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algorithm arraylist remove String duplicates and save to new text file

I am currently writing an algorithm that creates an ArrayList from a .txt file, checks it with a loop for duplicates (where the loop should look like this:
Line one is written to new .txt & boolean found is set to true because the string was already found.
Line 2 is written to new .txt etc.
But if two strings are identical, the duplicate, i.e. the second string should just be ignored and continue with the next one).
public class test {
public static void main(String[] args) throws IOException {
String suche = "88 BETRAG-MINUS VALUE 'M'.";
String suche2 = "88 BETRAG-PLUS VALUE 'P'";
boolean gefunden = false;
File neueDatei = new File("C:\\Dev\\xx.txt");
if (neueDatei.createNewFile()) {
System.out.println("Datei wurde erstellt");
}
if (gefunden == false) {
dateiEinlesen(null, gefunden);
ArrayList<String> arr = null;
inNeueDateischreiben(neueDatei, gefunden, arr, suche, suche2);
}
}
public static void dateiEinlesen(File neueDatei, boolean gefunden) {
BufferedReader reader;
String zeile = null;
try {
reader = new BufferedReader(new FileReader("C:\\Dev\\Test.txt"));
zeile = reader.readLine();
ArrayList<String[]> arr = new ArrayList<String[]>();
while (zeile != null) {
arr.add(zeile.split(" "));
zeile = reader.readLine();
}
System.out.println(arr);
} catch (IOException e) {
System.err.println("Error2 :" + e);
}
}
public static void inNeueDateischreiben(File neueDatei, boolean gefunden, ArrayList<String> arr, String suche2,
String suche22) throws IOException {
FileWriter writer = new FileWriter(suche22);
String lastValue = null;
for (Iterator<String> i = arr.iterator(); i.hasNext();) {
String currentValue = i.next();
if (lastValue != null && currentValue.equals(lastValue)) {
i.remove();
{
writer.write(suche2.toString());
gefunden = true;
}
}
writer.close();
}
}
}

Your variable namings (suche2, suche22) makes reading the code difficult.
Other than that, your writing algorithm looks funny. You only compare adjacent lines while duplicate lines could be anywhere. In addition, writer.write only hits when you find a duplicate. Also how you call it and other things don't look right.
Here are some general steps to write this correctly:
Open the file so you can read it line by line.
Create a file writer
Create a set or dictionary like data structure that enables you to look up items in constant time.
For each line that you read do the following:
Look if the line exists in the dictionary.
If not, write it to the new file
If it already exists in the dictionary, skip to step 4.
Add that line to the dictionary for later comparisons and go to step 4.
When the lines are exhausted close both files.
I suggest, you rewrite your code completely as the current version is very difficult to amend.

Project throwing IOException after readFile method call [duplicate]

This question already has answers here:
What is a stack trace, and how can I use it to debug my application errors?
(7 answers)
Closed 3 years ago.
I'm currently writing a program that will read in a CSV file that contains data about age, height, and weight. My issue is, when I call in the method that reads the file from the main, it throws an IOException. I'm not sure what's causing this, and as this is for a project, I am not allowed to throw an IOException from the main() method. I inserted a output print line to try and spot where the bug occurs, because debug mode in eclipse is not allowing me to do so, and it seems that the error occurs before the readFile() method even starts.
I am extremely rusty in java and code in general, and am taking this class after not touching coding for an extended period of time. I'm not sure exactly where to start to try and debug this IOException.
public class Project1 {
public static void main(String[] args) {
//main method declaring project object
Project1 project = new Project1();
String fileName = project.checkArgs(args);
File blah = null; //temporary name for the file don't pay attention to it
try {
blah = project.getFile(fileName); //gets the file and sets it to variable in main
}
catch (FileNotFoundException e) {
e.printStackTrace();
}
try {
project.readFile(blah, 500); //trying to read in file of 2d array in the readFileMethod
}
catch (IOException i) { //method gets caught here
System.out.println("IOException");
}
}
//readFile METHOD
public String[][] readFile(File file, int numRecords) throws IOException {
//two parameters: file, being read in this method, and numRecords the amount
//of elements in the array (I haven't done anything with numRecords yet and I
//believe this may possibly be the source of the error
Scanner reader = new Scanner(file); //scanner to read in file
//2d array to be passed back to main
String[][] data = new String[numRecords][3];
System.out.println("hi"); //test for IOException, doesn't get to this point
int iteration = 0; //to skip first line of text in csv file
while (reader.hasNextLine()) { //loading in elements to 2d array
iteration++;
if (iteration < 1) {
reader.nextLine();
continue;
}
else {
String list[] = reader.nextLine().trim().split(",");
for (int i = 0; i < numRecords; i++) {
for (int j = 0; j < 3; j++) {
data[i][j] = list[j];
System.out.println(data[i][j]);
}
}
}
}
return data;
}
The program catches the IOException in method main().

I can't find the reason, please provide a stack trace (i.printStackTrace()).
Since you do not use the delimiters of the scanner, you may try another way:
BufferedReader br = new BufferedReader(new FileReader(file), bufferSize);
String line;
if ((line = br.readLine()) != null) {
// process the line
}

Java: Methods, Files, and Arrays

I'm supposed to be coding an app that can read names from a hardcoded text file, save them as a string array, then write those names in a different text file but sorted. I believe I have the first two parts down but I'm confused on how to sort the names then write them into a new file.
These is the actual problem I'm working on:
"Take an input file with 10 names in it (hard coded). Write a program to read the file, save the names in a String array and write into a different file names in sorted order. Use Methods appropriately."
BTW I'm a rookie coder, this is what I have so far.
public static void main(String[] args) throws FileNotFoundException {
// TODO code application logic here
readFile();
saveStringArray();
}
public static void readFile() {
File file = new File("/Users/nicoladaaboul/Desktop/Programming/C++, "
+ "HTML5, Java, PHP/Java/Question2/names.txt");
try {
Scanner sc = new Scanner(file);
while (sc.hasNextLine()) {
String i = sc.next();
}
sc.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
public static void saveStringArray() throws FileNotFoundException {
String token1 = "";
Scanner inFile1 = new Scanner(new File("names.txt")).useDelimiter(",\\s*");
List<String> temps = new ArrayList<String>();
while (inFile1.hasNext()) {
token1 = inFile1.next();
temps.add(token1);
}
inFile1.close();
String[] tempsArray = temps.toArray(new String[0]);
Arrays.sort(tempsArray);
for (String s : tempsArray) {
System.out.println(s);
}
}
public static void sortingNames() {
}
public static void writingFile() throws FileNotFoundException {
PrintWriter writer = new PrintWriter("sortedNames.txt");
writer.close();
}

Its important that you break your problem down into instructions.
1. You need to read the file you can use bufferedReader(code below).
2. Create an array(or arraylist) to store your string values.
3. Then as you read each line, store these values in the array.
4. When finished reading the file you then would pass this array to a function that would sort it(Why does my sorting loop seem to append an element where it shouldn't?).
5. Once sorted you simply write this array, to a file.
BufferedReader br = new BufferReader(new FileReader("name.txt"));
int count = 0;
String line;
String[] names = new String[100];
while((line = br.nextLine()) != null){
names[count] = line;
count++;
}

Keep getting Java exception: NoSuchElementException

I keep getting this same exception when I compile. Can anyone explain why I keep getting this error and what it means or what I need to do?
I would like to know what I am doing wrong for future references.
public static void Second()
{
int n = stringList.listSize();
for(int i=0; i<n-1; i=i+2)
{
System.out.println(stringList.retrieveAt(i) + " " + stringList.retrieveAt(i+1));
}
}
public static void Display()throws IOException, FileNotFoundException
{
Scanner infile = new Scanner(new FileReader("D:\\DataFile.txt"));
StringTokenizer token = new StringTokenizer(infile.nextLine());
StringElement str = new StringElement();
while(infile.hasNext())
{
str.setString(token.nextToken());
stringList.insert(str);
}
stringList.print();
}
The exception:
Exception in thread "main" java.util.NoSuchElementException
at java.util.StringTokenizer.nextToken(StringTokenizer.java:349)
at Programmmmmm.Display(Programmmmmm.java:121)
at Programmmmmm.main(Programmmmmm.java:67)

You're calling token.nextToken() without checking whether there are in fact more tokens in token.
Instead of checking whether there infile has more elements, you should check whether token has more tokens.
Instead of
while (infile.hasNext()) { ...
You should do
while (token.hasMoreTokens()) { ...
See Oracle's Java documentation on StringTokenizer for more information and code examples.

You're crossing the streams.
You're looping over the Scanner, but checking nextToken() on the StringTokenizer.
You aren't following the Sun Java coding standards: method names should start with a lower case letter.
That one method is doing far too much:
Reading a hard coded file path.
Tokenizing each line
Printing a list of strings.
Bad idea.
Try something more like this:
public static List<String> tokenizeTextFile(String path) throws IOException, FileNotFoundException {
List<String> words = new ArrayList<String>();
BufferedReader br = null;
if (path != null && path.length() > 0) {
try {
br = new BufferedReader(new FileReader(path));
String line;
while ((line = br.nextLine()) != null) {
String [] tokens = line.split("\\s+");
for (String token : tokens) {
words.add(token);
}
} finally {
close(br); // add this method.
}
}
return words;
}

Finding line number of a word in a text file using java

I require searching a word in a text file and display the line number using java. If it appears more than once I need to show all the line numbers in the output. Can anyone help me please?

Read the text file using Java class LineNumberReader and call method getLineNumber to find the current line number.
http://docs.oracle.com/javase/7/docs/api/java/io/LineNumberReader.html

Something like this might work:
public ArrayList<Integer> find(String word, File text) throws IOException {
LineNumberReader rdr = new LineNumberReader(new FileReader(text));
ArrayList<Integer> results = new ArrayList<Integer>();
try {
String line = rdr.readLine();
if (line.indexOf(word) >= 0) {
results.add(rdr.getLineNumber());
}
} finally {
rdr.close();
}
return results;
}

You can store this information manually. Whenever you are invoking readline() of your BufferedReader, if you're using such, you can also increment a counter by one. E.g.,
public int grepLineNumber(String file, String word) throws Exception {
BufferedReader buf = new BufferedReader(new InputStreamReader(new DataInputStream(new FileInputStream(file))));
String line;
int lineNumber = 0;
while ((line = buf.readLine()) != null) {
lineNumber++;
if (word.equals(line)) {
return lineNumber;
}
}
return -1;
}