Stream IO

General Info

• java.io and java.nio packages.
• Stream class hierarchy.
• Basic Stream classes.
• Input Stream.
• Output Steam.
• Readers and Writers.
• File class.
• RandomAccessFile

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Stream class hierarchy

Two streams: Input and Output.

InputStream
	SequenceInputStream
	PipedInputStream
	FilterInputStream
		DataInputStream
		BufferedInputStream 
		PushbackInputStream
	FileInputStream
	ByteArrayInputStream
	ObjectInputStream

OutputStream
	SequenceOutputStream
	PipedOutputStream
	FilterOutputStream
		DataOutputStream
		BufferedOutputStream 
		PushbackOutputStream
	FileOutputStream
	ByteArrayOutputStream
	ObjectOutputStream

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Basic Stream Classes

• FileInputStream and FileOutputStream
• BufferedInputStream and BufferOutputStream
• DataInputStream and DataOutputStream
• PipedInputStream and PipedOutputStream

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Input Stream

• int read()
• int read(byte[])
• int read(byte[], int, int)
• void close()
• int available()
• skip(long)
• boolean markSupported()
• void mark(int)
• void reset()
• Read Input Stream example:

   InputStream is = null;
   String datafile = new String("mydir/data.dt");
   byte buffer[] = new byte[24];
   try {
      is = (new URL(getDocumentBase(),datafile)).openStream();
   } catch (Exception e) {
     // MalformedURLException may throw
   }
   try {
      is.read(buffer, 0, buffer.length);
   } catch (IOException e) {
    // 
   }
  

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  Readers and Writers

  • The Java programming language uses Unicode to represent strings and characters.
  • InputStreamReader and OutputStreamWriter convert Unicode to platform-specific code.
  • Chain BufferedReader and BufferedWriter to InputStreamReader and OutputStreamWriter for efficiency.
  • Read String input example:

     import java.io.*;
    
     public class CharInput {
    
         public static void main (String args[]) throws java.io.IOException {
             String s;
             InputStreamReader ir;
             BufferedReader in;
    
             ir = new InputStreamReader(System.in);
             in = new BufferedReader(ir);
    
             while ((s = in.readLine()) != null) {
                   System.out.println("Read: " + s);
             }
         }
     }
    

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  Output Stream

  • void write(int)
  • void write(byte[])
  • void write(byte[], int, int)
  • void close()
  • void flush()

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  File class

  • Read a file

    File myFile;
    myFile = new File("fileName");
    myFile = new File("/", "fileName");
    // more useful if the directory or filename
    // is a variable
    
    File myDir = new File("/");
    myFile = new File(myDir, "fileName");
    

  • File names:

    String getName()
    String getPath()
    String getAbsolutePath()
    String getParent()
    boolean renameTo(File newName)
    

  • File tests:

    boolean exists()
    boolean canWrite()
    boolean canRead()
    boolean isFile()
    boolean isDirectory()
    boolean isAbsolute()
    

  • General file information and utilities:

    long lastModified()
    long length()
    boolean delete()
    

  • Directory utilities:

    boolean mkdir()
    String[] list()
    

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  RandomAccessFile

  • With the file name:

    myRAFile = new RandomAccessFile(String name, String mode);
    

  • With a File object:

    myRAFile = new RandomAccessFile(File file, String mode);
    

  • long getFilePointer()
  • void seek(long pos)
  • long length()

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