Input and Output

computerharpySoftware and s/w Development

Dec 2, 2013 (3 years and 4 months ago)

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Input and Output

Text and Binary I/O

Chapter 19

Introduction to Java Y.Daniel Liang

1

File Input and Output

Programs to run are in the FileIO folder:



1. ScannerDriver.java



2. ScannerFile.java


ScannerTextfile.txt (input file)


ScannerOutputfile.txt (output file)



3. Inventory.java (Driver)


InventoryItem.java


input file: inventory.txt








Introduction to Java Y.Daniel Liang

2

File Input and Output

Programs to run contd.

4. TestPrint.java


5. TestPrintWriter.java Team #1


output file: pw.txt


6. TestFileStream Team #2



7. TestDataStream Team #3


output file: temp.dat






Introduction to Java Y.Daniel Liang

3

File Input and Output

Programs to run contd.


8. Copy.java Team #4



Welcome.java (source file)


Temp. java (target file)


9. TestObjectStreamForArray Team #5





Introduction to Java Y.Daniel Liang

4

Objectives



To understand how I/O is processed in Java



To distinguish between text I/O and binary


I/O



To read data from the console using the


Scanner class



To read data from a file using the Scanner


class




Introduction to Java Y.Daniel Liang

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Objectives contd.



To write data to a file using the PrintWriter


class



To read and write bytes using FileInput


Stream and FileOutputStream



To read and write primitive values and


strings using DataInputStream/


DataOutPutStream



Introduction to Java Y.Daniel Liang

6

Objectives contd.



To store and restore objects using


ObjectOutputStream and ObjectInputStream


and to understand how objects are serialized


and what kind of objects can be serialized


To use the
Serializable

interface to enable
objects to be serializable


To know how to serialize arrays







Introduction to Java Y.Daniel Liang

7






Input and Output


Introduction

Data held in variables, arrays, and objects are
temporary.

Data are lost when the program
ceases processing


To save the data created during the life of the
program, you must save the data in a file onto a
disk, CD, or some other storage device

.


Then the file can be transported and can be
read later by other programs




Introduction to Java Y.Daniel Liang

8

Introduction

Redirection of Input and Output

It is tedious to test programs by typing data in for every test run.



Testing is far easier if the program reads input from a file.


You can prepare the file once and reuse it for many tests.


The command line interfaces of most operating systems provide a way
to link a file to the input of a program, as if all the characters in the
file had actually been typed by the user .

Introduction to Java Y.Daniel Liang

9

Introduction

Redirection of Input and Output example:


java ClassName < data.txt > output.txt



Use input redirection to avoid repetitive typing during testing.

Use output redirection to save your program output in a file.

Introduction to Java Y.Daniel Liang

10

Introduction contd.




Data are stored in two basic formats:
text and binary



Text file is represented in human
-
readable form


Examples of
text files

that you can read:




Files that are created with a simple text exitor ,
such as Windows Vista NotePad, as well as Java


source code, and HTML Files



Introduction to Java Y.Daniel Liang

11

Introduction contd.




Data stored in a binary file are represented in binary
form. You cannot read binary files. The files are
designed to be read by programs.



Binary files consists of a series of bits



Text file consist of a series of characters.

Introduction to Java Y.Daniel Liang

12

Introduction contd.




The advantage
s

of binary files
are

that
:



1.

T
hey are more efficient to process than text



files. Text I/O requires encoding and decoding



whereas binary I/O does not.



2. Binary files are independent of the encoding


scheme on the host machine and thus are


portable.


Introduction to Java Y.Daniel Liang

13

Introduction to Java Y.Daniel Liang


The Scanner class


The simplest tool for reading text files is the


Scanner class.


Class


java.util.Scanner




14

Introduction to Java Y.Daniel Liang


to
Get Input from the Console Using the Scanner Class

Run
ScannerDriver

program in the FileIO Folder


next(): reading a string. A string delimeter is a space



nextByte(): reading an integer of the byte type


nextShort(): reading an integer of the short type


nextInt(): reading an integer of the int type


nextLong(): reading an integer of the long type


nextFloat(): reading a number of the float type


nextDouble(): reading number of the double type

15

Introduction to Java Y.Daniel Liang


To Get Input from a text file Using the Scanner Class


Run
ScannerFile

Program in the FileIO Folder


The action of reading data from a

file is called
file input
.





16

Introduction to Java Y.Daniel Liang






To read

text

data from a disk file, we use the
FileReader

and
BufferedReader
objects.


We first construct a FileReader object


with the name of the file


Then we associate a
BufferedReader

object to the file.



Then we read data, using the
readLine

method of the
BufferedReader class
.



Finally, we convert the
String

to a primitive data type as
necessary.


Run Programs: InventoryItem (Driver)


Inventory


Use input file: inventory.txt

17

Introduction to Java Y.Daniel Liang

Sample code for processing a text file:

String file = “customer.txt”;

String line;

try{


FileReader fr = new FileReader (file);


BufferedReader inFile = new BufferedReader(fr);



line = inFile.readLine();



while(line != null && count < MAX) {


tokenizer = new StringTokenizer(line);


name = tokenizer.nextToken();




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Introduction to Java Y.Daniel Liang

Cont’d.

try{


custNumber = Long.parseLong (tokenizer.


nextToken());


balance = Double.parseDouble(tokenizer.


nextToken());


phone = tokenizer.nextToken();


custsArray[count++] = new Customer(name,


custNumber, balance, phone);


} // end inner try block


catch (NumberFormatException e) { }


line = inFile.readLine();


}// end while block


inFile.close();

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Introduction to Java Y.Daniel Liang

PrintWriter
is an object we use to generate an output text
file.


PrintWriter

supports only two output methods:

print

println (for print line)


Run program TestPrinterWriter


output file: pw.txt




20

Introduction to Java Y.Daniel Liang


Constructors of the
PrintWriter




PrintWriter(Writer out)


PrintWriter(Writer out, boolean
autoFlush)


PrintWriter(OutputStream out)


PrintWriter(OutputStream out, boolean
autoFlush)

21

PrintWriter

Methods


Introduction to Java Y.Daniel Liang




void print(Object o)


void print(String s)


void println(String s)


void print(char c)


void print(char[] cArray)


void print(int i)


void print(long l)


void print(float f)


void print(double d)


void print(boolean b)

22

Streams

In Java, all I/O is handled in streams.


A
stream

is an abstraction of the continuous one
-
way flow of data. The program

receives data thru the input stream and sends data thru the output stream.


Any source of input or destination for output is called a stream.

Program
Output Stream
File
Input Stream
Introduction to Java Y.Daniel Liang

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Introduction to Java Y.Daniel Liang

Introduction to Java Y.Daniel Liang

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Streams


All streams except random
-
access file
streams flow in only one direction;
therefore if you want to input and output,
you need two separate stream objects.



Streams are objects. Stream objects have
methods that read and write data , flush the
stream, close the stream, and count the
number of bytes in the stream, etc.




Introduction to Java Y.Daniel Liang

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25

Binary I/O

Text I/O requires encoding and decoding. The JVM converts a
Unicode to a file specific encoding when writing a character and
coverts a file specific encoding to a Unicode when reading a
character.


Binary I/O does not require conversions. When you write a byte to
a file, the original byte is copied into the file. When you read a byte
from a file, the exact byte in the file is returned.


Text I/O program

The Unicode of
the character

Encoding/

Decoding


Binary I/O program

A byte is read/written


(b)

(a)

e.g.
,

"199"

The encoding of the character
is stored in the file


0x31

e.g.
,

199

0
0110111

0
0110001 00111001 00111001

0x39

0x39

0xC7


The same byte in the file


Introduction to Java Y.Daniel Liang

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Binary I/O Classes


The design of the Java I/O classes is a good example of
applying inheritance, where common methods are generalized
in superclasses, and sub classes provide specialized methods.


See next slide. It list some of the classes for performing
binary I/O.


InputStream is the root for binary input classes.


OutputStream is the root for binary output classes

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Introduction to Java Y.Daniel Liang

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Binary I/O Classes


InputStream

OutputStream

Object

ObjectOutputSt
ream

FilterOutputStream

FileOutputStream

BufferedInputStream

DataInputStream

BufferedOutputStream

DataOutputStream

PrintStream

ObjectInputStream

FilterInputStream

FileInputStream

Stream Classes


The stream classes can be categorized into two types:
byte
streams

and
character streams
.


The
InputStream/OutputStream

class is the

root of all byte stream classes,




the
Reader/Writer

class is the root of all character
stream.




The subclasses of
InputStream/

OutputStream

are analogous to the

subclasses of
Reader/Writer
.


Introduction to Java Y.Daniel Liang

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Introduction to Java Y.Daniel Liang

To Read and Write Binary Data from /To a Disk File


FileInputStream and FileOutputStream
-

all methods in these
classes are inherited from InputStream and OutputStream

(java.io. FileInputStream and java.io.FileOutputStream )


Create a FileInputStream:


FileInputStream inputStream = new


FileInputStream inputStream (


“input.bin”);


To write Binary Data to a Disk File:


FileOutputStream outputStream = new


FileOutputStream outputStream (


“output.bin”);




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InputStream

java.io.InputStream


int read(byte[] b) throws IOException


abstract int read() throws IOException


void close() throws IOException


int available() throws IOException


long skip(long n) throws IOException


Note: The
abstract

InputStream class defines
the methods for the input stream of bytes


Introduction to Java Y.Daniel Liang

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OutputStream

java.io.OutputStream


abstract void write(int b) throws
IOException


void write(byte[] b) throws IOException


void close() throws IOException


void flush() throws IOException



Note: The
abstract

OutputStream class
defines the methods for the output
stream of bytes.

Introduction to Java Y.Daniel Liang

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FileInputStream/FileOutputStream

FileInputStream/FileOutputStream associates a
binary input/output stream with an external file.

All the methods in
FileInputStream/FileOuptputStream are inherited
from its superclasses.


InputStream

OutputStream

Object

ObjectOutputSt
ream

FilterOutputStream

FileOutputStream

BufferedInputStream

DataInputStream

BufferedOutputStream

DataOutputStream

PrintStream

ObjectInputStream

FilterInputStream

FileInputStream

Introduction to Java Y.Daniel Liang

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FileInputStream

To construct a FileInputStream, use the following
constructors:

public FileInputStream(String filename)

public FileInputStream(File file)


A
java.io.FileNotFoundException

would occur if you attempt to
create a
FileInputStream

with a nonexistent file.

Introduction to Java Y.Daniel Liang

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FileOutputStream

To construct a FileOutputStream, use the following constructors:


public FileOutputStream(String filename)

public FileOutputStream(File file)

public FileOutputStream(String filename, boolean append)

public FileOutputStream(File file, boolean append)



If the file does not exist, a new file would be created. If the file already
exists, the first two constructors would delete the current contents in
the file. To retain the current content and append new data into the
file, use the last two constructors by passing true to the append
parameter.

Introduction to Java Y.Daniel Liang

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FileOutputStream


The program TestFileStream uses binary I/O to
write ten bytes values from 1 to 10 to a file
named temp.dat

TestFileStream

Run

Introduction to Java Y.Daniel Liang

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FilterInputStream/FilterOutputStream

Filter streams

are streams that filter bytes for some purpose. The basic byte input stream provides
a read method that can only be used for reading bytes.

If you want to read integers, doubles, or strings, you need a filter class to wrap the byte input
stream. Using a filter class enables you to read integers, doubles, and strings instead of bytes and
characters.
FilterInputStream

and
FilterOutputStream

are the base classes for filtering data.


When you need to process primitive numeric types, use
DatInputStream

and
DataOutputStream

to filter bytes.


InputStream

OutputStream

Object

ObjectOutputSt
ream

FilterOutputStream

FileOutputStream

BufferedInputStream

DataInputStream

BufferedOutputStream

DataOutputStream

PrintStream

ObjectInputStream

FilterInputStream

FileInputStream

Introduction to Java Y.Daniel Liang

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DataInputStream/DataOutputStream

DataInputStream

reads bytes from the stream
and converts them into appropriate primitive
type values or strings.


InputStream

OutputStream

Object

ObjectOutputSt
ream

FilterOutputStream

FileOutputStream

BufferedInputStream

DataInputStream

BufferedOutputStream

DataOutputStream

PrintStream

ObjectInputStream

FilterInputStream

FileInputStream

DataOutputStream

converts primitive type values
or strings into bytes and output the bytes to the
stream.

Introduction to Java Y.Daniel Liang

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DataInputStream

DataInputStream

extends
FilterInputStream

and implements the
DataInput

interface.


java.io.DataInput


+readBoolean(): boolean

+readByte(): byte

+readChar(): char

+readFloat(): float

+readDouble(): float

+readInt(): int

+readLong(): long

+readShort(): short

+readLine(): String

+readUTF(): String


Reads a
Boolean from the input stream.

Reads a byte from the input stream.

Reads a character from the input stream.

Reads a float from the input stream.

Reads a double from the input stream.

Reads an int from the input stream.

Reads a long from the input stream.

R
eads a short from the input stream.

Reads a line of characters from input.

Reads a string in UTF format.


InputStream


FilterInputStream


DataInputStream

+DataInputStream(

in: InputStream)

Introduction to Java Y.Daniel Liang

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DataOutputStream

DataOutputStream

extends
FilterOutputStream

and implements the
DataOutput

interface.


java.io.DataOutput


+writeBoolean(b: Boolean): void

+writeByte(v: int): void


+writeBytes(s: String): void

+writeChar(c: char): void

+writeChars(s: String): void

+writeFloat(v: float): void

+writeDouble(v: float): void

+wri
teInt(v: int): void

+writeLong(v: long): void

+writeShort(v: short): void

+writeUTF(s: String): void


Writes a Boolean to the output stream.

Writes to the output stream the eight low
-
order bits
of the argument v.

Writes the lower byte of the characters i
n a string to
the output stream.

Writes a character (composed of two bytes) to the
output stream.

Writes every character in the string s, to the output
stream, in order, two bytes per character.

Writes a float value to the output stream.

Writes a double
value to the output stream.

Writes an int value to the output stream.

Writes a long value to the output stream.

Writes a short value to the output stream.

Writes two bytes of length information to the output
stream, followed by the UTF representation of
ev
ery character in the string s.


OutputStream


FilterOutputStream


DataOutputStream

+
DataOutputStream(

out: OutputStream)


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Characters and Strings in Binary I/O


A Unicode consists of two bytes. The
writeChar(char c)

method writes the Unicode of
character
c

to the output.


The
writeChars(String s)

method writes the
Unicode for each character in the string
s

to the
output.

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41

Characters and Strings in Binary I/O


Why UTF
-
8? What is UTF
-
8?


UTF
-
8 (8
-
bit UCS/Unicode Transformation Format) is a coding
scheme that allows systems to operate with both ASCII and Unicode
efficiently. Most operating systems use ASCII.



Java uses Unicode. The ASCII character set is a subset of the
Unicode character set. Since most applications need only the ASCII
character set, it is a waste to represent an 8
-
bit ASCII character as a
16
-
bit Unicode character.




Introduction to Java Y.Daniel Liang

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42

Characters and Strings in Binary I/O


Why UTF
-
8? What is UTF
-
8?




The UTF
-
8 is an alternative scheme that stores a character using 1, 2,
or 3 bytes. ASCII values (less than 0x7F) are coded in one byte.

Unicode values less than 0x7FF are coded in two bytes. Other
Unicode values are coded in three bytes.

Introduction to Java Y.Daniel Liang

Using
DataInputStream
/
DataOutputStream


Data streams are used as wrappers on existing input and output
streams to filter data in the original stream. They are created using the
following constructors:


public DataInputStream(InputStream instream)

public DataOutputStream(OutputStream outstream)



The statements given below create data streams. The first statement
creates an input stream for file
in.dat
; the second statement creates an
output stream for file
out.dat
.


DataInputStream infile =


new DataInputStream(new FileInputStream("in.dat"));

DataOutputStream outfile =


new DataOutputStream(new FileOutputStream("out.dat"));

Introduction to Java Y.Daniel Liang

Using
DataInputStream
/
DataOutputStream



DataInputStream and DataOutputStream
read and write data primitive
types values and strings in a machine
-
independent fashion.


Thereby enabling you to write a data file on one machine and read it
on another machine that has a different operating system or file
structure.


An application uses a data output stream to write data that can later be
read by a program using a data input stream.

Introduction to Java Y.Daniel Liang

Using
DataInputStream
/
DataOutputStream


The TestDataStream program writes student names and
scores to a file named temp.dat and reads the data back from
the file.

TestDataStream

Run

Introduction to Java Y.Daniel Liang

46

Checking End of File

TIP: If you keep reading data at the end of a stream, an
EOFException

would occur. So how do you check the end of a file? You can use
input.available()

to check it.
input.available() == 0

indicates that it is
the end of a file.

Order and Format

See program TestDataStream


CAUTION: You have to read the data in the same order and same
format in which they are stored. For example, since names are written
in UTF
-
8 using
writeUTF
, you must read names using
readUTF
.


Introduction to Java Y.Daniel Liang

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47

BufferedInputStream/BufferedOutputStream

Reduces the number of reads and writes

Using buffers to speed up I/O


InputStream

OutputStream

Object

ObjectOutputSt
ream

FilterOutputStream

FileOutputStream

BufferedInputStream

DataInputStream

BufferedOutputStream

DataOutputStream

PrintStream

ObjectInputStream

FilterInputStream

FileInputStream

BufferedInputStream
/
BufferedOutputStream

does not contain new
methods.

All the methods
BufferedInputStream
/
BufferedOutputStream

are inherited
from the
InputStream
/
OutputStream

classes.


Introduction to Java Y.Daniel Liang

48

Constructing
BufferedInputStream
/
BufferedOutputStream


// Create a BufferedInputStream

public BufferedInputStream(InputStream in)

public BufferedInputStream(InputStream in, int bufferSize)




// Create a BufferedOutputStream

public BufferedOutputStream(OutputStream out)

public BufferedOutputStream(
OutputStream

out, int bufferSize)

Introduction to Java Y.Daniel Liang

49

Constructing
BufferedInputStream
/
BufferedOutputStream


Improve the performance of the TestDataStream program by
adding buffers in the streams in lines 6
-
7 and 21
-
22, as follows:


DataOutputStream output =
new

DataOutputStream(


new BufferedOutputStream(new


FileOutputStream(“temp.dat”));


DataInputStream input =
new

DataInputStream(


new BufferedInputStream(new


FileInputStream(“temp.dat”));







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50

Case Studies: Copy File

This case study develops a program that copies files. The user needs
to provide a source file and a target file as command
-
line arguments
using the following command:



java Copy source target





The program copies a source file to a target file and displays the
number of bytes in the file. If the source does not exist, tell the user
the file is not found. If the target file already exists, tell the user the
file already exists.

Introduction to Java Y.Daniel Liang

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51

Case Studies: Copy File

The program uses the File class to check whether the source file
and the target file exist.


The program copies a Java source file to an identical Java file





Copy

Run

Introduction to Java Y.Daniel Liang

52

Object I/O

DataInputStream
/
DataOutputStream

enables you to perform I/O for
objects in addition to primitive type values and strings.
ObjectInputStream
/
ObjectOutputStream

enables you to perform I/O
for objects in addition for primitive type values and strings.


InputStream

OutputStream

Object

ObjectOutputSt
ream

FilterOutputStream

FileOutputStream

BufferedInputStream

DataInputStream

BufferedOutputStream

DataOutputStream

PrintStream

ObjectInputStream

FilterInputStream

FileInputStream

Optional

Introduction to Java Y.Daniel Liang

53

ObjectInputStream

ObjectInputStream

extends
InputStream

and
implements
ObjectInput

and
ObjectStreamConstants
.



java.io.ObjectInput

+readObject(): Object



Reads an object.


java.io.InputStream


java.io.ObjectInputStream

+ObjectInputStream(in: InputStream)

java.io.DataInput


ObjectStreamConstants

Introduction to Java Y.Daniel Liang

54

ObjectOutputStream

ObjectOutputStream extends OutputStream and
implements
ObjectOutput

and
ObjectStreamConstants
.


java.io.ObjectOutput

+writeObject(o: Object): void



Writes an object.


java.io.OutputStream


java.io.ObjectOutputStream

+ObjectOutputStream(out: OutputStream)

java.io.DataOutput


ObjectStreamConstants

Introduction to Java Y.Daniel Liang

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Using Object Streams

You may wrap an
ObjectInputStream
/ObjectOutputStream on any
InputStream
/
OutputStream

using the following constructors:


// Create an ObjectInputStream

public
ObjectInputStream
(
InputStream

in)



// Create an ObjectOutputStream

public ObjectOutputStream(
OutputStream

out)

TestObjectOutputStream

Run

TestObjectInputStream

Run

Introduction to Java Y.Daniel Liang

56

Object Streams

The ObjectInputStream class can save entire object out to a
disk, and the C class can read them back in.


Objects are saved in binary format; therefore, you use streams
and not writers.

For example, you can write a Bank Account object to a file:


BankAccount bk = new …;


ObjectOutputStream out = new ObjectOutputStream (


new FileOutputStream(“bank.dat”));

Out.writeObject(bk);






Introduction to Java Y.Daniel Liang

57

Object Streams

Use Object streams to save and restore all instance fields of an
object automatically.


When reading the object back in, you use the r
eadObject
method of the
ObjectInputStream

class. That method returns
an Object reference, so you need to remember the types of the
objects that you saved and use a cast:



ObjectInputStream in = new ObjectInputStream (


new FileInputStream(“bank.dat”));

BankAccount bk = (BankAccount) in.read
Object(

);


The readObject method can throw a ClassNotFoundException
-
it is a checked exception, so you need to catch or declare it.






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The
Serializable

Interface

Not all objects can be written to an output stream. Objects that can be
written to an object stream is said to be
serializable
. A serializable
object is an instance of the
java.io.Serializable

interface. So the class
of a serializable object
must implement

Serializable
.


The
Serializable

interface is a marker interface. It has no methods, so
you don't need to add additional code in your class that implements
Serializable
.


public MyClass implements
Serializable{

// Definition of the class

}

Implementing this interface enables the Java serialization mechanism
to automate the process of storing the objects and arrays.

Introduction to Java Y.Daniel Liang

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The
transient

Keyword

If an object is an instance of
Serializable
, but it contains
non
-
serializable instance data fields, can the object be
serialized?


The answer is no.


To enable the object to be serialized, you can use the
transient

keyword to mark these data fields to tell the JVM
to ignore these fields when writing the object to an object
stream.

Introduction to Java Y.Daniel Liang

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The
transient

Keyword, cont.

Consider the following class:



public class Foo implements java.io.Serializable {


private int v1;


private
static

double v2;


private
transient

A v3 = new A();

}

class A { } // A is not
serializable



When an object of the Foo class is serialized, only variable v1 is
serialized.

Variable v2 is not serialized because it is a static variable, and

variable v3 is not serialized because it is marked transient. If v3 were
not marked transient, a java.io.NotSerializableException would occur.

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Serializing Arrays


An array is
serializable

if all its elements are
serializable
.
So an entire array can be saved using
writeObject

into a file
and later restored using
readObject
. Listing 16.12 stores an
array of five
int

values an array of three strings, and an
array of two
JButton

objects, and reads them back to
display on the console. Note :
java.io.File

implements
Comparable and Serializable

TestObjectStreamForArray

Run

Introduction to Java Y.Daniel Liang

62

More about the Serializable Interface

The process of saving objects to a stream is called serialization because
each object is assigned a serial number on the stream. If the same object
is saved twice, only the serial number is written out the second time.


When the objects are read back in, duplicate serial numbers are restored
as reference to the same object.


Why don’t all classes implement
Serializable
?

For security reasons, some programmers may not want to serialize
classes with confidential contents. Once a class is serializable, anyone
can write its objects to disk and analyze the disk file.


There are also some classes that contain values that are meaningless once
a program exists, such as operating

system
-
specific font descriptors.

These values should not be serialized.







Introduction to Java Y.Daniel Liang

63

Random Access Files

All of the streams you have used so far are known as
read
-
only

or
write
-
only

streams.


The external files of these streams are
sequential

files that
cannot be updated without creating a new file.



It is often necessary to modify files or to insert new
records into files.


Java provides the
RandomAccessFile

class to allow a file
to be read from and
writen

to at random locations.

Introduction to Java Y.Daniel Liang

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RandomAccessFile


Creates a RandomAccessFile stream with the specified File object and
mode.

Creates a RandomAccessFile stream with the specified file name
string and mode.

Closes the stream and releases the resource associated with the stream.

Ret
urns the offset, in bytes, from the beginning of the file to where the
next read or write occurs.

Returns the length of this file.

Reads a byte of data from this file and returns

1 an the end of stream.

Reads up to b.length bytes of data from this file in
to an array of bytes.

Reads up to len bytes of data from this file into an array of bytes.

Sets the offset (in bytes specified in pos) from the beginning of the
stream to where the next read or write occurs.

Sets a new length of this file.

Skips over n byt
es of input discarding the skipped bytes.

Writes b.length bytes from the specified byte array to this file, starting
at the current file pointer.

Writes len bytes from the specified byte array starting at offset off to
this file.

DataInput


DataInput


java.io.Ran
domAccessFile


+RandomAccessFile(file: File, mode:
String)

+RandomAccessFile(name: String,
mode: String)

+close(): void

+getFilePointer(): long

+length(): long

+read(): int

+read(b: byte[]): int

+read(b: byte[], off: int, len: int) : int

+seek(long pos)
: void

+setLength(newLength: long): void

+skipBytes(int n): int

+write(b: byte[]): void

+write(byte b[], int off, int len)

+write(b: byte[], off: int, len: int):
void