below part of program i've written iterate through file find , compare 2 seperate numbers.
it searches each line start point line equal "[device|sensors|checksum]". looks first , second occurrences of "value", gets hex number on line, converts type long. if these 2 long numbers equal we're good, otherwise report problem
here's extract of file i'm using
address(18) = 0x0053 page(18) = sensor value(19) = 0x1 desc(19) = used bytes high priority task address(19) = 0x0053 byte_no(19) = 2 page(19) = sensor ;end of section [device|sensors|stack] [device|sensors|checksum] address(18) = 0x0053 page(18) = sensor value(2) = 0xe0a64f36 address(18) = 0x0053 page(18) = sensor default(19) = 0x00 value(3) = 0xe0a64f36 page(18) = sensor desc(19) = used bytes high priority task ;end of section [device|sensors|checksum] i cannot find wrong code despite trying debug already. loops i've used seem sound.
try { {//read line check if line "[device|sensors|checksum]" while line isn't ";end of section [device|sensors|checksum]" line = reader.readline();//reads lines "[device|sensors|checksum]" if (line.equals("[device|sensors|checksum]")) { //if line "[device|sensors|checksum]" //(check if line "value") else read next line {// read line , (check if line "value") while line doesn't contain "value" line = reader.readline();//reads line first "value" if (line.contains("value")) { // if line "value" retrieve necessary value // else read next line hex1 = line.split("=")[1].trim(); l1 = long.parselong(hex1.substring(2), 16); jframe frame1 = new jframe("joptionpane showmessagedialog example"); joptionpane.showmessagedialog(frame1, "value has hex number\n " + hex1 + "\n\n , integer\n" + l1 + "\n"); system.out.println("here's line read " + line); system.out.println("here's hex number line " + hex1); system.out.println("here's integer hex number " + l1 + "\n"); break; } } while (!"value".contains(line = reader.readline()));//while2 line = reader.readline(); //reads line after first "value" has been found {// read line , check if line has "value" while line doesn't contain "value" line = reader.readline();//reads lines second "value" if (line.contains("value")) { // if line "value" retrieve necessary value // else read next line hex2 = line.split("=")[1].trim(); l2 = long.parselong(hex2.substring(2), 16); jframe frame2 = new jframe("joptionpane showmessagedialog example"); joptionpane.showmessagedialog(frame2, "value has hex number\n " + hex2 + "\n\n , integer\n" + l2 + "\n"); system.out.println("here's line read " + line); system.out.println("here's hex number line " + hex2); system.out.println("here's integer hex number " + l2 + "\n"); break; } } while (!"value".contains(line = reader.readline())); } } while (!";end of section [device|sensors|checksum]".equals(line = reader.readline())); if (l1 == l2) { joptionpane.showmessagedialog(null, "both checksum values equal!"); int status1 = 0; system.exit(status1); } else { joptionpane.showmessagedialog(null, "both checksum values not equal"); int status2 = 0; system.exit(status2); } } catch (ioexception e) { system.out.println("io exception. not read file!"); } edit
the output , stack trace npe
run: here's line read value(2) = 0xe0a64f36 here's hex number line 0xe0a64f36 here's integer hex number 3768995638 exception in thread "main" java.lang.nullpointerexception @ robertskostalproject.checksumfinder.hexfinder(checksumfinder.java:32) @ robertskostalproject.checksumgui.askdirectory(checksumgui.java:43) @ robertskostalproject.robertskostalproject.main(robertskostalproject.java:18) build stopped (total time: 11 seconds)
since haven't specified where "in 2nd while loop" npe, i'll quote bufferedreader#readline():
returns: string containing contents of line, not including line-termination characters, or null if end of stream has been reached
additionally, you're using frame2 variable haven't seen initialized.
