Printing the wrong text and getting results randomly - processing

Question

Here's my code, where lastLine checks the last of the file:
import java.util.Random;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
public String lastLine( File file ) {
RandomAccessFile fileHandler = null;
try {
fileHandler = new RandomAccessFile( file, "r" );
long fileLength = fileHandler.length() - 1;
StringBuilder sb = new StringBuilder();
for(long filePointer = fileLength; filePointer != -1; filePointer--){
fileHandler.seek( filePointer );
int readByte = fileHandler.readByte();
if( readByte == 0xA ) {
if( filePointer == fileLength ) {
continue;
}
break;
} else if( readByte == 0xD ) {
if( filePointer == fileLength - 1 ) {
continue;
}
break;
}
sb.append( ( char ) readByte );
}
String lastLine = sb.reverse().toString();
return lastLine;
} catch( java.io.FileNotFoundException e ) {
e.printStackTrace();
return null;
} catch( java.io.IOException e ) {
e.printStackTrace();
return null;
} finally {
if (fileHandler != null )
try {
fileHandler.close();
} catch (IOException e) {
/* ignore */
}
}
}
File file = new File("lines.txt");
String last = lastLine(file);
String previous = null;
float r = random(0,255);
float g = random(0, 255);
float b = random(0, 255);
public void settings() {
size(500, 500);
}
public void setup() {
frameRate(60);
stroke(155, 0, 0);
textAlign(CENTER, CENTER);
textSize(30);
background(r+(random(0,100)), g+(random(0,100)), b+(random(0,100)));
}
void draw() {
previous = lastLine(file);
if (last.equals(previous)) {
last = lastLine(file);
}
if (!last.equals(previous)) {
if (last.indexOf("w") != -1) {
text("there is a w", 255, 255);
fill(r, g, b);
}
else {
text("there is not a w", 255, 255);
}
fill(50);
last = lastLine(file);
}
}
So whenever the last line of the file has been changed, the text printed on screen should change to "there is a w" or "there is not a w" depending on whether or not there is a w in the last line. However, I seem to be getting results randomly. For example, when the last string of the file contains a "w," sometimes I get "there is not a w" printed on the screen. I've also gotten "there is a w" for when there is no w in the string.
What did I do wrong?

Answer 1

Your code is doing some strange things: why are you reading in the file 3 separate times in the draw() function? Why are you reading in the file one byte at a time?
Instead of trying to go through your code, here is an example that seems to do what you want:
String previous;
void draw() {
String current = lastLine();
if (!current.equals(previous)) {
background(random(255), random(255), random(255));
if (current.contains("w")) {
text("YES W", 0, 50);
} else {
text("NO W", 0, 50);
}
}
previous = current;
}
public String lastLine() {
String lines[] = loadStrings("list.txt");
if(lines.length == 0){
return "";
}
return lines[lines.length-1];
}
Also note that if you're not going to be deploying as JavaScript, you might want to use Java's file watch service instead of reading in the file every frame.