Download FileOutputStream(File fileObject) throws IOException

JAVA Programming Language
Chapter 9. Input/Output with Java.io
Juho Kim
Department of Computer Science and Engineering
Sogang University
9 -1
java.io package
Provides for system input and output through data streams, serialization
and the file system. Java Virtual Machine connects data stream to
input/output hardware. Data stream makes JAVA I/O independent of
machines
File and Directory
FileWriter FileReader class
BufferedWriter BufferedReader class
FileOutputStream FileInputStream class
BufferedOutputStream BufferedInputStream class
DataOutputStream DataInputStream class
9-2
File class
File and Directory
– File class: An abstract representation of file and directory pathnames.
User interfaces and operating systems use system-dependent pathname
strings to name files and directories. This class presents an abstract,
system-independent view of hierarchical pathnames
• Constructor
File(File parent, String child)
Creates a new File instance from a parent abstract pathname and a
child pathname string.
File(String pathname)
Creates a new File instance by converting the given pathname string
into an abstract pathname
File(String pathname, String filename)
Creates a new File instance by pathname string and filename string
9 -3
• Methods
boolean canRead()
if readable return true
boolean canWrite()
if write allowed return true
boolean delete()
delete file and return true
boolean exists()
String getAbsolutePath() return pathname
String getParent()
return parent directory name
String getName()
return file name
boolean isFile()
boolean isDirectory()
long lastModified()
return milliseconds from 1970/1/1 until last
modified time
String[] list()
return filenames from directory
9 -4
FileDirDemo1.java
import java.io.File;
class FileDirDemo1 {
public static void main(String args[]) {
String directory = "c:/jdk1.4";
File f1 = new File(directory);
if (f1.isDirectory()) {
System.out.println("Directory : " + directory);
System.out.println(" ");
String s[] = f1.list();
for(int i=0; i<s.length; i++) {
File f = new File(directory + "/" + s[i]);
if (f.isDirectory()) {
System.out.println(s[i] + " : directory");
} else {
System.out.println(s[i] + " : file"); }}}
else {
System.out.println(“this" +directory + " is not a directory");
}
}}
9 -5
FileDirDemo2.java
import java.io.File;
class FileDirDemo2
{
static void p(String s)
{
System.out.println(s);
}
public static void main(String args[])
{
File f1 = new File("c:/jdk1.4/README.txt");
p("f1.getName(): " + f1.getName());
p("f1.getPath(): " + f1.getPath());
p("f1.getAbsolutePath(): " + f1.getAbsolutePath());
p("f1.exists(): " + f1.exists());
p("f1.canWrite(): " + f1.canWrite());
p("f1.canRead(): " + f1.canRead());
p("f1.isDirectory(): " + f1.isDirectory());
p("f1.isFile(): " + f1.isFile());
p("f1.lastModified(): " + f1.lastModified());
p("f1.length(): " + f1.length() + " bytes");
}}
9 -6
FireWriter and FileReader class
– Constructor
FileWriter(String filepath) throws IOException
FileWriter(String filepath, boolean append) throws IOException
FileWriter(File fileObject) throws IOException
FileReader(String filepath)
FileReader(File fileObject)
9 -7
– Methods
void close()
closing input/output stream
void flush()
sending data in output buffer to output
device
void write(int c)output lower 16-bit of c
void write(char buffer[]) output from buffer array
void write(char buffer[], int index, int size)
void write(String s)
void write(String s, int index, int size)
int read()
return character, if end of file return -1
int read(char buffer[])
int read(char buffer[], int offset, int numChars)
9 -8
FileWriterDemo.java
import java.io.*;
class FileWriterDemo
{
public static void main(String args[]) throws Exception
{
String source = "File Writer \nDemonstration";
char intxt[] = new char[source.length()];
source.getChars(0, source.length(), intxt, 0);
FileWriter fw = new FileWriter(args[0]);
fw.write(intxt);
fw.close();
}
}
9 -9
FileReaderDemo.java
import java.io.*;
class FileReaderDemo
{
public static void main(String args[]) throws Exception
{
FileReader fr = new FileReader(args[0]);
int i;
while((i = fr.read()) != -1)
{
System.out.print((char) i);
}
fr.close();
}
}
9 -10
BufferedWriter and BufferedReader class
– BufferedWriter class
Write text to a character-output stream, buffering characters so as to
provide for the efficient writing of single characters, arrays, and strings.
The buffer size may be specified, or the default size may be accepted.
The default is large enough for most purposes.
– BufferedReader class
Read text from a character-input stream, buffering characters so as to
provide for the efficient reading of characters, arrays, and lines.
The buffer size may be specified, or the default size may be used. The
default is large enough for most purposes.
9 -11
– Constructor
BufferedWriter(Writer outputStream)
BufferedWriter(Writer outputStream, int bufSize)
BufferedReader(Reader inputStream)
BufferedReader(Reader inputStream, int bufSize)
Writer class : Abstract class for writing to character streams
Reader class : Abstract class for reading to character streams
9 -12
BufferedWriterDemo.java
import java.io.*;
class BufferedWriterDemo
{
public static void main(String args[]) throws Exception
{
String source = "Buffered Writer \nDemonstration";
char intxt[] = new char[source.length()];
source.getChars(0, source.length(), intxt, 0);
FileWriter fw = new FileWriter(args[0]);
BufferedWriter bw = new BufferedWriter(fw);
bw.write(intxt);
bw.close();
}
}
9 -13
BufferedReaderDemo.java
import java.io.*;
class BufferedReaderDemo
{
public static void main(String args[]) throws Exception
{
FileReader fr = new FileReader(args[0]);
BufferedReader br = new BufferedReader(fr);
String s;
while((s = br.readLine()) != null)
{
System.out.print(s);
}
br.close();
}
}
9 -14
FileOutputStream and FileInputStream
– OutputStream class
• This abstract class is the superclass of all classes representing an
output stream of bytes. An output stream accepts output bytes and
sends them to some sink.
• Applications that need to define a subclass of OutputStream must
always provide at least a method that writes one byte of output.
– InputStream class
• This abstract class is the superclass of all classes representing an
input stream of bytes.
• Applications that need to define a subclass of InputStream must
always provide a method that returns the next byte of input.
9 -15
– FileOutputStream
java.lang.Object
|
+ --java.io.OutputStream
|
+ --java.io.FileOutputStream
public class FileOutputStream
extends OutputStream
A file output stream is an output stream for writing data to a File or to a
FileDescriptor. What files are available or may be created depends on the
host environment.
9 -16
– Constructor
FileOutputStream(String filepath) throws IOException
filepath constains pathname and filename
FileOutputStream(String filepath, boolean append) throws IOException
if append is true, append at the end of the file
otherwise, overwirte
FileOutputStream(File fileObject) throws IOException
fileObject is a specific file
9 -17
– FileInputStream class
java.lang.Object
|
+ --java.io.InputStream
|
+ --java.io.FileInputStream
public class FileInputStream
extends InputStream
A FileInputStream obtains input bytes from a file in a file system. What files are
available depends on the host environment.
–
Constructor
FileInputStream(String filepath) throws FileNotFoundException
FileInputStream(File fileObject) throws FileNotFoundException
9 -18
FileOutputStreamDemo.java
import java.io.*;
class FileOutputStreamDemo
{
public static void main(String args[]) throws IOException
{
FileOutputStream fos = new FileOutputStream(args[0]);
for(int i = 0; i < 5; i++)
{ fos.write(i);
}
fos.close();
System.out.println("ByteStreamFile is created");
}
}
9 -19
FileInputStreamDemo.java
import java.io.*;
class FileInputStreamDemo
{
public static void main(String args[]) throws IOException
{
FileInputStream fis = new FileInputStream(args[0]);
int i;
while((i = fis.read()) != -1)
{
System.out.println(i);
}
fis.close();
System.out.println("ByteStreamFile is read and printed");
}
}
9 -20
BufferedOutputStream and BufferedInputStream class
– The class BufferedOutputStream implements a buffered output stream.
By setting up such an output stream, an application can write bytes to
the underlying output stream without necessarily causing a call to the
underlying system for each byte written. The data is written into an
internal buffer, and then written to the underlying stream if the buffer
reaches its capacity, the buffer output stream is closed, or the buffer
output stream is explicitly flushed.
– When the BufferedInputStream is created, an internal buffer array is
created. As bytes from the stream are read or skipped, the internal
buffer is refilled as necessary from the contained input stream, many
bytes at a time.
9 -21
BufferedOutputStreamDemo.java
import java.io.*;
class BufferedOutputStreamDemo
{ public static void main(String args[]) throws IOException
{ FileOutputStream fos = new FileOutputStream(args[0]);
BufferedOutputStream bos = new BufferedOutputStream(fos);
for(int i = 0; i < 5; i++)
{ bos.write(i);
}
bos.close();
System.out.println("ByteStreamFile is created");
}
}
9 -22
BufferedInputStreamDemo.java
import java.io.*;
class BufferedInputStreamDemo
{ public static void main(String args[]) throws IOException
{ FileInputStream fis = new FileInputStream(args[0]);
BufferedInputStream bis = new BufferedInputStream(fis);
int i;
while((i = bis.read()) != -1)
{ System.out.println(i);
}
bis.close();
System.out.println("ByteStreamFile is read and printed");
}
}
9 -23
DataOutputStream and DataInputStream class
– A data output stream lets an application write primitive Java data types
to an output stream in a portable way. An application can then use a
data input stream to read the data back in.
– A data input stream lets an application read primitive Java data types
from an underlying input stream in a machine-independent way. An
application uses a data output stream to write data that can later be
read by a data input stream.
– Constructor
DataOutputStream(OutputStream outputStream)
DataInputStream(InputStream inputStream)
9 -24
9 -25
9 -26
DataOutputStreamDemo.java
import java.io.*;
class DataOutputStreamDemo
{ public static void main(String args[])throws IOException
{ FileOutputStream fos = new FileOutputStream(args[0]);
DataOutputStream dos = new DataOutputStream(fos);
dos.writeBoolean(false);
dos.writeByte(Byte.MAX_VALUE);
dos.writeChar('A');
dos.writeDouble(Double.MAX_VALUE);
dos.writeFloat(Float.MAX_VALUE);
dos.writeInt(Integer.MAX_VALUE);
dos.writeLong(Long.MAX_VALUE);
dos.writeShort(Short.MAX_VALUE);
fos.close();
}
}
9 -27
DataInputStreamDemo.java
import java.io.*;
class DataInputStreamDemo
{ public static void main(String args[])throws IOException
{ FileInputStream fis = new FileInputStream(args[0]);
DataInputStream dis = new DataInputStream(fis);
System.out.println("Boolean : " + dis.readBoolean());
System.out.println("Byte.MAX_VALUE : " + dis.readByte());
System.out.println("Character : " + dis.readChar());
System.out.println("Double.MAX_VALUE : " + dis.readDouble());
System.out.println("Float.MAX_VALUE : " + dis.readFloat());
System.out.println("Integer.MAX_VALUE : " + dis.readInt());
System.out.println("Long.MAX_VALUE : " + dis.readLong());
System.out.println("Short.MAX_VALUE : " + dis.readShort());
fis.close();
}
}
9 -28