Develop Reference

Set boolean to true, but filewriter still overwrites the file, any advice?

I have created a simple program that sorts integers in an input file using different algorithms. I also use filewriter to output results to another file. Unfortunately no matter how I change my code, file gets overridden. Any advice?
Been searching for answer on google and tried changing the way I input the syntax but nothing works.
important bits:
setting the writer up
try {
FileWriter fileWriter = new FileWriter ("Sorted output.txt");
//BufferedWriter bufferedWriter = new BufferedWriter (fileWriter);
PrintWriter out = new PrintWriter (new FileWriter("Sorted output.txt", true));
outputting to the file
out.println("User's own data set sorted using bubble sort.");
out.println(unsortedArray + Arrays.deepToString(FileOne));
out.println("Sorted Array looks like this:" + Arrays.toString(intArrayBubble));
out.println(timeToSort + bubbleSortIs + bubbleTime + "ms");
it works fine, however its used in a do while loop, with nested if statements, and each one overrides the other.
Rest of code in case its required - UPDATED - still not working
import java.io.*;
import java.util.*;
import java.util.concurrent.TimeUnit;
public class PDD_Sorting {
public static void main (String [] pArgs)
{
//Array for a file
String[] FileOne;
FileOne = new String[0];
int optionOne = 1,
optionTwo = 2,
optionThree = 3,
secondaryOptionOne = 1,
secondaryOptionTwo = 2,
secondaryOptionThree = 3,
userSelection,
subUserSelection;
String unsortedArray = "Unsorted array is: ",
bubbleSort = "Sorted array using bubble sort: ",
selectionSort = "Sorted array using selection sort: ",
insertionSort = "Sorted array using insertion sort: ",
timeToSort = "Time needed to sort this array using ",
bubbleSortIs = "bubble sort is ",
selectionSortIs = "selection sort is ",
insertionSortIs = "insertion sort is ",
welcomeToSorter = "Welcome to the SORTER - program that can sort your txt files containing integeres in an ascending order!",
notFiles = "Integers, not files :)",
pleaseSelect = "Please select one of the following options, by enetering a number asociated with it.",
optionOneUserInput = "1. Sort your own data set - input your own set of data (integers, separated by colons, no spaces) into the Input file.",
optionTwoPredefined = "2. Use predetermind set of data to test the algorythms.",
optionThreeExit = "3. Exit the program.",
subMenuPleaseSelect = "Please select which algorythm would you like to use to sort this file.",
optionBubble = "(1) - Bubble Sort.",
optionSelection = "(2) - Selection Sort.",
optionInsertion = "(3) - Insertion Sort.",
usersDataBubble = "User's own data set sorted using bubble sort.",
sortedArrayLooks = "Sorted Array looks like this:",
msTime = "ms",
usersDataSelection = "User's own data set sorted using selection sort.",
usersDataInsertion = "User's own data set sorted using insertion sort.",
validOption = "Please enter a valid option i.e. 1,2 or 3",
lessThanZero = "If time shown in ms is 0, that means the time needed to conduct the sort is shorter than 1ms.",
fileCreated = "File created.",
terminatingProgram = "Terminating the program.",
unableToWriteFile = "Unable to write to file";
System.out.println(welcomeToSorter);
System.out.println(notFiles);
Scanner tInput = new Scanner (System.in);
try {
FileWriter fileWriter = new FileWriter ("Sorted output.txt");
//BufferedWriter bufferedWriter = new BufferedWriter (fileWriter);
PrintWriter out = new PrintWriter (new FileWriter("Sorted output.txt", true));
do {
System.out.println(pleaseSelect);
System.out.println(optionOneUserInput);
System.out.println(optionTwoPredefined);
System.out.println(optionThreeExit);
// Scanner tInput = new Scanner (System.in);
userSelection = tInput.nextInt();
if (userSelection == optionOne) {
//System.out.println("Please enter a valid path for your file.");
String[] splitFile = null;
//String userFile = tInput.next();
FileOne = getAndPrepareFile(splitFile);
System.out.println(subMenuPleaseSelect);
System.out.println(optionBubble);
System.out.println(optionSelection);
System.out.println(optionInsertion);
subUserSelection = tInput.nextInt();
if (subUserSelection == secondaryOptionOne) {
int size = FileOne.length;
int [] intArrayBubble = new int [size];
for(int i=0; i<size; i++) {
intArrayBubble[i] = Integer.parseInt(FileOne[i]);
}
bubbleSort(intArrayBubble);
long bubbleTime = timeCount(intArrayBubble);
out.println(usersDataBubble);
out.println(unsortedArray + Arrays.deepToString(FileOne));
out.println(sortedArrayLooks + Arrays.toString(intArrayBubble));
out.println(timeToSort + bubbleSortIs + bubbleTime + msTime);
}
else if (subUserSelection == secondaryOptionTwo) {
int size2 = FileOne.length;
int [] intArraySelection = new int [size2];
for(int i=0; i<size2; i++) {
intArraySelection[i] = Integer.parseInt(FileOne[i]);
}
doSelectionSort(intArraySelection);
long selectionTime = timeCount(intArraySelection);
out.println(usersDataSelection);
out.println(unsortedArray + Arrays.deepToString(FileOne));
out.println(sortedArrayLooks + Arrays.toString(intArraySelection));
out.println(timeToSort + selectionSortIs + selectionTime + msTime);
}
else if (subUserSelection == secondaryOptionThree) {
int size3 = FileOne.length;
int [] intArrayInsertion = new int [size3];
for(int i=0; i<size3; i++) {
intArrayInsertion[i] = Integer.parseInt(FileOne[i]);
}
doInsertionSort(intArrayInsertion);
long insertionTime = timeCount(intArrayInsertion);
out.println(usersDataInsertion);
out.println(unsortedArray + Arrays.deepToString(FileOne));
out.println(sortedArrayLooks + Arrays.toString(intArrayInsertion));
out.println(timeToSort + insertionSortIs + insertionTime + msTime);
}
else {
System.out.println(validOption);
tInput.next();
}
}
else if (userSelection == optionTwo){
//file being prepared and loaded via function
String[] splitFilePredefined = null;
FileOne = getAndPrepareFilePredefined(splitFilePredefined);
//converting string array into int array so the method can sort it.
int size = FileOne.length;
int [] intArrayBubble = new int [size];
for(int i=0; i<size; i++) {
intArrayBubble[i] = Integer.parseInt(FileOne[i]);
}
int size2 = FileOne.length;
int [] intArraySelection = new int [size2];
for(int i=0; i<size2; i++) {
intArraySelection[i] = Integer.parseInt(FileOne[i]);
}
int size3 = FileOne.length;
int [] intArrayInsertion = new int [size3];
for(int i=0; i<size3; i++) {
intArrayInsertion[i] = Integer.parseInt(FileOne[i]);
}
//inserting pre-prepared int arrays into variables including a timecount method
int bubbleTime = timeCount(intArrayBubble);
int selectionTime = timeCount(intArraySelection);
int insertionTime = timeCount(intArrayInsertion);
//sorting array using various sorts
bubbleSort(intArrayBubble);
doSelectionSort(intArraySelection);
doInsertionSort(intArrayInsertion);
//out.println("Sorted arrray using insertion sort looks like this: " + Arrays.toString(intArrayInsertion));
out.println(timeToSort + bubbleSortIs + bubbleTime + "ms");
out.println(timeToSort + selectionSortIs + selectionTime + "ms");
out.println(timeToSort + insertionSortIs + insertionTime + "ms");
out.println(lessThanZero);
System.out.println(fileCreated);
}
else if (userSelection == optionThree){
System.out.println(terminatingProgram);
System.exit(0);
}
else {
System.out.println(validOption);
tInput.next();
}
out.flush();
out.close();
//tInput.close();
}while (userSelection != optionThree);
}
catch (Exception e)
{
System.out.println(unableToWriteFile);
tInput.next();
}
tInput.close();
}//end main
//method that fetches the file from predefined, hardcoded location and removes comas, esentially prepares the file for the next phase
private static String[] getAndPrepareFile (String[] splitFile)
{
Scanner fileIn = null;
try
{
fileIn = new Scanner(new FileInputStream("C:\\Users\\Greg\\Documents\\Programming\\PDD - Assignment 1\\Input.txt"));
String fileNew = fileIn.next();
splitFile = fileNew.split(",");
//System.err.println(Arrays.toString(splitFile)); //Arrays.toString needed to print the array correctly, otherwise it prints the address of the object
fileIn.close();
}
catch (IOException e)
{
System.out.println("File not found.");
//System.exit(0);
}
return splitFile;
}
//as above but works for predefined file, that can be generated using randomNumber.java program
private static String[] getAndPrepareFilePredefined (String[] splitFilePredefined)
{
Scanner fileIn = null;
try
{
fileIn = new Scanner(new FileInputStream("C:\\Users\\Greg\\Documents\\Programming\\PDD - Assignment 1\\Generated input.txt"));
String fileNew = fileIn.next();
splitFilePredefined = fileNew.split(",");
//System.err.println(Arrays.toString(splitFile)); //Arrays.toString needed to print the array correctly, otherwise it prints the address of the object
fileIn.close();
}
catch (IOException e)
{
System.out.println("File not found.");
//System.exit(0);
}
return splitFilePredefined;
}
//method used to sort a file using bubble sort
private static void bubbleSort(int[] arr) {
int n = arr.length;
int temp = 0;
for(int i=0; i < n; i++){
for(int j=1; j < (n-i); j++){
if(arr[j-1] > arr[j]){
//swap elements
temp = arr[j-1];
arr[j-1] = arr[j];
arr[j] = temp;
}
}
}
}
//method used to sort a file using selection sort
private static int[] doSelectionSort(int[] arr){
for (int i = 0; i < arr.length - 1; i++)
{
int index = i;
for (int j = i + 1; j < arr.length; j++)
if (arr[j] < arr[index])
index = j;
int smallerNumber = arr[index];
arr[index] = arr[i];
arr[i] = smallerNumber;
}
return arr;
}
//method used to sort a file using sinsertion sort
private static int[] doInsertionSort(int[] input){
int temp;
for (int i = 1; i < input.length; i++) {
for(int j = i ; j > 0 ; j--){
if(input[j] < input[j-1]){
temp = input[j];
input[j] = input[j-1];
input[j-1] = temp;
}
}
}
return input;
}
//method used to calculate how much time has lapsed while using any of the given sort methods, outputs in ms, if less than 1 ms, outputs 0ms
private static int timeCount (int[] anArray)
{
long start = System.nanoTime();
Arrays.sort(anArray);
long end = System.nanoTime();
long timeInMillis = TimeUnit.MILLISECONDS.convert(end - start, TimeUnit.NANOSECONDS);
//System.out.println("Time spend in ms: " + timeInMillis);
return (int) timeInMillis;
}
}//end class
File gets constantly overridden, how do i stop this and make it add to file instead?

You don't need the first FileWriter fileWriter = new FileWriter("Sorted output.txt");; this is actually creating/overwriting the file, after which your PrintWriter opens it again for appending.
So, just change
// ... omitting beginning
try {
FileWriter fileWriter = new FileWriter ("Sorted output.txt");
//BufferedWriter bufferedWriter = new BufferedWriter (fileWriter);
PrintWriter out = new PrintWriter (new FileWriter("Sorted output.txt", true));
do {
// ... omitting rest
to
// ... omitting beginning
try {
//BufferedWriter bufferedWriter = new BufferedWriter (fileWriter);
PrintWriter out = new PrintWriter (new FileWriter("Sorted output.txt", true));
do {
// ... omitting rest

Move out.close() outside the loop
else {
System.out.println("Please enter a valid option i.e. 1,2 or 3");
tInput.next();
}
out.flush();
/* THIS -> out.close(); <- THIS */
//tInput.close();
}while (userSelection != optionThree);
out.close();
}
I tried your code and your problem is not that the file is being overwritten, but that you are closing the outputstream in the first iteration.

join files using scanner

I have 2 files as below :
1.txt
first|second|third
fourth|fifth|sixth
2.txt
first1|second1|third1
fourth1|fifth1|sixth1
Now I want to join them both :
first|first1|second1|third1|second|third
fourth|fourth1|fifth1|sixth1|fifth|sixth
Am trying using scanner but not able to join them. Any suggestion.
Scanner scanner = new Scanner(new File(("F:\\1.txt")));
Scanner scanner2 = new Scanner(new File(("F:\\2.txt")));
while(scanner.hasNext()) {
while(scanner2.hasNext()) {
system.out.println(scanner.next() + "|" + scanner2.next() + "|");
}
// output
first|second|third|first1|second1|third1|
fourth|fifth|sixth|fourth1|fifth1|sixth1|

Scanner scanner = new Scanner(new File(("F:\\1.txt")));
Scanner scanner2 = new Scanner(new File(("F:\\2.txt")));
String[] line1, line2, res;
while (scanner.hasNext() && scanner2.hasNext()) {
line1 = scanner.next().split("\\|");
line2 = scanner2.next().split("\\|");
int len = Math.min(line1.length,line2.length);
res= new String[line1.length + line2.length];
for(int index = 0, counter = 0; index < len; index++){
res[counter++] = line1[index];
res[counter++] = line2[index];
}
if(line1.length > line2.length){
for(int jIndex = 2*line2.length, counter = 0;jIndex < (line1.length+line2.length);jIndex++ ){
res[jIndex] = line1[line2.length + (counter++)];
}
}else if(line2.length > line1.length){
for(int jIndex = 2*line1.length, counter = 0;jIndex < (line1.length+line2.length);jIndex++ ){
res[jIndex] = line2[line1.length + (counter++)];
}
}
String result = Arrays.asList(res).toString().replaceAll("(^\\[|\\]$)", "").replace(", ", "|");
System.out.println(result);
}
scanner.close();
scanner2.close();
You can discard the if conditions if both lines contains same number of tokens
This will give output as,
first|first1|second|second1|third|third1
fourth|fourth1|fifth|fifth1|sixth|sixth1
And
String[] line1, line2, res;
while (scanner.hasNext() && scanner2.hasNext()) {
line1 = scanner.next().split("\\|");
line2 = scanner2.next().split("\\|");
res= new String[line1.length + line2.length];
int counter = 0;
res[counter++] = line1[0];
for(int index = 0; index < line2.length; index++){
res[counter++] = line2[index];
}
for(int index = 1; index < line1.length; index++){
res[counter++] = line1[index];
}
String result = Arrays.asList(res).toString().replaceAll("(^\\[|\\]$)", "").replace(", ", "|");
System.out.println(result);
}
scanner.close();
scanner2.close();
will give output as
first|first1|second1|third1|second|third
fourth|fourth1|fifth1|sixth1|fifth|sixth

List<String[]> method Adding always same values

In my Java Project, i want to read values from txt file to List method.Values seems like;
1 kjhjhhkj 788
4 klkkld3 732
89 jksdsdsd 23
Number of row changable. I have tried this codes and getting same values in all indexes.
What can i do?
String[] dizi = new String[3];
List<String[]> listOfLists = new ArrayList<String[]>();
File f = new File("input.txt");
try {
Scanner s = new Scanner(f);
while (s.hasNextLine()) {
int i = 0;
while (s.hasNext() && i < 3) {
dizi[i] = s.next();
i++;
}
listOfLists.add(dizi);
}
} catch (FileNotFoundException e) {
System.out.println("Dosyaya ba?lanmaya çal???l?rken hata olu?tu");
}
int q = listOfLists.size();
for (int z = 0; z < q; z++) {
for (int k = 0; k < 3; k++) {
System.out.print(listOfLists.get(z)[k] + " ");
}
}

String [] dizi = new String [3];
dizi is a global variable getting overridden eveytime in the loop. Thats why you are getting same values at all indexes
Make a new instance everytime before adding to the list.

You put the same reference to the list, create a new array in while loop.
while (s.hasNextLine()){
String[] dizi = new String[3]; //new array
int i = 0;
while (s.hasNext() && i < 3)
{
dizi[i] = s.next();
i++;
}
listOfLists.add(dizi);
}

The program throws NullPointerException [closed]

Closed. This question needs details or clarity. It is not currently accepting answers.
Want to improve this question? Add details and clarify the problem by editing this post.
Closed 8 years ago.
Improve this question
Not sure why it gives me the NullPointerException. Please help.
I am pretty sure all the arrays are full, and i restricted all the loops not to go passed empty spaces.
import java.util.;
import java.io.;
public class TextAnalysis {
public static void main (String [] args) throws IOException {
String fileName = args[0];
File file = new File(fileName);
Scanner fileScanner = new Scanner(file);
int MAX_WORDS = 10000;
String[] words = new String[MAX_WORDS];
int unique = 0;
System.out.println("TEXT FILE STATISTICS");
System.out.println("--------------------");
System.out.println("Length of the longest word: " + longestWord(fileScanner));
read(words, fileName);
System.out.println("Number of words in file wordlist: " + wordList(words));
System.out.println("Number of words in file: " + countWords(fileName) + "\n");
System.out.println("Word-frequency statistics");
lengthFrequency(words);
System.out.println();
System.out.println("Wordlist dump:");
wordFrequency(words,fileName);
}
public static void wordFrequency(String[] words, String fileName) throws IOException{
File file = new File(fileName);
Scanner s = new Scanner(file);
int [] array = new int [words.length];
while(s.hasNext()) {
String w = s.next();
if(w!=null){
for(int i = 0; i < words.length; i++){
if(w.equals(words[i])){
array[i]++;
}
}
for(int i = 0; i < words.length; i++){
System.out.println(words[i] + ":" + array[i]);
}
}
}
}
public static void lengthFrequency (String [] words) {
int [] lengthTimes = new int[10];
for(int i = 0; i < words.length; i++) {
String w = words[i];
if(w!=null){
if(w.length() >= 10) {
lengthTimes[9]++;
} else {
lengthTimes[w.length()-1]++;
}
}
}
for(int j = 0; j < 10; j++) {
System.out.println("Word-length " + (j+1) + ": " + lengthTimes[j]);
}
}
public static String longestWord (Scanner s) {
String longest = "";
while (s.hasNext()) {
String word = s.next();
if (word.length() > longest.length()) {
longest = word;
}
}
return (longest.length() + " " + "(\"" + longest + "\")");
}
public static int countWords (String fileName) throws IOException {
File file = new File(fileName);
Scanner fileScanner = new Scanner(file);
int count = 0;
while(fileScanner.hasNext()) {
String word = fileScanner.next();
count++;
}
return count;
}
public static void read(String[] words, String fileName) throws IOException{
File file = new File(fileName);
Scanner s = new Scanner(file);
while (s.hasNext()) {
String word = s.next();
int i;
for ( i=0; i < words.length && words[i] != null; i++ ) {
words[i]=words[i].toLowerCase();
if (words[i].equals(word)) {
break;
}
}
words[i] = word;
}
}
public static int wordList(String[] words) {
int count = 0;
while (words[count] != null) {
count++;
}
return count;
}
}

There are two problems with this code
1.You didn't do null check,although the array contains null values
2.Your array index from 0-8,if you wan't to get element at 9th index it will throw ArrayIndexOutOfBound Exception.
Your code should be like that
public static void lengthFrequency (String [] words) {
int [] lengthTimes = new int [9];
for(int i = 0; i < words.length; i++) {
String w = words[i];
if(null!=w) //This one added for null check
{
/* if(w.length() >= 10) {
lengthTimes[9]++;
} else {
lengthTimes[w.length()-1]++;
}
}*/
//Don't need to check like that ...u can do like below
for(int i = 0; i < words.length; i++) {
String w = words[i];
if(null!=w)
{
lengthTimes[i] =w.length();
}
}
}
//here we should traverse upto length of the array.
for(int i = 0; i < lengthTimes.length; i++) {
System.out.println("Word-length " + (i+1) + ": " + lengthTimes[i]);
}
}

Your String Array String[] words = new String[MAX_WORDS]; is not initialized,you are just declaring it.All its content is null,calling length method in line 31 will give you null pointer exception.
`

Simple mistake. When you declare an array, it is from size 0 to n-1. This array only has indexes from 0 to 8.
int [] lengthTimes = new int [9];
//some code here
lengthTimes[9]++; // <- this is an error (this is line 29)
for(int i = 0; i < 10; i++) {
System.out.println("Word-length " + (i+1) + ": " + lengthTimes[i]); // <- same error when i is 9. This is line 37

When you declare:
String[] words = new String[MAX_WORDS];
You're creating an array with MAX_WORDS of nulls, if your input file don't fill them all, you'll get a NullPointerException at what I think is line 37 in your original file:
if(w.length() >= 10) { // if w is null this would throw Npe
To fix it you may use a List instead:
List<String> words = new ArrayList<String>();
...
words.add( aWord );
Or perhaps you can use a Set if you don't want to have repeated words.

Java StringTokenizer

I have the following input
(11,C) (5,) (7,AB)
I need to split them into 2 part for each coordinates.
So my intarray should have 11, 5, 7
and my letter array should have C,,AB
But when I try using stringtokenizer,
I only get my intarray should have 11, 5, 7
and my letter array should have C,AB
Is there any way I could get the empty part of (5,)?
Thank you.
Vector<String> points = new Vector<String> ();
String a = "(11,C) (5,) (7,AB)";
StringTokenizer st = new StringTokenizer(a, "(,)");
while(st.hasMoreTokens()) {
points.add(st.nextToken());
}
}
System.out.println(points);

List <Integer> digits = new ArrayList <Integer> ();
List <String> letters = new ArrayList <String> ();
Matcher m = Pattern.compile ("\\((\\d+),(\\w*)\\)").matcher (string);
while (m.find ())
{
digits.add (Integer.valueOf (m.group (1)));
letters.add (m.group (2));
}

Must be like this
String[] values = a.split("\\) \\(");
String[][] result = new String[values.length][2];
for (int i = 0; i < values.length; i++) {
values[i] = values[i].replaceAll("\\(|\\)", "") + " ";
result[i] = values[i].split("\\,");
System.out.println(result[i][0] + " * " + result[i][1]);
}
result will contain coordinate pairs.

public static void main(String[] args) {
String s = "(11,C), (5,) ,(7,AB)";
ArrayList<String> name = new ArrayList<String>();
ArrayList<Integer> number = new ArrayList<Integer>();
int intIndex = 0, stringIndex = 0;
String[] arr = s.split(",");
for (int i = 0; i < arr.length; i++) {
String ss = arr[i].replace("(", "");
ss = ss.replace(")", "");
boolean b = isNumeric(ss);
// System.out.println( Arrays.toString(arr));
if (b) {
int num = Integer.valueOf(ss.trim()).intValue();
number.add(num);
} else
name.add(ss);
}
System.out.println(name);
System.out.println(number);
}
public static boolean isNumeric(String str) {
try {
double d = Double.parseDouble(str);
} catch (NumberFormatException nfe) {
return false;
}
return true;
}
Try this: I have slightly changed the input from "(11,C) (5,) (7,AB)" to "(11,C), (5,) ,(7,AB)" .
Output:
[C, , AB]
[11, 5, 7]

Brutal coding, in raw level:
List<String> points = new ArrayList<String> ();
String source= "(11,C) (5,) (7,AB)";
StringTokenizer deleteLeft = new StringTokenizer(source, "(");
while(deleteLeft.hasMoreTokens()) {
StringTokenizer deleteRight = new StringTokenizer(deleteLeft.nextToken(), ")");
points.add(deleteRight.nextToken());
}
System.out.println(points);
}