COMP 155: Object Oriented Programming Overview

Package

Mechanism for organizing class namespaces in Java.

Declaring Package

Use 'package pkg' to define a package.

File System Directories

Packages stored in directories matching their names.

Package Syntax

Form: package pkg1[.pkg2[.pkg3]].

Import Statement

Allows access to classes from other packages.

Omitting Import Statement

Classes can be used with full package names.

Access Protection

Controls visibility of classes and members.

Public Access Modifier

Members accessible from any class.

Private Access Modifier

Members inaccessible outside their class.

Default Access Modifier

Visible to subclasses and same package classes.

Protected Access Modifier

Visible to subclasses and same package classes.

Class Declaration

Defines access levels for classes in Java.

Non-Nested Class

Only has public and default access levels.

Single Public Class

Only one public class per '.java' file.

Nested Class

Can be private or protected.

I/O Streams

Abstractions for input and output operations.

Stream

Abstraction that produces or consumes information.

Physical Device

Stream linked to devices via Java I/O system.

Byte Stream

Handles binary data in Java.

Character Stream

Handles character data in Java.

Java I/O Package

Contains classes for input and output operations.

Accessibility of Members

Determines how class members can be accessed.

Hierarchy of Packages

Packages can be nested using '.' notation.

Stream

Java's method for handling input and output.

Byte Stream

Handles input/output of bytes, e.g., binary data.

Character Stream

Handles input/output of characters, supports Unicode.

InputStream

Abstract class for reading byte streams.

OutputStream

Abstract class for writing byte streams.

Reader

Abstract class for reading character streams.

Writer

Abstract class for writing character streams.

System

Encapsulates aspects of Java's run-time environment.

System.in

Standard input stream, defaults to keyboard.

System.out

Standard output stream, defaults to console.

System.err

Standard error stream, defaults to console.

PrintStream

Class for writing output to byte streams.

BufferedReader

Reads text from character input stream efficiently.

InputStreamReader

Converts byte streams to character streams.

read() method

Reads a single character from input.

readLine() method

Reads a line of text from input.

write() method

Writes bytes to output stream.

Buffered Input Stream

Supports efficient reading of characters.

Internationalization

Adapting software for different languages and regions.

Console Input

Input from the user via the console.

Console Output

Output displayed to the user via the console.

Low-level method

Basic method for writing data to streams.

Character-based stream

Stream designed for handling characters efficiently.

PrintWriter

Character-based class for console output.

flushingOn

Controls automatic flushing of output stream.

PrintWriter constructor

PrintWriter(OutputStream, boolean) initializes output stream.

toString() method

Converts object to string for display.

File I/O

Reading and writing data to files.

Byte streams

Handles raw binary data in files.

Character streams

Handles character data in files.

BufferedOutputStream

Buffers output for improved performance.

flush() method

Flushes buffered content to the output stream.

Serialization

Converts object state to byte stream.

Deserialization

Converts byte stream back to object.

Serializable interface

Marks classes for serialization support.

FileInputStream

Reads bytes from a file.

FileOutputStream

Writes bytes to a file.

FileReader

Reads characters from a file.

FileWriter

Writes characters to a file.

BufferedOutputStreamExample

Example class demonstrating buffered output.

try-finally block

Ensures resources are closed after use.

int c

Variable for reading single bytes/characters.

System.out

Standard output stream in Java.

PrintWriter methods

Includes print() and println() for output.

Serializable

Interface allowing object serialization in Java.

ObjectOutputStream

Writes objects to an output stream.

ObjectInputStream

Reads objects from an input stream.

Down-casting

Casting a superclass reference to a subclass.

Generics

Parameterized types for type-safe programming.

Type safety

Ensures data types are correctly used.

Autoboxing

Automatic conversion between primitive types and wrapper classes.

Wrapper classes

Classes that encapsulate primitive data types.

NonGen

Class demonstrating non-generic object handling.

Explicit casting

Manually converting one type to another.

Bounded Types

Restricts types used in generics to subclasses.

Stats class

Generic class for statistical calculations.

Average method

Calculates average of numeric array elements.

Upper Bound

Wildcard allowing subclasses of a specified class.

Lower Bound

Wildcard allowing superclasses of a specified class.

Generic Methods

Methods that operate on generic types.

JDK 5

Java Development Kit version introducing generics.

Type parameter

Specifies data type for generics.

Compile-time error

Error detected during code compilation.

Run-time error

Error occurring during program execution.

Generic class syntax

class ClassName.

Multiple bounds

Combining multiple constraints in generics.

Generic Method

A method that can operate on various types.

Type Inference

Compiler determines generic type parameters automatically.

Diamond Operator

<> used for type inference in generics.

ArrayList

Resizable array implementation in Java collections.

Wrapper Class

Object representation of primitive data types.

Fixed-size Array

Array with a set number of elements.

Element Index

Zero-based position of an element in an array.

Array Length

Total number of elements in an array.

List Abstraction

Dynamic collection that resizes as needed.

Generic Type

Type parameter used in class or method definitions.

ArrayList Methods

Functions for manipulating ArrayList objects.