CSG2H3 Object Oriented Programming Java I/O

Computer and Me

Input / Output Input : Keyboard File Output Screen file

Java Stream Sequence of data of undetermined length Input streams move data into a Java program usually from an external source System.in Output streams move data from a Java program to an external target. System.out

Java Stream A Java stream is composed of discrete bytes (characters) of data Byte streams Character streams

Byte Streams FileInputStream BufferedInputStream InputStream FilterInputStream DataInputStream Object FileOutputStream BufferedOutputStream OutputStream FilterOutputStream DataOutputStream PrintStream

Character Streams BufferedReader Reader InputStreamReader FileReader Object BufferedWriter writer OutputStreamWriter FileWriter PrintWriter

Snippet Code : Write String

Snippet Code : Read String

CSG2H3 Object Oriented Programming Object Persistence

Object Persistence Persistence is the property of an object through which its existence transcends time (i.e. the object continues to exist after its creator ceases to exist) and/or space (i. e. the objects location moves from the address space in which it was created).

Object Persistence the ability of an object to survive the lifetime of the OS process in which it resides relevant for objects with an internal state The state needs to be retained between object deactivation and object activation

Live-time Object Illustration Instantiation Object used in program Some-time Object Saved//Resurect into/from Storage Object destroyed

Object Oriented Live as an Object constructor Save as an Object serializing Read as an Object De-serializing

Persistence Object To File Must be able to transform to binary (implements java.io.Serializable) BinaryStream Using io.stream mechanism FileOutputStream Write Object to File Using method writeObject() in ObjectOutputStream Object in File Open file with FileInputStream class ReadObject in File Using method readObject() in ObjectInputStream Object Object ready to use

Snippet Code : Write Object

Snippet Code : Read Object

Object Relational Mapping

Object Relational Mapping a programming technique for converting data between incompatible type systems in object- oriented programming languages object-oriented (OO) objects are almost always non-scalar values However, many popular database products such as structured query language database management systems (SQL DBMS) can only store and manipulate scalar values

Object Relational Mapping The programmer must either convert the object values into groups of simpler values for storage in the database (and convert them back upon retrieval), or only use simple scalar values within the program. Object-relational mapping is used to implement the first approach

Java Hibernate

Java Persistence API (JPA)

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Credits Music : Yonezawa Madoka - Oui! Ai Kotoba (Instrumental)