegation Event Model

Java’s event-handling scheme where sources fire events to registered listeners.

Event Source

Object that generates an event when its internal state changes.

Event Listener

Object that implements listener interface methods to process events from sources.

addTypeListener()

Source method used to register a listener for a specific event type.

EventObject

Superclass of all event classes; provides getSource() and toString().

ActionEvent

Event generated when a button is pressed, menu item selected, etc.

MouseEvent

Event generated for mouse actions (clicked, pressed, moved, etc.).

KeyEvent

Event representing keyboard input; types: KEYPRESSED, KEYRELEASED, KEY_TYPED.

WindowEvent

Event for window state changes (opened, closing, iconified, etc.).

ActionListener

Interface with void actionPerformed(ActionEvent) to handle action events.

ItemListener

Interface with void itemStateChanged(ItemEvent) for checkbox/choice changes.

KeyListener

Interface with keyPressed, keyReleased, keyTyped methods to process keystrokes.

MouseListener

Interface with mouseClicked, mouseEntered, mouseExited, mousePressed, mouseReleased.

MouseMotionListener

Interface with mouseDragged and mouseMoved methods.

TextListener

Interface with textChanged(TextEvent) for text field/area updates.

Stream (Java I/O)

Sequence of data used for input or output operations.

Byte Stream

8-bit oriented I/O classes such as FileInputStream and FileOutputStream.

Character Stream

16-bit Unicode I/O classes such as FileReader and FileWriter.

FileInputStream

Reads raw bytes from a file; returns ‑1 when end of file reached.

FileOutputStream

Writes raw bytes to a file; often used to create text or binary files.

FileReader

Character stream class that reads two bytes at a time from a file.

FileWriter

Character stream class that writes two-byte Unicode characters to a file.

DataInputStream

Input stream that lets programs read primitive Java data types from System.in or files.

PrintStream

Subclass of FilterOutputStream; System.out is a PrintStream for console output.

AWT (Abstract Window Toolkit)

Platform-dependent GUI API providing heavyweight components built on native peers.

Container

AWT component that can hold other components (e.g., Panel, Frame, Dialog).

Frame

Top-level AWT window with title bar, borders, and optional menu bar.

Panel

Generic lightweight container without title bar used to group components.

FlowLayout

Layout manager placing components left-to-right, top-to-bottom like text flow.

GridLayout

Layout manager arranging components in equal-size rows and columns.

BorderLayout

Layout manager dividing container into North, South, East, West, Center regions.

Label (AWT)

Passive text display component created with new Label(String).

Button (AWT)

Clickable component generating ActionEvent; created with new Button("OK").

Checkbox

Toggle component indicating on/off state; generates ItemEvent.

CheckboxGroup

Class used to create mutually exclusive checkboxes (radio buttons).

Choice

Drop-down pop-up list allowing single selection.

List (AWT)

Scrolling list box that can allow single or multiple selections.

Scrollbar

Component for selecting continuous values; oriented horizontal or vertical.

drawLine()

Graphics method drawLine(int x1,int y1,int x2,int y2) to render a line.

drawRect()/fillRect()

Graphics methods to outline or fill rectangles.

drawOval()/fillOval()

Graphics methods to outline or fill ellipses/circles.

drawArc()/fillArc()

Graphics methods to render arcs defined by start and sweep angles.

drawPolygon()/fillPolygon()

Graphics methods to outline or fill multi-sided shapes defined by point arrays.

Swing

Lightweight, platform-independent GUI toolkit in javax.swing built atop AWT.

Lightweight Component

Component implemented in Java without native peer, reducing platform dependence.

Pluggable Look and Feel

Swing feature that lets applications change GUI theme at runtime.

AbstractButton

Superclass for Swing buttons providing common behavior (icons, text, action events).

JButton

Swing push button supporting text, icons, or both.

ImageIcon

Class that encapsulates images used in Swing components.

AWT vs Swing: Platform Dependency

AWT components are heavyweight & platform-dependent; Swing components are lightweight & platform-independent.

Heavyweight Component

GUI element that relies on an underlying native peer (e.g., Frame, Dialog).