1. Input & Output in Java Lecture12 Application Program JOHN DOE'S DISK
MYFILE.DAT

2. Use the standard streams System.in， System.out System.err
Objectives
Perform stream input/output with the core classes in the package java.io
Use the standard streams System.in， System.out System.err
Distinguish between byte-oriented and character-oriented streams
Write code that uses objects of the file class to navigate a file system
Select valid constructor for FilterInputStream and FilterOutputStream subclasses from a list of classes in the java.io package
Write appropriate code to read,write,and update files using FileInputStream,FileOutputStream,and RandomAccessFile objects

3. Based on Stream input and output
java.io
Standard Java package
Define classes for Input/Output
Very general
-Support console,files,netwoek connections,…
Support raw IO, formatted IO,…
The package does not provide facilities for drawing or displaying graphical components on the screen
Also it does not support the mouse
Based on Stream input and output
i.e., raw input/output consists of a stream of bytes
We just treat each byte as a binary value

4. Streams
A stream is an abstraction of the continuous one-way flow of data.
no inherent records or lines; no direct access to any locations

5. Input Streams vs.Output Stream
Java uses streams to facilitate input and output operations
Input streams are used to “read” data
Output streams are used to “write” data

6. Java I/O

7. Communications Channel
Java I/O Streams(1)
Streams can also be viewed as the endpoints of a one-way communications channel, which connects an output stream to a corresponding input stream
write
read
Communications Channel
Output Stream
Input Stream
Everything that is written to the output stream can be read from the input stream

8. Streams can, therefore, provide a uniform interface
Java I/O Streams(2)
The communications channel can be a network link, a memory buffer, a file, or a terminal to the user
No matter where the information is coming from or going to and no matter what type of data is being read or written, the algorithms for reading and writing data are pretty much the same
Streams can, therefore, provide a uniform interface

9. Streams are FIFO (first-in first-out)
Java I/O Streams(3)
Streams are FIFO (first-in first-out)
e.g., if a sequence of numbers is written to an output stream, they will be written to their destination in the same order and read from a corresponding input stream in the same order
exception: RandomAccessFile
Blocking I/O
reads and writes must wait for the I/O operation to complete before returning

10. Characters Streams vs. Bytes Streams
The java.io package contains a collection of stream classes
These classes are divided into two class hierarchies based on the data type (either characters or bytes) on which they operate

11. Bytes Stream
InputStream and OutputStream are the abstract superclasses for byte streams in Java
InputStream provides the API and partial implementation for input streams
--streams that read 8-bit bytes
OutputStream provides the API and partial implementation for output streams
--streams that write 8-bit bytes
These streams are typically used to read and write binary data such as images and sounds

12. Byte-Oreiented Stream Classes

13. Subclasses of InputStream and OutputStream
Object
File
OutputStream
RandomAcessFile
InputStram
StreamTokenizer
FileDescriptor
ByteArrayOutputStream
PipedOutputStream
FileOutputStream
FilterOutputStream
PrintStream
BufferedOutputStream
DataOutputStream
SequenceInputStream
StringBufferInputStream
ByteArrayInputStream
PipedInputStream
FileInputStream
FilterInputStream
LineNumberInputStream
BufferedInputStream
DataInputStream
PushbackInputStream
DataInput
DataOutput

14. Predefined Stream Objects
All java programs can use three stream objects that are defined in the System class
System.in
is a java.io.BufferedInputStream object
this object encapsulates keyboard input
System.out
is a java.io.PrintStream object
this object encapsulates output to a command-line window and is used for most command-line mode output
can redirect the output to a file
System.err
Output sent to System.err goes to a command line and can be mixed with output to System.out

15. Input and Output Methods
InputStream:
abstract int read() throws IOException
int read(byte b[]) throws IOException
void close() throws IOException
void available() throws IOException
long skip(long n) throws IOException
OutputStream:
abstract void write(int b) throws IOException
void write(byte[] b) throws IOException
void close() throws IOException
void flush() throws IOException

16. InputStream Example
import java.io.*; //计算文件中的字符数和空白字符数
class CountSpace{
public static void main(String[] args) throws IOException
{ InputStream in;
if (args.length==0) in=system.in;
else in=new FileInputStream(args[0]);
int ch; int total; int spaces=0;
for(total=0;(ch=in.read())!=-1;total++){
if (Charater.isSpace((char)ch) spaces++; }
System.out.println(total+”chars,”+spaces+”spaces”);

17. OutputStream Example（1）
import java.io.*;//将输入的数据拷贝输出，并转化特定字符
class Translate{
public static void main(String[] args){
InputStream in=System.in;
OutputStream out=System.out;
if (args.length!=2)
error(“from/to needed”);
String from=args[0], to=args[1];
int ch，i;
if (from.length()!=to.length())
error(“same length needed”);

18. OutputStream Example（2）
try{ while((ch=in.read())!=-1){
if ((i=from.indexOf(ch))!=-1)
out.write(to.charAt(i));
else out.write(ch); }
}catch(IOException e) { error(“I/O Exception:”+e); }
public static void error(String err){
System.err.print(“Translate:”+err);
System.exit(1); //非零值意指“不好”

19. when you want to do more than read and write bytes and chars ...
Filtered Streams
when you want to do more than read and write bytes and chars ...
Stream filters provide enhanced functionality on top of other existing streams
The basic approach is to layer stream filters on top of more primitive streams
Filter streams add new constructors to the basic ones in the InputStream and OutputStream classes, and enable you to chain streams to produce composite streams of greater power

20. Byte-oriented Filter Streams
FilterInputStream, FilterOutputStream:
DataInputStream, DataOutputStream
These classes transmit data of specific types across a stream instead of treating a stream as a sequence of independent bytes.You can also call methods of these classes to read and write the binary representations of the primitives types
BufferedInputStream, BufferedOutputStream
These classes provide buffering for input and output operations
PrintStream
This class implements methods for displaying data types textually(print,println)
PushbackInputStream
This class maintains a one-byte push-back buffer
LineNumberInputStream
provides an object to keep track of line numbers while reading input

21. Data Streams and Interfaces
While reading and writing bytes is useful, there is also a frequent need to transmit data of specific types across a stream
The DataInput and DataOutput interfaces defines methods to transmit Java primitive types across a stream
A default implementation of each interface is provided by the classes DataInputStream and DataOutputStream

22. Basic input/output method
Read Write Type
readBoolean writeBoolean boolean
readChar writeChar char
readByte writeByte byte
readShort writeShort short
readInt writeInt int
readLong writeLong long
readFloat writeFloat float
readDouble writeDouble double
readUFT writeUFT String(UTF format)

23. Other DataInput methods
public abstract void readFully(byte[] buf) throws IOException
public abstract void readFully(byte[] buf,int off,int len) throws IOException
public abstract int skipBytes(int n) throws IOException
public abstract String readLine() throws IOException
public abstract int readUnsignedByte() throws IOException
public abstract int readUnsignedShort(byte[] buf) throws IOException
The DataInput interface handles end-of –file by throwing an EOFException when it occurs. EOFException is an extended class of IOException

24. Other DataOutput methods
The DataOutput interface supports signatures equivalent to the three forms of write in OutputStream
public abstract void writeBytes(String s) throws IOException
public abstract void writeChars(String s) throws IOException
DataInputStream/DataOutputStream:
For each Data interface, there is a corresponding Data stream
Each Data class is an extension of its Filter class, so Data streams can be used to filter other streams
Constructor parameters: InputStream in/OutputStream out

25. Example
int account ;
String name;
double balance;
try { input=new DataInputStream(
new FileInputStream(“client.dat”))
} catch (IOException e) {
System.err.println(“Fail to open the file”+e.toString());
System.exit(1); }
try { account = input.readInt();
name = input.readUTF();
balance = input.readDouble();
} catch (EOFException eof) { …}
catch (IOException e) {…}

26. Buffered Streams
The BufferedInputStream/BufferedOutputStream classes support objects that buffer their data to avoid every read or write going directly to the next stream
When a buffered stream is created, its buffer size can be specified explicitly(InputStream in, int size)，or it can use a default size[32b] (InputStream in)
BufferedOutputStream behaves similar to OutputStream
Example
OutputStream bufferedFile(String path) //为文件提供缓冲流
throws IOException
{ OutputStream out=new FileOutputStream(path);
return new BufferedOutputStream(out); }

27. PrintStream
PrintStream is used every time a print or println method invocation appears in a program
It provides print and println methods for the following types:char,int, float,object,boolean, char[],long, double, String
Two Constructors: (OutputStream out) 、
(OutputStream out, boolean autoflush)
If the autoflush boolean is true,writing a new line character ‘\n’ invokes flush
The print(String) and print(char[]) methods are synchronized. All the other print and println methods are written in terms of these two methods,so printing on a PrintStream object is thread-safe

28. A PushbackInputStream provides single-character pushback
The pushback buffer is a protected int field named pushBack. A subclass could provoide a different way to modify this character. A value of –1 means the pushback buffer is empty. Any other value means that the PushBack.read method returns pushBack as the first byte of input
Constractor parameter: (InputStream in)
unread(int ch)return the int which represent a char into input stream
Example:
This example PushbackInputStream to find the longest sequence of any single byte in its input

29. Example(1)
import java.io.*;
class SequenceCount{
public static void main(String[] args){
try{PushbackInputstream in=new …(System.in);
int max=0; //所找到的长序列
int maxB=-1; //构成该序列的字节
int b; //当前输入字节
do{
int cnt;
int bl=in.read(); //序列中的第一个字节
for(cnt=1;(b=in.read())==b1;cnt++)
continue;

30. Example(2)
if (cnt>max){
max=cnt; //记下长度
maxB=b1; //记下字节的值 }
in.unread(b); //回送下个序列的开始字节
}while(b!=-1); //读到输入的结束
System.out.println(max+”bytes of”+maxB);
}catch(IOException e){
System.out.println(e);
System.exit(1);
} //当到达一个序列结尾时，下个序列的第一个字
} // 节实际已经被读入。用unread将该字节回送

31. LineNumberInputStream
The LineNumberInputStream class provides an object to keep track of line numbers while reading input
The getLineNumber method returns the current line number. Line numbering starts at 1
The current line number can be set with setLineNumber. This is useful when multiple input streams are treated as one input stream,but line numbers are needed relative to each stream
Example:This program prints the line number where the first instance of a particular character is found in a file
To ensure that the current line number from Sysytem.in:
LineNumberInputStream
lnum = new LineNumberInputStream(System.in);
System.in = lnum;

32. Example(1)
import java.io.*;
class Findchar{
public static void main(String[] args)
throws Exception {
if (args.length!=2)
throws new Exception(“need char/ file”);
int match=args[0].charAt(0);
FileInputStream
fileIn=new FileInputStream(args[1]);
LineNumberInputStream
in=new LineNumberInputStream(fileIn);

33. while((ch=in.read())!=-1){ if (ch==match){ System.out.println
Example(2)
int ch;
while((ch=in.read())!=-1){
if (ch==match){
System.out.println
(“‘“+(char)ch+”’at line”+in.getLineNumber());
System.exit(0); }
System.out.println(ch+”not found”);
System.exit(1); 返回

34. Other Byte I/O Streams(1)
The java.io package defines many classes.Extensions of InputStream include the following:
ByteArrayInputStream:lets you read an array of bytes as though it is an InpputStream object
SequenceInputStream:provides a mechanism for concatenating the data from two or more InputStream objects into a single,seamless stream
PipedInputStream:implements half a pipe and is especially useful for communication between threads
StringBufferInputStream: reads from a String instead of a byte array(the same as ByteArrayInputSteam )

35. Other Byte I/O Streams(2)
Extensions of OutputStream include the following:
ByteArrayOutputStream:sends its output into an object of type byte[]
PipedOutputStream:is the complementary class to PipedInputStream. Together, these two classes comprise a pipe that you can use for communication between threads

36. ByteArray Streams
ByteArray Streams uses a byte array as its input/output source
ByteArrayInputStream
public ByteArrayInputStream(byte[] buf)
public ByteArrayInputStream(byte[] buf,int offset,int len)
reset(): 指针移到流的开始
(2) ByteArrayOutputStream
public ByteArrayOutputStream() （32 bytes）
public ByteArrayOutputStream(int size)
public synchronized byte[] toByteArray()
public int size()
public String toString(int hiByte)

37. Example
String tmp = “abcdefghijklmnopqrstuvwxyz”;
byte b[] = new byte [tmp.length())];
tmp.getBytes(0,tmp.length(),b,0);
ByteArrayInputStream n1=new ByteArrayInputStream(b);
… n2=new ByteArrayInputStream(b,0,3); // abc
for (int i=0; i<2; i++) { // 打印大小写字母表
while ((c=n1.read())!=-1)
if (i==0) System.out.print((char)c);
else System.out.print(Character.toUpperCase(c));
System.out.println();
input.reset(); }//将读指针移到字节数组的开始

38. SequenceInputStream
The SequenceInputStream class creates a single input stream from reading one or more input streams,reading the first until last
Two constructors:one for the common case of two input streams;the other for any arbitrary number of input streams using the Enumeration abstraction

39. Example(1)
import java.io.*;
import java.util.Vector;
class Sum{
public static void main(String[] args){
InputStream in;
if (args.length==0){
in=System.in;
}else{
InputStream stringIn;
Vector inputs=new Vector(args.length);
for(int i=0;i<args.length;i++){
String arg=args[i]+“ ”;
stringIn = new StringBufferInputStream(arg);
inputs.addElement(stringIn); }

40. Example(2)
in=new SequenceInputStream(inputs.elements()); }
try{
double total=sumStream(in);
System.out.println(“The sum is”+total);
}catch(IOException e){
System.out.println(e);
System.exit(-1);
//...

41. Piped Streams
Bytes written on the input stream of a pair are those read on the output
Piped streams are thread-safe: one for reading and one for writing
Writing on one end of the pipe blocks the thread when the pipe files up
If the writer and reader are the same thread, that thread blocks permanently
Example:
This example creates a new thread to read from the output of some data generator object that writes its output onto an OutputStream object

42. Example
class Pipe{
public static void main(String[] args){
try{
PipedOutputStream out=new PipedOutputStream();
PipedInputStream in=new PipedInputStream(out);
// 数据产生器将结果写入给定的输出流中
DataGenerator data=new DataGenerator(out);
data.setPriority(Thread.MIN_PRIORITY);
data.start(); int ch;
while((ch=in.read())!=-1)
System.out.print((char)ch);
System.out.println();
}catch(IOException e){
System.out.println(“Exception:”+e); } } }

43. StringBufferInputStream
It provides a single constructor that is the string from which to read.Each character in the string is treated as a byte
Note that StringBufferInputStream operats on String object, not StringBuffer objects
There is no StringBufferOutputStream. A similar effect can be obtain by using the toString method on ByteArrayInputSteam

44. Example
class Factor {
public static void main(String[] args) {
if (args.length = = 0) {
factorNumbers(System.in); }
else {
InputStream in;
for (int i = 0; i < args.length; i ++) {
in = new StringBufferInputStream(args[i]);
factorNumbers(in);
} //…

45. Difference exits between files and the standard console I/O objects:
File I/O Basics
Programming stream I/O to and from files is much like that to and from the console
Difference exits between files and the standard console I/O objects:
Before you can use a file,you must associate the file with a FileInputStream or FileOutputStream object
If you want to access the data in a file in random-access order, you must open it as a RandomAccessFile
In a network environment, the default security restrictions do not let applets do any file I/O on the client workstation

46. (1) FileInputStream File Streams Constructor
— A constructor that takes a String that is the name of the file
— A constructor that takes a File that refers to the file
— A constructor that takes a FileDescriptor object
Methods: overwrite six methods of InputStream
InputStream f0 = new FileInputStream(“a.bat”);
File f = new File(“a.bat”);
InputStream f1 = new FileInputStream(f);
(2) FileOutputStream
Open read-only file,signals an exception
Open a file which created already,its content will be lost

47. File InputStreams Example(1)
import java.io.*; import java.util.*
class FileInputDemo {
public static void main(String args[]) throws Exception{
int size;
InputStream f1=new FileInputStream(“file.htm”);
size=f1.available(); // total size
// Read the first 1/4 by read()
for (int i=0; i<size/4; i++)
System.out.print((char)f1.read());
System.out.println(“Still available: ”+f1.available());

48. File InputStreams Example(2)
// Read the next 1/8 by read(b[])
byte b[] = new byte[size/8];
if (f1.read(b)!=b.length)
System.err.println(“Something bad happened!”);
System.out.println(“Still available: ”+f1.available());
// Skip another 1/4: skip()
f1.skip(size/4);
f1.close(); }

49. File OutputStreams Example(1)
import java.io.*
class FileOutputDemo {
public static byte getInput()[] throws Exception {
byte buffer[] = new byte[12];
for (int i=0;i<12;i++)
buffer[i]=(byte) System.in.read();
return buffer; }

50. File OutputStreams Example(2)
public static void main(String args[]) throws Exception {
byte buf[]=getInput();
OutputStream f0=new FileOutputStream(“file1.txt”);
OutputStream f1=new FileOutputStream(“file2.txt”);
OutputStream f2=new FileOutputStream(“file3.txt”);
for (int i=0;i<12;i+=2) f0.write(buf[i]);
f0.close();
f1.write(buf);
f1.close();
f2.write(buf,12/4, 12/2);
f2.close(); } }

51. The File Class(1)
The File class provides several common manipulations that are useful with filenames. It provides methods to separate pathnames into subcomponents, and for querying the file system about the file a pathname refers to
Constructors:
public File(String path) :Creates a File object to manipulate the specified path.This method throws a NullPointerException if the path parameter is null
public File(String dirName,String name)
File(dirName + File.separator +name)
public File(File fileDir,String name)
File(fileDir.getPath(), name)
Example: File f1=new File(“/”);
File f2=new File(“/”,”autoexec.bat”);
File f3=new File(f1,”autoexec.bat”);

52. The File Class(2)
(2) Methods
get: retrieve information about components of a File object’s pathname
getName()、getPath、getAbsolutePath()、getParent()
exists: returns true if the file exists in the file system
canRead: returns true if the file exists and can be read
canWrite: returns true if the file exists and can be written
isFile: returns true if the file is a normal file
isDirectory: returns true if the file is a directory
isAbsolute: returns true if the path is an absolute pathname
public long lastModified(): returns the last modification time

53. The File Class(3)
public long length(): returns the file length in bytes
public boolean mkdir(): Creates a directory, returning true on success
public boolean mkdirs(): Creates all directories in this path,returning true if all were created
public boolean renameTo(File new_name) : Renames a file, returning true if the rename succeeded
public boolean delete() : Deletes the file or directory named in this File object, returning true if the deletion succeeded
public String[] list(): Lists all files in a directory except the equivalent of “.”and “..”

54. The File Class(4)
public String[] list(FilenameFilter filter) :Uses the specified filter to list files in a directory
(3) Note
equals:true if two file objects have the same path , not if they refer to the same underlying file system object
Files are created using FileOutputStream objects or RandomAccessFile objects, not using File objects
The character File.pathSeparatorChar and the string File.pathSeparator represent the character that separates file or directory names in a search path
The path of the file is a protected String field named path.Classes extending File can directly access or modify it as needed

55. Example1
import java.io.*;
public class CopyBytes { public static void main(String[] args) throws IOException { if(args.length != 2)
throw new RuntimeException(“Usage:CopyBytes <src> <dst>”); File inputFile = new File(args[0]); File outputFile = new File(args[1]); FileInputStream in = new FileInputStream(inputFile); FileOutputStream out = new FileOutputStream(outputFile); int c; while ((c = in.read()) != -1) out.write(c); in.close(); out.close(); } }

56. public class FileOperation { public static void main(String[] args)
Example2
import java.io.*;
public class FileOperation { public static void main(String[] args)
{try{
BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
String sdir = “c:\\temp”;
String sfile;
File Fdir1 = new File(sdir);\\创建目录c:\temp
if (Fdir1.exits() && Fidir1.isDirectory()) \\目录存在
{System.out.println(“Directory” + sdir + “exits.” );
for (int I=0; I<Fdir1.list().length; I++) \\列出目录内容
System.out.println((Fdir1.list())[i] );
File Fdir2 = new File(“c:\\temp\\temp”);

57. Fdir2.mkdir(); \\目录不在则创建之 System.out.println();
Example2
if (!Fdir2.exits())
Fdir2.mkdir(); \\目录不在则创建之
System.out.println();
System.out.println(“Now the new list after create a new dir:”);
for (int I=0; I<Fdir1.list().length; I++) \\检查目录是否已建立
System.out.println((Fdir1.list())[i] );}
System.out.println(“Enter a file name in this directory:”);
sfile = in.readLine();
File Ffile = new File(Fdir1, sfile);
if (Ffile.isFile()) \\若此File对象代表文件
{System.out.println(“File” +Ffile.getName() +”in Path” +Ffile.getPath() + “is” +Ffile.getlength() +”in length.”); }
}catch()…

58. RandomAccessFile(1)
The “random access” referred to in the name of the class is the ability to set the read/write file pointer to any position in the file,and perform the operation
You cannot use a RandomAccessFile where either an InputStream or OutputStream object required，but it supports methods of the same names and signatures as their read and write invocations
RandomAccessFile implements both the DataInput and DataOutput interface, so it can be used to read and write bulit-in Java data types
Constructors:
public RandomAccessFile(String name,String mode) throws IOException

59. RandomAccessFile(2)
public RandomAccessFile(File file,String mode) throws IOException
public RandomAccessFile(FileDescriptor fd) throws IOException
(2) Methods
public long getFilePointer() throw IOExcepton
Returns the current location of the file pointer(in bytes) from the beginning of the file
public void seek(long pos) throw IOException
Sets the file pointer to the specified position in number of bytes from the beginning of the file
public long length() throws IOException

60. Characters Streams
Reader and Writer are the abstract superclasses for character streams in java.io
Reader provides the API and partial implementation for readers
--streams that read 16-bit characters
Writer provides the API and partial implementation for writers
--streams that write 16-bit characters

61. Character Stream Classes

62. Subclasses of Reader and Writer
Object
Writer
Reader
BufferedWriter
CharArrayWriter
FilterWriter
OutputStreamWriter
FileWriter
PipedWriter
PrintWriter
BufferedReader
CharArrayReader
FilterReader
PipedReader
InputStreamReader
StringReader
PpushbackReader
LineNumberReader
FileReader
StringWriter

63. The corresponding input/output streams(1)
Reader
InputStream
BufferedReader
BufferedInputStream
LineNumberStream
LineNumberReader
CharArrayReader
ByteArrayInputStream
(none)
InputStreamReader
FileInputStream
FileReader
FilterInputStream
FilterReader
PushbackInputStream
PushbackReader
PipedReader
PipedInputStream
StingReader
StringBufferInputStream

64. The corresponding input/output streams(2)
Writer
OutputStream
BufferedWriter
BufferedOutputStream
CharArrayWriter
ByteArrayOutputStream
OutputStreamWriter
(none)
FileWriter
FileOutputStream
FilterWriter
FilterOutputStream
PrintWriter
PrintStream
PipedWriter
PipedOutputStream
StingWriter
(none)

65. (1) function StreamTokenizer(1)
Tokenizing input data is a common application,and the java.io package provides a StreamTokenizer class for simple tokenization problems
It deals only with the lower 8 bits of Unicode(’\u0000’-‘\u00FF’ )
A stream is tokenized by creatinga StreamTokenizer with an InputStream object as its source, and then setting parameter for the scan. A scanner loop invokes nextToken, which returns the token type of the next token in the stream

66. (2) Token types: StreamTokenizer(2) “ordinary”characters
“special” characters
TT_WORD(-3) :A word was scanned
TT_NUMBER(-2) :A number was scanned
TT_EOL(‘\n’):An end-of-line was found
TT_EOF(-1) : The end-of-file was reached
static double sumStream(Inputstream in)
throws IOException{
StreamTokenizer nums = new StreamTokenizer(in);
double result = 0.0;
while(nums.nextToken() ==StreamTokenizer.TT_NUMBER)
result += nums.nval;
return result; }

67. StreamTokenizer(3)
(3) Method
public void wordChars(int low,int hi)
public void whitespaceChars(int low,int hi)
public void ordinaryChar(int ch)
public void ordinaryChars(int low,int hi)
public void commentChar(int ch)
public void quoteChar(int ch)
public void parseNumbers()
public void resetSyntax()
public void eolIsSignificant(boolean flag)
public void slashStarComments(boolean flag)
public void slashSlashComments(boolean flag)
public void lowerCaseMode(boolean flag)
public void pushback()
public int lineno()
public String toString()

68. Example(1) Import java.io.*; Public class IODemo
Public static void main (String[] args) {
try { //1.Reading input by lines:
if (args.length = = 0) {
BufferedReader stdin = new BufferedReader(
new InputStreamReader(System.in)) ;
System.out.print(“Enter a line:”);
System.out.println(stdin.readLine());
stdin.close(); }
else
BufferedReader in =
new BufferedReader(new FileReader(args[0])) ;
String s, s2 = new String();
While ((s = in.readLine()) != null ) s2 += s + “\n”;
in.close();

69. StringReader in2 = new StringReader (s2); int c;
Example(2)
//2. Input from memory
StringReader in2 = new StringReader (s2);
int c;
While ((c = in2.read()) != -1)
System.out.print((Char)c);
Note: read() returns next byte as an int, so you must cast it as a char

70. Example(3)
//3. Formatted memory input
try {
DataInputStream in3 =
new DataInputStream (
new StringBufferInputStram(s2));
while (true)
System.out.print((char)in3.readByte());
} catch (EOFException e) {
System.out.println(“End of stram”); }

71. Example(4)
try { //4. Line numbering &file output
LineNumberReader li =
new LineNumberReader(
new StringReader(s2));
BufferedRader in4 = new BufferedRader(li);
PrintWriter out1 =
new PrintWriter(new BufferedWriter(
new FileWriter (“IODemo.out”)));
while ((s = in4.readLine()) != null)
out1.println (“Line”+ li.getLineNumber()+s);
out1.close();
} catch (EOFexception e) {
System.out.println(“End of stream”);}

72. Example(5)
//5. Storing & recovering data
try {
DataOutputStream out2 =
new DataOutputStream(
new BufferedOutputStream (“Data.txt”)));
out2.writeDouble( );
out2.writeBytes(“That was pi”); out2.close();
DataInputStream in5 =
new DataInputStream (
new BufferedInputStream(
new FileInputStream(“Data.txt”)));

73. Example(6)
BufferedReader in5br =
new BufferedReader (
new InputStreamReader(in5));
// Must use DataInputStream for data:
System.out.println(in5.readDouble());
//Can now use the “proper” readLine())
System.out.println(in5br.readLine());
} catch (EOFException e) {
System.out.println (“End of Stream”); }

74. Example(7)
//6. Reading and Writing random access file
RandomAccessFile rf =
new RandomAccessFile(“rtest.dat”, “rw”);
for (int i = 0; i <10 ; i++)
rf.writeDouble(i*1.414);
rf.close();
rf = new RandomAccessFile(“rtest.dat”, “rw”);
rf.seek(5*8);
rf.writeDouble( );
rf = new RandomAccessFile(“rtest.dat”, “r”);

75. Example(8)
for (int i = 0; i <10 ; i++)
System.out.println(
“Value” + i + “:” +rf.readDouble());
rf.close();
} catch (FileNotFoundException e) {
System.out.println (
“File Not Found:” + args[1]);
} catch (IOException e) {
System.out.println(“IO Exception”);} }

76. Homework
1.实现一个常用的词统计程序wc（统计任何输入流的字符数、行数和词数）。程序有两种状态，如果没有文件名作参数，程序就使用标准的输入流，如果有一个
或多个文件，程序就依次进行统计。
用FileInputStream实现wc程序
用PushbackInputStream实现wc程序
2. 两个线程，一个是读者，一个是写者，读者取写者所写的内容，双方约定以“.”为信息的结束符。用管道I/O类实现该程序。