I am trying to compile the attached program in javac. I've tested it
under Sun's JDK 1.1.5 on Solaris, Symantec's Visual Cafe (forgot which
version, but it's based on JDK 1.1.3) on Windows NT, and Blackdown's JDK
1.1.6v5 on Linux. All of them give the exact same result:
java.lang.NullPointerException:
at java.util.Hashtable.get(Hashtable.java)
at sun.tools.asm.ConstantPool.put(ConstantPool.java)
at sun.tools.asm.Instruction.collect(Instruction.java)
at sun.tools.asm.Assembler.collect(Assembler.java)
at sun.tools.javac.SourceClass.compileClass(SourceClass.java)
at sun.tools.javac.SourceClass.compile(SourceClass.java)
at sun.tools.javac.Main.compile(Main.java)
at sun.tools.javac.Main.main(Main.java)
The problem appears to be related somehow to the System.out.println
statements, probably the combination of the println's with the ?:
operator. If you take out the println's, then the program compiles fine.
I've sent this in as a bug using Sun's bug-report form, but I've posted
it here because I'm curious to know why javac is having problems with
this. Maybe somebody who has the javac source code has some spare time
to check this out and let us know what's going on. (Note that I have not
tried compiling the code using Sun's JDK 1.1.7.)
Thanks,
Trevor Harmon
import java.awt.*;
import java.awt.image.*;
import java.io.*;
/**
This program converts a GIF image containing font data
to a Motorola 68K assembly source code format.
The GIF image must be in 8-bit (256-color) format.
*/
public class GIF2EPROM
{
private static final int FONT_WIDTH = 16;
private static final int FONT_HEIGHT = 16;
private static final int CHARACTER_COUNT = 10 * 4;
/**
This function takes an RGB (direct color model) image and obtains
its palette information and an array of bytes which are indexes
into the palette. The implementation supports only 8-bit (256 color)
images.
*/
private static void getIndexColorData(Image img, byte[] pixels, byte[] byReds,
byte[] byGreens, byte[] byBlues)
{
Panel dummy = new Panel();
int width = img.getWidth(dummy);
int height = img.getHeight(dummy);
int nPaletteIndex = 0;
int[] nPixels = new int[width * height];
int[] nPalette = new int[256];
PixelGrabber pg = new PixelGrabber(img, 0, 0, width, height, nPixels,
0, width);
try
{
pg.grabPixels();
}
catch (InterruptedException e) {}
// Loop through each pixel in the image...
for (int y = 0; y < height; y++)
{
for (int x = 0; x < width; x++)
{
int nIndex = -1;
// Search for the palette index of the current pixel's
color...
for (int i = 0; i <= nPaletteIndex; i++)
{
if ( nPalette[i] == nPixels[y * width + x] )
{
nIndex = i;
break;
}
}
// If the current pixel's color is not in the palette,
add it
// to the palette.
if ( nIndex == -1 )
{
nPalette[nPaletteIndex] = nPixels[y * width +
x];
nIndex = nPaletteIndex;
nPaletteIndex++;
}
// Change the pixel from a color value to an index
value.
pixels[y * width + x] = (byte) nIndex;
}
}
for (int i = 0; i < 256; i++)
{
int red = (nPalette[i] >> 16) & 0xff;
int green = (nPalette[i] >> 8 ) & 0xff;
int blue = (nPalette[i] ) & 0xff;
byReds[i] = (byte)red;
byGreens[i] = (byte)green;
byBlues[i] = (byte)blue;
}
}
private static String toHexString(int value)
{
String hex = Integer.toHexString(value);
switch (hex.length())
{
case 1: hex = "000" + hex; break;
case 2: hex = "00" + hex; break;
case 3: hex = "0" + hex; break;
}
return "$" + hex.substring(0, 2) + ",$" + hex.substring(2, 4);
}
public static void main(String[] args)
{
if (args.length != 1)
{
System.out.println("Error: Must specify a GIF filename.");
return;
}
Image image = Toolkit.getDefaultToolkit().getImage(args[0]);
if (image == null)
{
System.out.println("Error: Could not read GIF image.");
return;
}
try
{
MediaTracker tracker = new MediaTracker(new Panel());
tracker.addImage(image, 0);
tracker.waitForAll();
}
catch (InterruptedException e)
{
System.out.println("Error: Could not read GIF image.");
}
byte[] pixels = new byte[CHARACTER_COUNT * FONT_WIDTH * FONT_HEIGHT];
byte[] reds = new byte[256];
byte[] greens = new byte[256];
byte[] blues = new byte[256];
BufferedWriter file = null;
getIndexColorData(image, pixels, reds, greens, blues);
try
{
file = new BufferedWriter(new FileWriter("font.x68"));
file.write("\tORG $0000\n\n");
for (int i = 0; i < CHARACTER_COUNT; i++)
{
for (int y = i * FONT_HEIGHT; y < i * FONT_HEIGHT +
FONT_HEIGHT; y++)
{
String binary = "";
int hex = 0;
for (int x = FONT_WIDTH - 1; x >= 0; x--)
{
try
{
binary += pixels[y *
FONT_HEIGHT + x] == 0 ? System.out.print("1") : System.out.print("0");
hex = Integer.parseInt(binary,
2);
}
catch (NumberFormatException e) {}
}
System.out.println();
file.write("\tDB " + toHexString(hex) + "\n");
}
// Create a pad of null bytes to fill in 6 characters
of data.
// This simplifies the character layout so that each
character
// set is in its own 512-byte block.
// (16*4 characters * 32 bytes per character == 2048
bytes)
if ((i + 1) % 10 == 0 && i > 0)
{
for (int j = 0; j < 6 * 16; j++)
{
file.write("\tDB " + toHexString(0) +
"\n");
}
}
}
file.flush();
file.close();
}
catch (IOException e)
{
System.out.println("Error: Could not write to file \"font.x68\"");
}
System.exit(0);
}
}
