Beginning Java 2, SDK 1.4 Edition

Last paragraph: delete the line "For more instructions on how to enroll, please see Appendix F at the back of this book."

Last paragraph, 2nd line: change "runon" to "run on"

In the code "private bool hatOn = false;" should be "private boolean hatOn = false;"

Third line in the second paragraph after the diagram whould read: "The class has four instance variables, owner, type, size, and hatOn, and this last variable is always initialized as false."

The code has three variables declared at the beginning which should be:

The second algorithm for the While loop has a mistake. The arrow below the Test condition box should be pointing down and not upwards.

In the code there is an extra } bracket after System.out.println(i);

Line 2 should read as "assert false : "daysInMonth has the value " + daysInMonth;" (there should be a white space after "value").

In the diagram the arrow should also poit to the newly created array.

In the code, remove the } bracket after: "temperature [i][j] = (float)(45.0*Math.random() - 10.0);".

The third last paragraph. It is \unnn and not \Unnn. Also, delete line "The U can be upper or lower case" and replace with "The u can only be in lower case".

Last paragraph: Remove the sentence "However, if you try to compile a program containing this statement you will get an error."

Change the heading "Running from a Method" to "Returning from a Method"

In the second paragraph after the diagram the sentence should read: "Now we have a Sphere object with a radius of 10.0 located at the coordinates (1.0, 1.0, 1.0)."

Add the following statement to the code for the Sphere() constructor in the middle of the page:

In the table near the top of the page, for n<0, n=0, and n>0, the characters after x should all be in superscript (raised-to). The ones in error are:

Last paragraph: The sentence "For more information on the use of the JAR tool to create .jar archives, see Appendix A." should be removed.

The last paragraph, third last line, it should read "Flea object from the myPet data member" and not thePet.

In the diagram the order of the class boxex is wrong. It should be Animal ->Dog->Spaniel and not Dog->Animal->Spaniel. Also, "Spanial" should be "Spaniel"

The sentence below the illustration should read:
"This shows two polylines, one defined by four points, the other defined by six points."

The diagram at the top contains a representation of a PolyLine class with the code 'ListPoint and; ListPoint start;' This should be read as, 'ListPoint end; ListPoint start;'

The PolyLine constructor contains superfluous code. The addPoint() method already takes care of the start and end manipulations so they aren't needed in the constructor. It therefore can be coded like this:

Because the addPoint() method takes care of the start and end manipulations the constructor at the top of the page can be coded more simply as follows:

The line at the bottom of the page is part of the comment. This should be on the line above:

Line 18: It should be "Chapter 13" instead of "Chapter 10".

Line 36: It should be "Chapter 15" instead of "Chapter 11".

The code for method1() in the diagram should be:

The last sentence on the page should read:
"This will show the user that the value cannot be displayed within the specified width."

The 2nd and 7th line of code from the top of the page should be:

The last line of code on this page and the bit on the next page should be changed to:

The last comment line on the page should be deleted.

The following line of code should be inserted immediately before the last for loop:

The line of code towards the bottom of the page should be: File remoteFile = new File(new URI("http://p2p.wrox.com/java"));

The code fragment : File myFile = new File ("dir" + separator + "output.txt"); should read as : File myFile = new File("dir" + File.separator + "output.txt");

The first two sentences should be replaced by:
"This statement creates a File object encapsulating a pathname string that is just the name "output.txt". This will be interpreted as being the name of a file in the current directory when the File object is used. Unless it has been changed programmatically, the current directory will be the directory that was current when program execution was initiated."

The third sentence in the last paragraph should read:
"For a File object created from a relative path string consisting of just the name of the file, the getParent() method will return null."

The following import statement in the example is not required and should be deleted:

The example on this page works under MS Windows but fails under Linux. To make the example work in both environments replace the last line of the do-while loop with:

In the bottom diagram on the page the captions are incorrect.
IntBuffe capacity = 2r should be IntBuffer capacity = 2
Char Buffer capacity = 6 should be CharBuffer capacity = 6

Instead of "DoubleBuffer doubleBuf=buf.asCharBuffer();" it should be "DoubleBuffer doubleBuf = buf.asDoubleBuffer();"

The location of the position arrow in the diagram is incorrect. It should point to the first empty element as the text describes and have the value 6.

The last line of code on the page should be:

On page 422, Line 2, the following sentence,
' We insert the length as type double in the view buffer, longBuf. '
Should be read as follows:
' We insert the length as type double in the view buffer, doubleBuf '

In the code at the bottom of the page, the following line should be deleted:

The sentence in the middle of the page that reads:
"We will also need an array of type byte[] to hold the string characters - remember, we wrote the string as bytes, not Unicode characters."
should be replaced by the sentences:
"We will also need an array of type byte[] to hold the string characters. Remember, we wrote the string as Unicode characters so we must allow 2 bytes for each character in the original string."

The code does not account for the fact that string characters were written to the file by the example on P421 as Unicode and therefore occupy two bytes. The code at the top of the page should be:

Because of the change on P445, the code at the top of this page should be:

The replenish() method is unnecessarily complicated and is not required for the example that follows - once corrected. Thus the second paragraph on the page, the code that follows it, and the paragraph following the code can be deleted.

import java.io.FileInputStream;
import java.io.IOException;
import java.io.File;
import java.io.FileNotFoundException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;

public class ReadPrimesMixedData
{
  public static void main(String[] args)
  {
    File aFile = new File("C:/Beg Java Stuff/primes.txt");
    FileInputStream inFile = null;
    
    try
    {
      inFile = new FileInputStream(aFile);
    }
    catch(FileNotFoundException e)
    {
      e.printStackTrace(System.err);
      System.exit(1);
    }
    
    FileChannel inChannel = inFile.getChannel();
    
    try
    {
      ByteBuffer buf = ByteBuffer.allocateDirect (1024);
      buf.position(buf.limit());  //Set the position for the loop operation
      int strLength = 0;  //Stores the string length
      byte[] strChars = null; //Stores a reference to an array to hold the string
      while(true)
      {
        if(buf.remaining() < 8)
        {
          //Verify enough bytes for string length
          if(inChannel.read(buf.compact()) == -1)
            break;
          buf.flip();
        }
        
        strLength = (int)buf.getDouble();
        
        if(buf.remaining() < 2*strLength)
        {
          //Verify enough bytes for complete string
          if(inChannel.read(buf.compact()) == -1)
            break;
          buf.flip();
        }
        
        strChars = new byte[2*strLength];
        buf.get(strChars);
        
        if(buf.remaining() < 8)
        {
          //Verify enough bytes for prime value
          if(inChannel.read(buf.compact()) == -1)
            break;
          buf.flip();
        }
        
        System.out.println("String length: " + strChars.length + "  String: " +
            ByteBuffer.wrap( strChars ).asCharBuffer() + "  Binary value: " + buf.getLong());
      }
      
      System.out.println("\nEOF reached.");
      inFile.close(); //Close the file and the channel
      
    }
    catch(IOException e)
    {
      e.printStackTrace(System.err);
      System.exit(1);
    }
    
    System.exit(0);    
  }
}

To take account of the code changes on P449, the second paragraph in the How It Works Section should be changed to:

"Within the loop we first check whether there are sufficient bytes for the double value specifying the string length. On the first iteration, this will definitely not be the case so the compact() method will be called to compact the buffer and the reference to buf that is returned will be passed to the read() method for inChannel read data from the file. We then flip the buffer and get the length of the string. Of course, data in the file should be in groups of three items - string length, string, binary prime value - so the end-of-file should be detected trying to obtain the first of these by the read() method for the channel returning -1. In this case we exit the loop by executing a break statement."

The output will be presented better, particularly under Linux if the newline is written after each group of 5 primes. To do this, the output statement can be changed to:

The buffer is unnecessarily large. The statement allocating the buffer should be changed to:

MappedByteBuffer buf = ioChannel.map( FileChannel.MapMode.READ_WRITE, 0L, ioChannel.size() ).load();

import java.io.*;
import java.nio.*;
import java.nio.channels.FileChannel;

public class MemoryMappedFile
{
  public static void main(String[] args)
  {
    File aFile = new File("C:/Beg Java Stuff/primes.bin");
    RandomAccessFile ioFile = null;
    
    try
    {
      ioFile = new RandomAccessFile(aFile,"rw");
    }
    catch(FileNotFoundException e)
    {
      e.printStackTrace(System.err);
      System.exit(1);
    }
    FileChannel ioChannel = ioFile.getChannel();
    final int PRIMESREQUIRED = 10;
    long[] primes = new long[PRIMESREQUIRED];
    
    int index = 0;  //Position for a prime in the file

    final long REPLACEMENT = 999999L; //Replacement for a selected prime
    
    try
    {
      final int PRIMECOUNT = (int)ioChannel.size()/8;
      MappedByteBuffer buf =
        ioChannel.map( ioChannel.MAP_RW, 0L, (int)ioChannel.size() ).load();
      for(int i = 0 ; i < PRIMESREQUIRED ; i++)
      {
         index = 8*(int)(PRIMECOUNT*Math.random());
         primes[i] = buf.getLong(index);
         buf.putLong(index, REPLACEMENT );
      }
      
      StringBuffer str = null;
      
      for(int i = 0 ; i&tl;PRIMESREQUIRED ; i++)
      {
        str = new StringBuffer("           ").append(primes[i]);
        System.out.print( str.substring(str.length() - 12, str.length()) +
          ((i + 1) % 5 == 0 ? "\n" : ""));
      }
      ioFile.close(); // Close the file and the channel
    }
    catch(IOException e)
    {
      e.printStackTrace(System.err);
      System.exit(1);
    }
    System.exit(0);
  }
}

The last sentence in exercise 3 "You can get and set the file position from the underlying file input stream object" should be replaced by "You can't get the file position in an object stream in the same way as you can with a channel. However, you can use the sequence number for an object as the index - the first object being 1, the second being 2, and so on."

In Chapter 12 Exercise 4, the last sentence should be changed to "When an IndexEntry is found, you use the sequence number it contains to retrieve the appropriate Person object."

the code should be re-written as follows

In the table the next method should be written as nextInt(int limit).

The Code on the bottom of this page should be read as follows:

"java.swing" should be "javax.swing" in the figure.

In the figure, the third and top-most pane should say "contentPane object" and not "constantPane obejct".