I'm getting dead code warning in eclipse from the if(line == null) statement to the r.close() statement.
BufferedReader r = new BufferedReader(new InputStreamReader(new FileInputStream(file), "UTF-8"));
int counter = 0;
while(true)
{
String line = r.readLine();
counter++;
if(line.contains(" = "))
{
String[] keyVal = new String[2];
keyVal[0] = line.substring(0, line.indexOf(" = ") - 1);
keyVal[1] = line.substring(line.indexOf(" = ") + 3);
buffer.add(keyVal);
}
else
{
new Exception("Invalid expression at line " + counter + " in file " + file.getPath()).printStackTrace();
}
if(line == null) // dead code here
{
break;
}
}
System.out.println("here is a dead code");
r.close(); // another dead code
You are operating on line with if(line.contains(" = ")). If line was null, a NullPointerException would be thrown, which you are not catching. Therefore, the break; statement can't be reached. If the if(line == null) statement is reached, it's not null. Logically, break; will never be executed, so it's unreachable. It appears that Eclipse is detecting this. Note that this will still compile with javac just fine; this is just Eclipse's warning.
Furthermore, if the break; is unreachable, then there is no way to end while(true), so anything beyond the while block is unreachable. So Eclipse warns on this too.
The usual way of reading a file line-by-line, checking the line for null to indicate end of the stream, is
String line;
while ( (line = r.readLine() ) != null)
{
// rest of processing here
}
It's not the cleanest code, with an assignment in the same expression as an equality check, but it's the usual way of doing this kind of read-and-check operation.
This way the while statement can end normally, and then there is no need to check for null later. That also makes any code following the while block reachable.
Put
if(line == null)
{
break;
}
before the
if(line.contains(" = "))
reason it is a dead code is because both if else statements can result in an exception , making any code after that a dead code.
Related
While reading files in Java, I should break the process if there are empty lines in between. But this condition should be ignored if the empty lines are at the end of the file.
while ((line = reader.readLine()) != null) {
if (line == null || line.trim().length() <= 0) {
log.debug("Terminating on first blank line");// terminate on first blank line
empty_line = true;
break;
}
}
The problem with the code above is that it breaks even when the empty lines are at the end of the file which should not happen. How do I do this?
You must break the process when reading a NOT blank line after having read a blank line.
bool blankLineRead = false;
while ((line = reader.readLine()) != null) {
//Inside the cicle line is surely not null
if (line.trim().lenght() <= 0)
blankLineRead = true;
else
if (blankLineRead) {
log.debug("Terminating on first blank line");// terminate on first blank line
break;
}
}
I am trying to iterate through a CSV file in Java. It iterates through the entire file, but will get to the end of the file and try to read the next blank line and throw an error. My code is below.
public class Loop() {
public static void main(String[] args) {
BufferedReader br = null;
String line = "";
try {
HashMap<Integer, Integer> changeData = new HashMap<Integer, Integer>();
br = new BufferedReader(new FileReader("C:\\xxxxx\\xxxxx\\xxxxx\\the_file.csv"));
String headerLine = br.readLine();
while ((line = br.readLine()) != null) {
String[] data = line.split(",");
/*Below is my latest attempt at fixing this,*/
/*but I've tried other things too.*/
if (data[0].equals("")) { break; }
System.out.println(data[0] + " - " + data[6]);
int changeId = Integer.parseInt(data[0]);
int changeCv = Integer.parseInt(data[6]);
changeData.put(changeId, changeCv);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
Like I typed, this works fine until it gets to the end of the file. When it gets to the end of the file, I get the error Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 at com.ucg.layout.ShelfTableUpdates.main(ShelfTableUpdates.java:23). I've stepped through the code by debugging it in Spring Tool Suite. The error comes up whenever I try to reference data[0] or data[6]; likely because there is nothing in that line. Which leads me back to my original question of why it is even trying to read the line in the first place.
It was my understanding that while ((line = br.readLine()) != null) would detect the end of the file, but it doesn't seem to be. I've tried re-opening the file and deleting all of the blank rows, but that did not work.
Any idea how I can detect the end of the file so I don't get an error in this code?
ANSWER:
Credit goes to user #quemeraisc. I also was able to replace the commas with blanks, and if the line then equals null or "", then you know that it is the end of the file; in my case, there are no blank rows before the end of the file. This still does not solve the problem of detecting the end of the file in that if I did have blank rows in between my data that were not the EOF then this would detect those.
Solution 1:
if (data.length < 7) {
System.out.println(data.length);
break;
}
Solution 1:
if (line.replace(",", "").equals(null) || line.replace(",", "").equals("")) {
System.out.println(line.replace(",", ""));
break;
}
Just skip all blank lines:
while ((line = br.readLine()) != null) {
if( line.trim().isEmpty() ) {
continue;
}
....
....
The last line may contain some control characters (like new line, carriage return, EOF and others unvisible chars), in this case a simple String#trim() doesn't remove them, see this answer to know how to remove them: How can i remove all control characters from a java string?
public String readLine() will read a line from your file, even empty lines. Thus, when you split your line, as in String[] data = line.split(","); you get an array of size 1.
Why not try :
if (data.length >= 7)
{
System.out.println(data[0] + " - " + data[6]);
int changeId = Integer.parseInt(data[0]);
int changeCv = Integer.parseInt(data[6]);
changeData.put(changeId, changeCv);
}
which will make sure there are at least 7 elements in your array before proceeding.
To skip blank lines you could try:
while ((line = reader.readLine()) != null) {
if(line.length() > 0) {
String[] data = line.split(",");
/*Below is my latest attempt at fixing this,*/
/*but I've tried other things too.*/
if (data[0] == null || data[0].equals("")) { break; }
System.out.println(data[0] + " - " + data[6]);
int changeId = Integer.parseInt(data[0]);
int changeCv = Integer.parseInt(data[6]);
changeData.put(changeId, changeCv);
}
}
Instead of replace method use replaceAll method. Then it will work.
From third party daily reports i will be getting a similar kind of csv file as shown below
07-Jan-2016
It is better to lead from behind and to put others in front, especially when you celebrate victory when nice things occur. You take the front line when there is danger. Then people will appreciate your leadership.
The main thing that you have to remember on this journey is, just be nice to everyone and always smile.
My requirement is that i need to put each paragraph (A line after space) each quote for above reference in a separate StringBuffer
My question how can i check for empty line ??
I tried with
if(line.contains(" "))
{
System.out.println("hjjjjjjjjjjjjjjjjk");
}
But the above is causing issue where ever there is a space
I am reading the csv file as shown below
String csvFile = "ip/ASRER070116.csv";
BufferedReader br = null;
String line = "";
try {
br = new BufferedReader(new FileReader(csvFile));
while ((line = br.readLine()) != null) {
if (line.startsWith(",")) {
line = line.replaceFirst(",", "");
}
System.out.println(line);
}
}
Could you please tell me how to resolve this ??
if (line != null && (line.trim().equals("") || line.trim().equals("\n"))){
System.out.println("this is empty line");
}
I would suggest you use trim() on the read line and then check if line.length == 0
You can use StringUtils.isBlank method from Apache Commons Lang
public static boolean isBlank(CharSequence cs)
Checks if a CharSequence is whitespace, empty ("") or null.
StringUtils.isBlank(null) = true
StringUtils.isBlank("") = true
StringUtils.isBlank(" ") = true
StringUtils.isBlank("bob") = false
StringUtils.isBlank(" bob ") = false
So I tracked down the bugger, but I am no closer to understanding what is wrong. Here is what the compiler says:
Exception in thread "main" java.lang.NullPointerException at
BasicFile.Search(BasicFile.java:215) at
TestFile.main(TestFile.java:42)
Line 215 is the one that starts with while, first one.
String Search(String key) throws IOException {
int lines = 0;
String line = "";
String foundAt = "";
BufferedReader BF = new BufferedReader(new FileReader(f));
try {
while ((line = BF.readLine().toLowerCase()) != null) {
lines++;
//create tokenizer words with what is in line
StringTokenizer words = new StringTokenizer(line);
while(words.hasMoreTokens()) { //while words has tokens left
//go to next token and compare to key
if (words.nextToken().equals(key.toLowerCase()))
foundAt = foundAt + "\n" + lines + ":" + line;
//do nothing continue loop
}
}
BF.close();
} catch(FileNotFoundException e) {
}
return foundAt;
}
When your buffer reader runs out of lines it returns null. You are trying to call toLowerCase method on null which ends up throwing the null pointer exception.
Refactor your code in a way that it doesn't require you to execute toLowerCase before ensuring the line is non-null.
For example:
String next;
while ((next = BF.readLine()) != null) {
String line = next.toLowerCase();
// ...
}
while ((line = BF.readLine().toLowerCase()) != null)
What happens if BF.readline() returns null?
remove .toLowerCase() from the test
Please, stop it, your code is giving me cancer! There are a number of stylistic errors in the code that you need to fix.
First off in java, method names always begin with a lowercase letter. You are programming in Java, not C#, so you need to use the Java naming conventions. That means your method should be called search, not Search.
The same goes for variable names. What is BF supposed to mean, anyway? Replace it with in, please.
Next up, unless this method is in an object that itself represents that particular file, the global variable f should be passed as a parameter instead.
BufferedReader is AutoCloseable, so you should use a try-with-resources to deal with closing it.
You need to add a javadoc comment to it, documenting its parameters with #param, its return with #return, and exactly why it might need to throw an IOException with #exception.
Here is a mostly-fixed version of your code:
/**
* Needs Javadoc
*/
String search(String key, File f) throws IOException {
int lines = 0
String line = "";
String foundAt = "";
try(BufferedReader in = new BufferedReader(new FileReader(f)) {
while ((line = in.readLine().toLowerCase()) != null) { //the line in question
lines++;
StringTokenizer words = new StringTokenizer(line);
while(words.hasMoreTokens())
if (words.nextToken().equals(key.toLowerCase()))
foundAt = foundAt + "\n" + lines + ":" + line;
}
} catch(FileNotFoundException e){}
return foundAt;
}
Now, the problem here is that in.readline() returns a null sometimes. Calling a method on a null is always a NullPointerException. Therefore you get a NullPointerException when you attempt to call that null's missing toLowerCase() method.
You need to convert it toLowerCase after you ensure it is non-null.
I have a Code where I am scanning the lines using Scanner Class and looping till there are no lines left.
My code looks like this:
File file = new File(filePath);
if (file.exists()) {
Scanner s = new Scanner(file);
String tmp = null;
int result = 0;
try {
while (true) {
tmp = s.nextLine();
if (tmp != null && tmp.equals("")) {
result += Integer.parseInt(tmp);
}
System.out.println(runSequence(Integer.parseInt(tokens[0])));
}
} catch (Exception e) {
e.printStackTrace();
}
System.out.println(result);
}
It gives the error at
tmp = s.nextLine();
java.util.NoSuchElementException: No line found
Which is odd because earlier the same code was working fine.
Why is this line giving an error?
Edit:
My mistake i did not state the question correctly, i particularly left the try catch block out of the while loop so that i could make an exit when the lines ended...My question is why am i not able to read any of the lines...i have about 3-4 lines to read in the txt file and it is not reading any and giving exception at the first line read itself...
I think the better way to code is to have a condition in your while loop using Scanner#hasNextLine(). Scanner#hasNextLine() would make sure that code inside while would only run if it has a line in the file=.
while (s.hasNextLine()) {
tmp = s.nextLine();
if (tmp != null && tmp.equals("")) {
result += Integer.parseInt(tmp);
}
if (tmp != null && tmp.equals(""))
should be (if you are trying to check given string is not empty string)
if (tmp != null && !tmp.isEmpty())
I think you reach at the end of file where there is no remaining line and your condition is while(true) so it tries to read that time also . So you getting NoSuchElementException(if no line was found )
So better to change your while loop as
while (s.hasNextLine()){
tmp = s.nextLine();
// then do something
}
while (s.hasNextLine())
{
//...
}