I'm printing a single string from a server which contains multiple '\n' in it and would like to clear the screen before each new message. However, the following code causes the screen to be cleared after each line in the single string.
while (true) {
String s = server.readLine();
if (s == null) {
throw new NullPointerException();
}
ConsoleCleaner.clean();
System.out.println(s.toString());
}
Again, s is one single string with multiple '\n' inside which leads to one line being printed and the screen cleared each time.
I'm assuming that server is a BufferedReader here, since you haven't specified otherwise. And for the purpose of BufferedReader.readLine(), there's no such thing as "a single string with multiple \n". When the method encounters the first \n, that's the output of readLine().
You could avoid this issue by keeping track of the non-whitespace length of the last message printed, and only clearing the screen when it's non-zero.
Could you adapt this example to reach your requirement?
Read all lines with BufferedReader
Perhaps like this:
String s;
while ((line = server.readLine()) != null) {
s += line + (System.getProperty("line.separator"));
}
ConsoleCleaner.clean();
System.out.println(s.toString());
Not tried this...
Related
public String compWord() throws IOException, ClassNotFoundException
{
// Local constants
final int MAX_COUNT = 8;
// Local variables
BufferedReader reader = new BufferedReader(new FileReader("dictionary.txt")); // Create a new BufferedReader, looking for dictionary.txt
List<String> lines = new ArrayList<String>(); // New ArrayList to keep track of the lines
String line; // Current line
Random rand = new Random(); // New random object
String word; // The computer's word
/********************* Start compWord *********************/
// Start reading the txt file
line = reader.readLine();
// WHILE the line isn't null
while(line != null)
{
// Add the line to lines list
lines.add(line);
// Go to the next line
line = reader.readLine();
}
// Set the computers word to a random word in the list
word = lines.get(rand.nextInt(lines.size()));
if(word.length() > MAX_COUNT)
compWord();
// Return the computer's word
return word;
}
From what I understand it should only be returning words less than 8 characters? Any idea what I am doing wrong? The if statement should recall compWord until the word is less than 8 characters. But for some reason I'm still get words from 10-15 chars.
Look at this code:
if(word.length() > MAX_COUNT)
compWord();
return word;
If the word that is picked is longer than your limit, you're calling compWord recursively - but ignoring the return value, and just returning the "too long" word anyway.
Personally I would suggest that you avoid the recursion, and instead just use a do/while loop:
String word;
do
{
word = lines.get(rand.nextInt(lines.size());
} while (word.length() > MAX_COUNT);
return word;
Alternatively, filter earlier while you read the lines:
while(line != null) {
if (line.length <= MAX_COUNT) {
lines.add(line);
}
line = reader.readLine();
}
return lines.get(rand.nextInt(lines.size()));
That way you're only picking out of the valid lines to start with.
Note that using Files.readAllLines is a rather simpler way of reading all the lines from a text file, by the way - and currently you're not closing the file afterwards...
If the word is longer than 8 characters, you simply call your method again, continue, and nothing changes.
So:
You are getting all the words from the file,
Then getting a random word from the List, and putting it in the word String,
And if the word is is longer than 8 characters, the method runs again.
But, at the end, it will always return the word it picked first. The problem is that you just call the method recursively, and you do nothing with the return value. You are calling a method, and it will do something, and the caller method will continue, and in this case return your word. It does not matter if this method is recursive or not.
Instead, I would recommend you use a non-recursive solution, as Skeet recommended, or learn a bit about recursion and how to use it.
I have the following issue: I am trying to parse a .csv file in java, and store specifically 3 columns of it in a 2 Dimensional array. The Code for the method looks like this:
public static void parseFile(String filename) throws IOException{
FileReader readFile = new FileReader(filename);
BufferedReader buffer = new BufferedReader(readFile);
String line;
String[][] result = new String[10000][3];
String[] b = new String[6];
for(int i = 0; i<10000; i++){
while((line = buffer.readLine()) != null){
b = line.split(";",6);
System.out.println("ID: "+b[0]+" Title: "+b[3]+ "Description: "+b[4]); // Here is where the outofbounds exception occurs...
result[i][0] = b[0];
result[i][1] = b[3];
result[i][2] = b[4];
}
}
buffer.close();
}
I feel like I have to specify this: the .csv file is HUGE. It has 32 columns, and (almost) 10.000 entries (!).
When Parsing, I keep getting the following:
XXXXX CHUNKS OF SUCCESFULLY EXTRACTED CODE
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException:3
at ParseCSV.parseFile(ParseCSV.java:24)
at ParseCSV.main(ParseCSV.java:41)
However, I realized that SOME of the stuff in the file has a strange format e.g. some of the texts inside it for instance have newlines in them, but there is no newline character involved in any way. However, if I delete those blank lines manually, the output generated (before the error message is prompted) adds the stuff to the array up until the next blank line ...
Does anyone have an idea how to fix this? Any help would be greately appreciated...
Your first problem is that you probably have at least one blank line in your csv file. You need to replace:
b = line.split(";", 6);
with
b = line.split(";");
if(b.length() < 5){
System.err.println("Warning, line has only " + b.length() +
"entries, so skipping it:\n" + line);
continue;
}
If your input can legitimately have new lines or embedded semi-colons within your entries, that is a more complex parsing problem, and you are probably better off using a third-party parsing library, as there are several very good ones.
If your input is not supposed to have new lines in it, the problem probably is \r. Windows uses \r\n to represent a new line, while most other systems just use \n. If multiple people/programs edited your text file, it is entirely possible to end up with stray \r by themselves, which are not easily handled by most parsers.
A way to easily check if that's your problem is before you split your line, do
line = line.replace("\r","").
If this is a process you are repeating many times, you might need to consider using a Scanner (or library) instead to get more efficient text processing. Otherwise, you can make do with this.
When you have new lines in your CSV file, after this line
while((line = buffer.readLine()) != null){
variable line will have not a CSV line but just some text without ;
For example, if you have file
column1;column2;column
3 value
after first iteration variable line will have
column1;column2;column
after second iteration it will have
3 value
when you call "3 value".split(";",6) it will return array with one element. and later when you call b[3] it will throw exception.
CSV format has many small things, to implement which you will spend a lot of time. This is a good article about all possible csv examples
http://en.wikipedia.org/wiki/Comma-separated_values#Basic_rules_and_examples
I would recommend to you some ready CSV parsers like this
https://commons.apache.org/proper/commons-csv/apidocs/org/apache/commons/csv/CSVParser.html
String's split(pattern, limit) method returns an array sized to the number of tokens found up to the the number specified by the limit parameter. Limit is the maximum, not the minimum number of array elements returned.
"1,2,3" split with (",", 6) with return an array of 3 elements: "1", "2" and "3".
"1,2,3,4,5,6,7" will return 6 elements: "1", "2", "3", "4", "5" and ""6,7" The last element is goofy because the split method stopped splitting after 5 and returned the rest of the source string as the sixth element.
An empty line is represented as an empty string (""). Splitting "" will return an array of 1 element, the empty string.
In your case, the string array created here
String[] b = new String[6];
and assigned to b is replaced by the the array returned by
b = line.split(";",6);
and meets it's ultimate fate at the hands of the garbage collector unseen and unloved.
Worse, in the case of the empty lines, it's replaced by a one element array, so
System.out.println("ID: "+b[0]+" Title: "+b[3]+ "Description: "+b[4]);
blows up when trying to access b[3].
Suggested solution is to either
while((line = buffer.readLine()) != null){
if (line.length() != 0)
{
b = line.split(";",6);
System.out.println("ID: "+b[0]+" Title: "+b[3]+ "Description: "+b[4]); // Here is where the outofbounds exception occurs...
...
}
or (better because the previous could trip over a malformed line)
while((line = buffer.readLine()) != null){
b = line.split(";",6);
if (b.length() == 6)
{
System.out.println("ID: "+b[0]+" Title: "+b[3]+ "Description: "+b[4]); // Here is where the outofbounds exception occurs...
...
}
You might also want to think about the for loop around the while. I don't think it's doing you any good.
while((line = buffer.readLine()) != null)
is going to read every line in the file, so
for(int i = 0; i<10000; i++){
while((line = buffer.readLine()) != null){
is going to read every line in the file the first time. Then it going to have 9999 attempts to read the file, find nothing new, and exit the while loop.
You are not protected from reading more than 10000 elements because the while loop because the while loop will read a 10001th element and overrun your array if there are more than 10000 lines in the file. Look into replacing the big array with an arraylist or vector as they will size to fit your file.
Please check b.length>0 before accessing b[].
I need to read a text file using java. Not a problem. But I need to reject the empty lines at the end of the file. The file is quite large, around a million or so lines. I need to process each line, one at a time. Even if they are empty.
But, if the empty lines are at the end of the file, then I need to reject it. Note that there can be multiple empty lines at the end of the file.
Any quick solutions? I almost want to write a FileUtility.trimEmptyLinesAndEnd(File input). But I cant help feeling that someone might have written something like this already.
Any help appreciated.
Note:
I have read this link.
Java: Find if the last line of a file is empty.
But this is not what I am trying to do. I need to reject multiple
empty lines.
When you find an empty line, increment a counter for the number of empty lines. If the next line is also empty, increment the counter. If you reach the end of the file, just continue on with what you want to do (ignoring the empty lines you found). If you reach a non-empty line, first do whatever you do to process an empty line, repeating it for each empty line you counted. Then process the non-empty line as normal, and continue through the file. Also, don't forget to reset the empty line counter to zero.
Pseudo code:
emptyLines = 0;
while (the file has a next line) {
if (line is empty) {
emptyLines++;
} else {
if (emptyLines > 0) {
for (i = 0; i < emptyLines; i++) {
process empty line;
}
emptyLines = 0;
}
process line;
}
}
You have to read all lines in your file. You can introduce a guarding that will store the value of last not empty line. At the end return the subset from zero to guardian.
In case you have a stream process.
read line
if empty
increase empty lines counter
else
if there was some empty lines
yield fake empty lines that counter store
reset counter
yield line
Thanks for all the responses. I think both Vash - Damian Leszczyński and forgivenson cracked the pseudocode for this problem. I have taken that forward and am providing here the Java code for people who come looking for an answer after me.
#Test
public void test() {
BufferedReader br = null;
try {
String sCurrentLine;
StringBuffer fileContent = new StringBuffer();
int consecutiveEmptyLineCounter = 0;
br = new BufferedReader(new FileReader("D:\\partha\\check.txt"));
while ((sCurrentLine = br.readLine()) != null) {
// if this is not an empty line
if (!(sCurrentLine.trim().length() == 0)) {
// if there are no empty lines before this line.
if (!(consecutiveEmptyLineCounter > 0)) {
// It is a non empty line, with non empty line prior to this
// Or it is the first line of the file.
// Don't do anything special with it.
// Appending "|" at the end just for ease of debug.
System.out.println(sCurrentLine + "|");
} else {
// This is a non empty line, but there were empty lines before this.
// The consecutiveEmptyLineCounter is > 0
// The "fileContent" already has the previous empty lines.
// Add this non empty line to "fileContent" and spit it out.
fileContent.append(sCurrentLine);
System.out.println(fileContent.toString() + "#");
// and by the way, the counter of consecutive empty lines has to be reset.
// "fileContent" has to start from a clean slate.
consecutiveEmptyLineCounter = 0;
fileContent = new StringBuffer();
}
} else {
// this is an empty line
// Don't execute anything on it.
// Just keep it in temporary "fileContent"
// And count up the consecutiveEmptyLineCounter
fileContent.append(sCurrentLine);
fileContent.append(System.getProperty("line.separator"));
consecutiveEmptyLineCounter++;
}
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {
if (br != null)
br.close();
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
Thanks for all the help.
And, what I have provided here is just one solution. If someone comes across something more clever, please share. I can't shake the feeling off that there should be some FileUtils.trimEmptyLinesAtEnd() sort of method somewhere.
Just read the File backwards. Starting from the first line you read, refrain from processing all blank lines you encounter.
Starting with the first non-blank line you encounter, and thereafter, process all lines whether or not they're blank.
The problem is "intractable" wrt to a neat solution if you read the File forward since you can never know if at some point after a long run of blank lines there might yet be a non-blank line.
If the processing of lines in order, first-to-last, matters, then there is no neat solution and anything like what you have now is about what there is.
I'm trying to create a small program that allows you to search for a word in a text file, and then the program should print out the whole line the text is in.
Example:
test.txt
don't mind this text
don't mind this either
and then when you let the program search for the word "text", it should print out "Don't mind this text".
What's the best way to do this?
This is what I have;
public boolean findFileInCache(){
try (BufferedReader br = new BufferedReader(new FileReader("direct.txt")))
{
while ((name = br.readLine()) != null)
{
Process p = Runtime.getRuntime().exec(name);
}
}
catch (IOException e1) { }
return true;
}
Use BufferedReader to read the file line by line using the BufferedReader.readLine() method.
For each line, check if the word is in it using a regular expression, or by splitting the line into a String[] (using String.split()), and iterating the entries in the resulting array to check if any of them is the desired word. If the desired word is there - print the entire line.
If you chose the 2nd suggestion, don't forget to check equality of two strings by using equals() and NOT by using ==
There are a couple of things you need to do:
Learn the basics by going through an introductory Java book, or course notes, from the beginning, making sure you understand each step as it comes.
Read the Javadocs of likely classes, to find methods that could be useful for the task.
You have already found two core pieces of the solution:
You are getting a line at a time using BufferedReader.readLine()
You are doing it in a while loop, so you handle one line at a time
Now, you need to work out how to deal with each line. Although you didn't include the type, name is a String. It would be better as:
while ((String name = br.readLine()) != null) {
... do something with `line`
}
If your code compiled without String there, it means you declared name as a global. Don't do that, until you know what you're doing.
Breaking things into methods is good; so let's make "do something with line" use a method now:
while ((String name = br.readLine()) != null) {
if(matches(line,"text")) {
System.out.println(line);
}
}
Now you need to write matches():
private boolean matches(String line, String word) {
boolean result = // work out whether it's a match
return result;
}
So, how do you write the guts of matches()?
Well, start by looking at the methods available in String. It has methods like contains() and split(). Some of those methods return other types, like arrays. Your teaching material and reference materials tell you how to look in arrays. The answers are there.
I'm needing to locate a string on a particular line in a text file that is composed of several lines of strings. However, my loop to find the text or the end of the file is eternally searching. I know the string is in the file. Here is the code I am using to locate the text - but be warned, if you try it on your system even with a simple text file it will go into an eternal loop.
I very much appreciate any tips or pointers to explain what I'm doing wrong here.
private static void locateText(String locateText, BufferedReader locateBffer) {
boolean unfound = true;
try
{
String line = locateBffer.readLine();
while (unfound)
{
line = locateBffer.readLine();
if ((line.equals(locateText)) || (line == null))
{
unfound = false;
}
}
}
catch(IOException e)
{
System.out.println("I/O error in locateText");
}
}
Update: Found the problem - it was not finding the match on the first line of the file.
I think GaryF is right (your text is located in the first line of your file).
I wanted to point a line in your code:
if ((line.equals(locateText)) || (line == null)) {
you must instead write this:
if ((line == null) || (line.equals(locateText)) {
Indeed, if line is null, your code will throw a NullPointerException. That's why you must test if line is null before.
In addition to that, I suggest that you have a look in commons.lang library of Apache, as it provides quite usefull classes for text (like StringUtils)...
Is your text to find in the first line, by any chance? You do a readLine operation outside of your loop and then inside, so the first line basically gets ignored.
Change this loop to something like that and it will read all the lines:
while((line = locateBffer.readLine()) != null){
if(line.equals(locateText)){
break;
}
}
Maybe that will help.