《输入与输出 》PPT课件.ppt

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1、第八章 输入与输出,概念Java I/O类Java I/O操作标准输入/输出文件读写操作目录管理随机访问文件,概念,数据流：一组有顺序的有起点和终点的字节集合。以流(stream)的方式对数据进行操作,I/O来源 控制台(console)打印/读入 文件(file)读/写 网络接口(TCP/UDP端口)读/写,概念,读/写流的一般流程读(Reading)open a stream/打开读出流while more information/判断 read information/读close the stream/关闭流写(Writing)open a stream/打开写入流while more

2、 information/判断 write information/写close the stream/关闭流,概念,两种流的定义(读取信息的基本数据单位)字节流(byte stream):一个字节(8-bit)一个字节读/写字符流(character stream):一个字符一个字符读/写eg“j a v a 语 言”以字节流的方式读:读8次，8个字节 以字符流的方式读:读6次，6个字符,Java I/O类,字节流的读/写操作(来自JDK1.0)(抽象类)public abstract int read()public int read(byte b)public int read(byte

3、 b,int offset,int length)到达流的终点，无数据读出则返回-1(抽象类)public abstract void write(int b)public void write(byte b)public void write(byte b,int offset,int length)所有的读/写函数都抛出,Java I/O类,字符流的读/写操作(来自JDK1.1)(抽象类)public int read()public int read(char cbuf)publc abstract int read(char cbuf,int offset,int length)到达流

4、的终点，无数据读出则返回-1(抽象类)public void write(int c)public void write(char cbuf)public void write(char cbuf,int offset,int length)所有的读/写函数都抛出,Java I/O类,I/O流的层次关系class 的子类class class java.io.FileInputStreamclass class java.io.BufferedInputStreamclass class class class class class class,Java I/O类,I/O流的层次关系clas

5、s 的子类class class java.io.FileOutputStreamclass class java.io.BufferedOutputStreamclass class class class,Java I/O类,I/O流的层次关系class 的子类class java.io.BufferedReaderclass class class class class class java.io.FileReaderclass class,Java I/O类,I/O流的层次关系class 的子类class java.io.BufferedWriterclass class class

6、 class java.io.FileWriterclass class class,Java I/O类,I/O流的分类(12个功能类),Java I/O类,I/O流的分类(12个功能类),Java I/O类,I/O流的分类(12个功能类),标准输入/输出,System.in System.out System.err 1()2 print(参数),println(参数),class Test public static void main(String args)System.out.println(“Hello World!”);import;class Test public stati

7、c void main(String args)throws IOException byte b=new byte10;System.out.println(Received number=+System.in.read(b);,C:java TestAReceived number=3C:,【示例8-1】IOExample.Java,import Java.io.IOException;class IOExample public static void main(String args)throws IOExceptionchar a;System.out.print(Please in

8、put a char:);a=(char)System.in.read();System.out.println(The char is:+a);,程序运行结果：Please input a char:(键入任意一个字符（C），回车)输出：The number is:C,8.3 常用的流类,文件管理File类,File类包含许多用于执行文件常规操作的方法。可以访问指定文件的所有属性，还可以删除，创建，更名指定的文件或目录。类:文件和目录的路径名路径名(pathname)UNIX平台上绝对路径的前缀“/”，相对路径无前缀，例“/etc/inetd.conf”、“inetd.conf”Window

9、s平台，绝对路径名的前缀由“盘符:”组成，或共享名前缀“”，然后是主机名和共享名，相对路径名无盘符，例“c:windowsnotepad.exe”、“192.168.1.10Test.java”构造方法public File(String pathname)public File(String parent,String child)public File(File parent,String child)parent通常表示一个目录，child则表示一个目录或文件,文件管理File类,常用方法public String getAbsolutePath()public boolean canW

10、rite()/canRead()public boolean renameTo(File dest)public boolean delete()public boolean exists()public String getName()public String getParent()public boolean isDirectory()public boolean isFile()public String list()public String list(FilenameFilter filter)public boolean mkdir()public URL toURL(),文件管

11、理File类,方法举例,import;public class DirList public static void main(String args)File path=new File(.);String list=path.list();for(int i=0;i list.length;i+)System.out.println(listi);,import;import;public class DirList public static void main(String args)File path=new File(.);String list=path.list(new Dir

12、Filter(args0);for(int i=0;i list.length;i+)System.out.println(listi);,class DirFilter implements FilenameFilter String key;DirFilter(String key)this.key=key;public boolean accept(File dir,String name)String f=new File(name).getName();return f.indexOf(key)!=-1;,接口 public boolean accept(File dir,Strin

13、g name);/是否指定的文件应包含在文件列表中,public String getName()in/获得文件或目录名,文件读写操作,文件读/写流程打开文件流条件判断读出/写入关闭文件流两种类型文件FileInputStream/FileOutputStream(字节流)FileReader/FileWriter(字符流),字节流构造方法public FileInputStream(String name)throws FileNotFoundExceptionpublic FileInputStream(File file)throws FileNotFoundExceptionpubli

14、c FileOutputStream(File file)throws FileNotFoundExceptionpublic FileOutputStream(File file,boolean append)throws FileNotFoundException/是否向已存在的文件后添加public FileOutputStream(String name)throws FileNotFoundExceptionpublic FileOutputStream(String name,boolean append)throws FileNotFoundException,文件读写操作,文件

15、读写操作,2.字节流方法public int read()throws IOExceptionpublic int read(byte b)throws IOExceptionpublic int read(byte b,int offset,int len)throws IOExceptionpublic void close()throws IOException public void write(int b)throws IOExceptionpublic void write(byte b)throws IOExceptionpublic void write(byte b,int

16、offset,int len)throws IOException,典型的读文件程序import;import;public class FileInputDemo public static void main(String args)throws IOException FileInputStream file=new FileInputStream(args 0);int c;while(c=file.read()!=-1)System.out.print(char)c);file.close();,import;import;import;import;public class Cop

17、yBytesDemo1 public static void main(String args)throws IOException File inputFile=new File(args0);File outputFile=new File(args1);FileInputStream in=new FileInputStream(inputFile);FileOutputStream out=new FileOutputStream(outputFile);int c;while(c=in.read()!=-1)out.write(c);in.close();out.close();,i

18、mport java.io.*;public class c8_7 public static void main(String args)char c;int c1;File filePath=new File(temp);if(!filePath.exists()filePath.mkdir();File fl=new File(filePath,d1.txt);try FileOutputStream fout=new FileOutputStream(fl);(请输入字符,输入结束按#:);while(c=()!=#)fout.write(c);fout.close();System.

19、out.println(n打印从磁盘读入的数据);,FileInputStream fin=new FileInputStream(fl);while(c1=fin.read()!=-1)System.out.print(char)c1);fin.close();catch(FileNotFoundException e)System.err.println(e);catch(IOException e)System.err.println(e);,运行结果如下:请输入字符，输入结束按 abcd#打印从磁盘读入的数据 abcd#,【示例8-2】FileOutputDemo.Java,impor

20、t;import;import;import;import;public class FileOutputDemo public static void main(String args)throws IOException File fileSource=new File(output.txt);File fileTarget=new File(intput.txt);FileOutputStream target=new FileOutputStream(fileTarget);FileInputStream source=new FileInputStream(fileSource);i

21、nt c;while(c=source.read()!=-1)target.write(c);target.close();source.close();,文件读写操作,字符流构造方法public FileReader(File file)throws FileNotFoundExceptionpublic FileReader(String fileName)throws FileNotFoundExceptionpublic File(String pathname)public FileWriter(File file)throws IOExceptionpublic FileWrite

22、r(File file,boolean append)throws IOExceptionpublic FileWriter(String fileName)throws IOExceptionpublic FileWriter(String fileName,boolean append)throws IOException,import java.io.*;public class Copy public static void main(String args)throws IOException File inputFile=new File(“original.txt);File o

23、utputFile=new File(“result.txt);FileReader in=new FileReader(inputFile);FileWriter out=new FileWriter(outputFile);int c;while(c=in.read()!=-1)out.write(c);in.close();out.close();,FileReader in=new FileReader(“original.txt);FileWriter out=new FileWriter(“result.txt);,public int read()throws IOExcepti

24、onpublic int read(char cbuf)throws IOExceptionpublic int read(char cbuf,int off,int len)throws IOException,public void write(int b)throws IOExceptionpublic void write(char cbuf)throws IOExceptionpublic void write(char cbuf,int off,int len)throws IOException,DataInputStream和DataOutputStream,概述类public

25、 DataInputStream(InputStream in)public final boolean readBoolean()public final byte readByte()public final char readChar()public final int readInt()类public DataOutputStream(OutputStream out)public final void writeBoolean(boolean v)public final void writeByte(int v)public final void writeChar(int v)p

26、ublic final void writeInt(int v),DataOutputStream out=new DataOutputStream(new FileOutputStream(invoice1.txt);double prices=19.99,9.99;int units=12,8;String descs=Java T-shirt,Java Mug;for(int i=0;i prices.length;i+)out.writeDouble(pricesi);out.writeChar(t);out.writeInt(unitsi);out.writeChar(t);out.

27、writeChars(descsi);out.writeChar(n);out.close();,19.99 12 Java T-shirt9.99 8 Java Mug,DataInputStream in=new DataInputStream(new FileInputStream(invoice1.txt);double total;try while(true)double price=in.readDouble();in.readChar();int unit=in.readInt();in.readChar();char chr;StringBuffer desc=new Str

28、ingBuffer(20);while(chr=in.readChar()!=n)desc.append(chr);System.out.println(Youve ordered+unit+units of+desc+at$+price);total=total+unit*price;catch(EOFException e)System.out.println(For a TOTAL of:$+total);in.close();,用于跟踪中间流的类PushbackInputStream,构造方法：PushbackInputStream(InputStream in)PushbackInp

29、utStream(InputStream in,int size)代表方法：Void unread(int n)回退一个字节,BufferedInputStream/BufferedOutputStream,构造方法public BufferedInputStream(InputStream in)2048 bytespublic BufferedInputStream(InputStream in,int size)public BufferedOutputStream(OutputStream out)512 bytespublic BufferedOutputStream(OutputS

30、tream out,int size)public BufferedReader(Reader in)8192 bytespublic BufferedReader(Reader in,int sz)public BufferedWriter(Writer out)8192 bytepublic BufferedWriter(Writer out,int sz),String filename=“test.txt”;FileInputStream fis=new FileInputStream(filename);int count=0;int c;while(c=fis.read()!=-1

31、)if(c=A)count+;fis.close();System.out.println(count);,String filename=“test.txt”;FileInputStream fis=new FileInputStream(filename);BufferedInputStream bis=new BufferedInputStream(fis);int count=0;int c;while(c=bis.read()!=-1)if(c=A)count+;fis.close();System.out.println(count);,BufferedInputStream/Bu

32、fferedOutputStream,数据的读写,随机访问文件,随机访问文件(Random Access File)类读写操作在同一个类中完成，须在构造对象时指定参数通过移动文件指针(file pointer)在文件的指定位置进行读写操作构造方法public RandomAccessFile(String name,String mode)throws FileNotFoundExceptionpublic RandomAccessFile(File file,String mode)throws FileNotFoundExceptionmode:“r”,“rw”,随机访问文件,方法publ

33、ic int read()public int read(byte b)public int read(byte b,int off,int len)public final boolean readBoolean()/readByte()/readChar()/readShort()/readInt()/readDouble()/readFloat()public final String readLine()public void write(int b)public void write(byte b)public void write(byte b,int off,int len)pu

34、blic final void writeBoolean()/writeByte()/writeChar()/writeShort()/writeInt()/writeDouble()/writeFloat(),随机访问文件,方法public void seek(long pos)throws IOExceptionpublic int skipBytes(int n)throws IOExceptionpublic long getFilePointer()throws IOExceptionpublic long length()throws IOExceptionvoid setLeng

35、th(long newLength),import;import;import;public class RAFDemo public static void main(String args)try RandomAccessFile rf=new RandomAccessFile(test.dat,rw);for(int i=0;i 10;i+)rf.writeDouble(i*1.48);rf.close();rf=new RandomAccessFile(test.dat,rw);rf.seek(5*8);rf.writeDouble(47.0001);rf.close();rf=new

36、 RandomAccessFile(test.dat,r);for(int i=0;i 10;i+)System.out.println(Value+i+:+rf.readDouble();rf.close();catch(FileNotFoundException e)System.out.println(e);catch(IOException e)System.out.println(e);,管道类,在两个线程间建立数据流的通道PipedInputStream类创建输入管道PipedOutputStream类创建输出管道管道类的模型,两个继承体系之间的类的对应关系,Filter两个继承体

37、系之间类的对应关系,FileReader和FileWriter,FileReader构造方法public FileReader(String fileName)throws FileNotFoundException public FileReader(File file)throws FileNotFoundExceptionFileWriter构造方法public FileWriter(File file)throws IOExceptionpublic FileWriter(File file,boolean append)throws IOExceptionpublic FileWri

38、ter(String fileName)throws IOExceptionpublic FileWriter(String fileName,boolean append)throws IOException,import java.io.*;public class CopyCharDemo public static void main(String args)throws IOException File inputFile=new File(args0);File outputFile=new File(args1);FileReader in=new FileReader(inpu

39、tFile);FileWriter out=new FileWriter(outputFile);int c;while(c=in.read()!=-1)out.write(c);in.close();out.close();,字节流向字符流的转化,InputStreamReader的构造函数public InputStreamReader(InputStream in)public InputStreamReader(InputStream in,String charsetName)throws UnsupportedEncodingExceptionpublic InputStreamR

40、eader(InputStream in,Charset cs)public InputStreamReader(InputStream in,CharsetDecoder dec),字节流向字符流的转化,OutputStreamWriter的构造函数public OutputStreamWriter(OutputStream out)public OutputStreamWriter(OutputStream out,String charsetName)throws UnsupportedEncodingExceptionpublic OutputStreamWriter(OutputStream out,Charset cs)public OutputStreamWriter(OutputStream out,CharsetEncoder enc),