以下是我编写的程序的一部分，用于迭代文件以查找和比较两个单独的数字。
它在每一行搜索该行等于“[Device | Sensors | Checksum]”的起点。然后它会查找第一次和第二次出现的“Value”，获取该行的十六进制数字，将其转换为 long 类型。如果这两个长数相等，我们就会好，否则我们报告一个问题
这是我正在使用的文件的摘录
Address(18) = 0x0053
Page(18) = Sensor
Value(19) = 0x1
Desc(19) = used bytes from 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 from high priority task
;end of section [Device|Sensors|Checksum]
尽管我已经尝试调试它，但我无法找到这段代码的确切错误。我用过的循环似乎很合理。
try {
do {//read line then check if line is "[Device|Sensors|Checksum]" WHILE line isn't ";end of section [Device|Sensors|Checksum]"
line = reader.readLine();//Reads all lines up to "[Device|Sensors|Checksum]"
if (line.equals("[Device|Sensors|Checksum]")) { //IF line is "[Device|Sensors|Checksum]" then
//(check if line is "Value") ELSE read next line
do {// DO read line and (check if line is "Value") WHILE line doesn't contain "Value"
line = reader.readLine();//Reads all line up to first "Value"
if (line.contains("Value")) { // IF line is "Value" then 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 and integer\n" + l1 + "\n");
System.out.println("Here's the line read " + line);
System.out.println("Here's the hex number from the line " + Hex1);
System.out.println("Here's the integer from the hex number " + l1 + "\n");
break;
}
} while (!"Value".contains(line = reader.readLine()));//while2
line = reader.readLine(); //Reads the line AFTER the first "Value" has been found
do {// Read line and check if line has "Value" WHILE line doesn't contain "Value"
line = reader.readLine();//Reads all lines up to second "Value"
if (line.contains("Value")) { // IF line is "Value" then 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 and integer\n" + l2 + "\n");
System.out.println("Here's the line read " + line);
System.out.println("Here's the hex number from the line " + Hex2);
System.out.println("Here's the integer from the 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 ARE 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. Could not read file!");
}
修改
NPE的输出和堆栈跟踪
run:
Here's the line read Value(2) = 0xE0A64F36
Here's the hex number from the line 0xE0A64F36
Here's the integer from the hex number 3768995638
Exception in thread "main" java.lang.NullPointerException
at robertskostalproject.checksumFinder.HexFinder(checksumFinder.java:32)
at robertskostalproject.checksumGUI.askDirectory(checksumGUI.java:43)
at robertskostalproject.RobertsKostalProject.main(RobertsKostalProject.java:18)
BUILD STOPPED (total time: 11 seconds)
答案 0 :(得分：3)
由于你没有在第二个while循环中指定 where “你得到了NPE，我只引用BufferedReader#readLine()：
返回：包含行内容的字符串，不包括任何行终止字符，如果已到达流末尾，则为或null
此外，您使用的是我们尚未见过的frame2变量。
答案 1 :(得分：0)
这就是我现在所拥有的。谢天谢地，没有太多变化，而且很有效！
class checksumFinder {
public static long l1 = 1;
public static long l2 = 0;
//Default to not equal
String HexFinder(JFileChooser inFileName, String line, String Hex1, String Hex2)
throws FileNotFoundException, IOException {
File file = inFileName.getSelectedFile();
BufferedReader reader = new BufferedReader(new FileReader(file));
try {
line = reader.readLine();//Read all lines up to "[Device|Sensors|Checksum]"
do {//Read line then check if line is "[Device|Sensors|Checksum]" WHILE isn't ";end of section [Device|Sensors|Checksum]"
line = reader.readLine();
if (line.equals("[Device|Sensors|Checksum]")) { //IF line is "[Device|Sensors|Checksum]" then
//(check if line is "Value") ELSE read next line
do {// DO read line and check line is "Value" WHILE line doesn't contain "Value"
if (line.contains("Value")) { //IF line is "Value" then 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 and integer\n" + l1 + "\n");
System.out.println("Here's the line read " + line);
System.out.println("Here's the hex number from the line " + Hex1);
System.out.println("Here's the integer from the hex number " + l1 + "\n");
break;
}
} while (!"Value".contains(line = reader.readLine()));//while2
line = reader.readLine(); //Read the line AFTER first "Value" has been found
do {//Read line and check if line has "Value" WHILE line doesn't contain "Value"
if (line.contains("Value")) { // IF line is "Value" then 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 and integer\n" + l2 + "\n");
System.out.println("Here's the line read " + line);
System.out.println("Here's the hex number from the line " + Hex2);
System.out.println("Here's the integer from the hex number " + l2 + "\n");
break;
}
} while (!"Value".contains(line = reader.readLine()));//while3
while (!";end of section [Device|Sensors|Checksum]".equals(line)){
line = reader.readLine();
}
}
} while (!";end of section [Device|Sensors|Checksum]".equals(line)); //while1
if (l1 == l2) {
JOptionPane.showMessageDialog(null, "Both checksum values ARE 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. Could not read file!");
}
return null;
}
}