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.
Related
public void writeEnvToCsv(int customerId, ZipOutputStream zos, List<SummaryDetailsResponse> summaryDetailsResponseList, QueryHelper queryHelper) {
//Headers size = size(No of distinct entities) * 2 + 1
final CsvWriter writer = new CsvWriter(new OutputStreamWriter(zos), new CsvWriterSettings());
final String[] headers = new String[summaryDetailsResponseList.get(0).getEntities().size() * 2 + 1];
String header;
int index = 0, i, k;
headers[index++] = Entities;
for (i = 0; i < summaryDetailsResponseList.get(0).getEntities().size(); i++) {
header = summaryDetailsResponseList.get(0).getEntities().get(i).getEntityType();
if (valueMap.get(header) != null) {
header = valueMap.get(header);
}
headers[index++] = header + " " + Count;
headers[index++] = header + "(s)";
}
writer.writeHeaders(headers);
for (index = 0; index < summaryDetailsResponseList.size(); index++) {
final String[] values = new String[summaryDetailsResponseList.get(index).getEntities().size() * 2 + 1];
i = 0;
k = 0;
values[i++] = summaryDetailsResponseList.get(index).getRecordName();
for (; i <= summaryDetailsResponseList.get(index).getEntities().size() * 2; ) {
values[i++] = String.valueOf(summaryDetailsResponseList.get(index).getEntities().get(k).getEntityData().get(0).getTotal());
try {
StringBuilder strConcat = new StringBuilder();
List<String> hostNames = queryHelper.getHostNames(customerId,
String.valueOf(summaryDetailsResponseList.get(index).getEntities().get(k).getEntityData().get(0).getQuery()));
for (String host : hostNames) {
if (strConcat.toString().equals(""))
strConcat.append(host);
else
strConcat.append(", ").append(host);
}
values[i++] = strConcat.toString();
} catch (Exception e) {
e.printStackTrace();
}
k++;
}
writer.writeRow(CSVUtils.escapeCSVRow(values));
}
writer.flush();
}
Basically I want to write UT to verify this function. Can we verify the CSVWriter that it has written correct data for headers and rows or ZipOutputStream in any way.
I was able to verify the records writer has written if I pass writer to the function instead of creating it inside the function but I don't want to do this.
import java.io.*;
import java.util.Random;
public class LargeDataset {
public static void main(String[] args) throws Exception {
File file = new File("src/Salary.txt");
if (file.exists()) {
System.out.print("Sorry this file already exists.");
System.exit(0);
}
String firstName = "";
String lastName = "";
String rank = "";
double salaryRange = 0.0;
for (int i = 1; i <= 1000; i++) {
try (PrintWriter output = new PrintWriter(file))
{
firstName = "FirstName" + i;
lastName = "LastName" + i;
rank = generateRandomRank();
if (rank == "assistant")
salaryRange = generateSalary(50000.00, 80000.00);
else if (rank == "associate")
salaryRange = generateSalary(60000.00, 110000.00);
else
salaryRange = generateSalary(75000.00, 130000.00);
output.printf("%s %s %s $%.2f", firstName, lastName, rank, salaryRange);
output.println();
}
}
}
public static String generateRandomRank() {
String[] rank = {"assistant", "associate", "full"};
Random random1 = new Random();
return rank[random1.nextInt(3)];
}
public static double generateSalary(double minSalary, double maxSalary) {
double randomSalary = minSalary + Math.random() * (maxSalary - minSalary);
return randomSalary;
}
}
Hi everyone. I have a program that generates 1000 lines of text and saves it into a file named Salary. The format of each line is: firstNamei, lastNamei, a random rank, and a random salary that is suited to the rank. However when I run this program it only outputs the 1000th line of the loop. I noticed however, when I don't put the PrintWriter in the try statement and close it after the loop by myself, it runs fine and generates all 1000 lines. Why is it only generating the last line based on how it is right now though?
You should open your PrintWriter once, and then write to it many times from your loop, not the other way around:
try (PrintWriter output = new PrintWriter(file)) {
for (int i = 1; i <= 1000; i++) {
firstName = "FirstName" + i;
lastName = "LastName" + i;
rank = generateRandomRank();
if (rank == "assistant")
salaryRange = generateSalary(50000.00, 80000.00);
else if (rank == "associate")
salaryRange = generateSalary(60000.00, 110000.00);
else
salaryRange = generateSalary(75000.00, 130000.00);
output.printf("%s %s %s $%.2f", firstName, lastName, rank, salaryRange);
output.println();
}
}
You should use the above pattern instead of what you have. If you want an exact fix to your current code, then you may try opening the PrintWriter in append mode:
for (int i=1; i <= 1000; i++) {
try (PrintWriter output = new PrintWriter(new FileOutputStream(file, true)) {
// same logic
}
}
This should also work, because now, even though you create a new PrintWriter for each iteration of the loop (inefficient), you open the underlying file in append mode, so each new line should get written properly.
Every time that you are iterating through your 1000 you are creating a new file
for (int i = 1; i <= 1000; i++) {
try (PrintWriter output = new PrintWriter(file))
...
}
move it before the loop
try (PrintWriter output = new PrintWriter(file)) {
for (int i = 1; i <= 1000; i++) {
}
}
So I'm working on a project for school. I need to record the data from my arrays into Excel and I'm having some trouble. This is part of my experiment class.
public static void exp(Params params) {
Scanner s = new Scanner(System.in);
String temp;
for (temp = ""; temp.isEmpty(); temp = s.nextLine()) {
System.out.println("Enter a directory and filename that you want the results to be saved under.");
System.out.println("(If no directory is specified, results will be in same folder as the jar.)");
}
params.setFileName(temp);
s.close();
System.out.println("Executing...");
long timeArray[] = new long[params.getFinalSize() / params.getIncrement()];
int counter = 0;
SortFacade facade = new SortFacade();
for (int n = params.getInitialSize(); n <= params.getFinalSize(); n += params.getIncrement()) {
System.out.println((new StringBuilder("Array of size: ")).append(n).toString());
long tempTime = 0L;
for (int j = 0; j < params.getNumTrials(); j++) {
System.out.println((new StringBuilder("Trial #")).append(j + 1).toString());
params.generateArrays(n, params.getTypeList());
tempTime += facade.sort(params);
}
timeArray[counter] = tempTime / (long) params.getNumTrials();
counter++;
}
params.setTimeArray(timeArray);
System.out.println("Times for each array size(ms): " + Arrays.toString(timeArray));
System.out.println("Writing to File...");
System.out.println("Complete.");
}
}
Start with Filewriter
Make sure what you write is comma-delimeted and saved as a .csv
Also, take a look at this existing question.
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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.
So I have a text file with items like look like this:
350279 1 11:54 107.15
350280 3 11:55 81.27
350281 2 11:57 82.11
350282 0 11:58 92.43
350283 3 11:59 86.11
I'm trying to create arrays from those values, in which the first values of each line are in an array, the second values of each line are in an array, and so on.
This is all the code I have right now, and I can't seem to figure out how to do it.
package sales;
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class Sales {
public static void main (String[] args) throws FileNotFoundException {
Scanner reader = new Scanner(new File("sales.txt"));
int[] transID = new int[reader.nextInt()];
int[] transCode = new int[reader.nextInt()];
String[] time = new String[reader.next()];
double[] trasAmount = new double[reader.hasNextDouble()];
}
}
It's difficult to build an array this way, because Arrays have fixed size... you need to know how many elements they have. If you use a List instead, you don't have to worry about knowing the number of elements in advance. Try this (note: there is no error checking here!):
public static void main (String[] args) throws FileNotFoundException {
Scanner reader = new Scanner(new File("sales.txt"));
List<Integer> ids = new LinkedList<>();
List<Integer> codes = new LinkedList<>();
List<String> times = new LinkedList<>();
List<Double> amounts = new LinkedList<>();
// Load elements into Lists. Note: you can just use the lists if you want
while(reader.hasNext()) {
ids.add(reader.nextInt());
codes.add(reader.nextInt());
times.add(reader.next());
amounts.add(reader.nextDouble());
}
// Create arrays
int[] idArray = new int[ids.size()];
int[] codesArray = new int[codes.size()];
String[] timesArray = new String[times.size()];
double[] amountsArray = new double[amounts.size()];
// Load elements into arrays
int index = 0;
for(Integer i : ids) {
idArray[index++] = i;
}
index = 0;
for(Integer i : codes) {
codesArray[index++] = i;
}
index = 0;
for(String i : times) {
timesArray[index++] = i;
}
index = 0;
for(Double i : ids) {
amountsArray[index++] = i;
}
}
Use Array list because Arrays have fixed size and using Arraylist you add the elements dynamically
Scanner reader = new Scanner(new File("test.txt"));
List<Integer> transID = new ArrayList<Integer>();
List<Integer> transCode = new ArrayList<Integer>();
List<String> time= new ArrayList<String>();
List<Double> trasAmount = new ArrayList<Double>();
while(reader.hasNext() )
{
transID.add(reader.nextInt());
transCode.add(reader.nextInt());
time.add(reader.next());
trasAmount.add(reader.nextDouble());
}
System.out.println(transID.toString());
System.out.println(transCode.toString());
System.out.println(time.toString());
System.out.println(trasAmount.toString());
Output of the above code
transID [350279, 350280, 350281, 350282, 350283]
transCode [1, 3, 2, 0, 3]
time [11:54, 11:55, 11:57, 11:58, 11:59]
trasAmount [107.15, 81.27, 82.11, 92.43, 86.11]
You'll need a while loop to check for input. Since not all inputs are integers you might do something like:
while(reader.hasNextLine()){ //checks to make sure there's still a line to be read in the file
String line=reader.nextLine(); //record that next line
String[] values=line.split(" "); //split on spaces
if(values.length==4){
int val1=Integer.parseInt(values[0]); //parse values
int val2=Integer.parseInt(values[1]);
String val3=values[2];
double val4=Double.parseDouble(values[3]);
//add these values to your arrays. Might have to "count" the number of lines on a first pass and then run through a second time... I've been using the collections framework for too long to remember exactly how to work with arrays in java when you don't know the size right off the bat.
}
}
In addition to my comment here are 3 ways how you cant do it
read into single arrays
int size = 2;
// first allocate some memory for each of your arrays
int[] transID = new int[size];
int[] transCode = new int[size];
String[] time = new String[size];
double[] trasAmount = new double[size];
Scanner reader = new Scanner(new File("sales.txt"));
// keep track of how many elements you have read
int i = 0;
// start reading and continue untill there is no more left to read
while(reader.hasNext()) {
// since array size is fixed and you don't know how many line your file will have
// you have to reallocate your arrays when they have reached their maximum capacity
if(i == size) {
// increase capacity by 5
size += 5;
// reallocate temp arrays
int[] tmp1 = new int[size];
int[] tmp2 = new int[size];
String[] tmp3 = new String[size];
double[] tmp4 = new double[size];
// copy content to new allocated memory
System.arraycopy(transID, 0, tmp1, 0, transID.length);
System.arraycopy(transCode, 0, tmp2, 0, transCode.length);
System.arraycopy(time, 0, tmp3, 0, time.length);
System.arraycopy(trasAmount, 0, tmp4, 0, trasAmount.length);
// reference to the new memory by your old old arrays
transID = tmp1;
transCode = tmp2;
time = tmp3;
trasAmount = tmp4;
}
// read
transID[i] = Integer.parseInt(reader.next());
transCode[i] = Integer.parseInt(reader.next());
time[i] = reader.next();
trasAmount[i] = Double.parseDouble(reader.next());
// increment for next line
i++;
}
reader.close();
for(int j = 0; j < i; j++) {
System.out.println("" + j + ": " + transIDList.get(j) + ", " + transCodeList.get(j) + ", " + timeList.get(j) + ", " + trasAmountList.get(j));
}
as you see this is a lot of code.
Better you use lists so get rid of the overhead of reallocation and copying (at leas in your own code)
read into single lists
// instanciate your lists
List<Integer> transIDList = new ArrayList<>();
List<Integer> transCodeList = new ArrayList<>();
List<String> timeList = new ArrayList<>();
List<Double> trasAmountList = new ArrayList<>();
reader = new Scanner(new File("sales.txt"));
int i = 0;
while(reader.hasNext()) {
// read
transIDList.add(Integer.parseInt(reader.next()));
transCodeList.add(Integer.parseInt(reader.next()));
timeList.add(reader.next());
trasAmountList.add(Double.parseDouble(reader.next()));
i++;
}
reader.close();
for(int j = 0; j < i; j++) {
System.out.println("" + j + ": " + transIDList.get(j) + ", " + transCodeList.get(j) + ", " + timeList.get(j) + ", " + trasAmountList.get(j));
}
You see here how small the code went? But but it still can get better...
A line in the sales.txt file seem to constitute data elements of some entity, why not put them in an object ? for that you may write a class named Trans, some think like this:
class Trans {
public int transID;
public int transCode;
public String time;
public double trasAmount;
#Override
public String toString() {
return transID + ", " + transCode + ", " + time + ", " + trasAmount;
}
}
Then you can use this class to hold the data you read from your file and put each object of that class in a list.
reading into a list of objects
reader = new Scanner(new File("sales.txt"));
List<Trans> transList = new ArrayList<>();
int i = 0;
while(reader.hasNext()) {
Trans trans = new Trans();
trans.transID = Integer.parseInt(reader.next());
trans.transCode = Integer.parseInt(reader.next());
trans.time = reader.next();
trans.trasAmount = Double.parseDouble(reader.next());
transList.add(trans);
i++;
}
reader.close();
for(Trans trans : transList) {
System.out.println("" + i++ + ": " + trans);
}
Output of all 3 methods
0: 350279, 1, 11:54, 107.15
1: 350280, 3, 11:55, 81.27
2: 350281, 2, 11:57, 82.11
3: 350282, 0, 11:58, 92.43
4: 350283, 3, 11:59, 86.11
Here is a sample code to read the values from the file and write into an array. Sample code has logic for int array, you can replicate it for other array types as well.
package sales;
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
public class Sales {
public static void main (String[] args) throws IOException {
FileInputStream fstream = new FileInputStream("sales.txt");
BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
String strLine;
while ((strLine = br.readLine()) != null) {
String[] tokens = strLine.split(" ");
int[] transID = convertStringToIntArray(tokens[0]);
for(int i = 0 ; i < transID.length ; i++ )
System.out.print(transID[i]);
}
}
/** function to convert a string to integer array
* #param str
* #return
*/
private static int[] convertStringToIntArray(String str) {
int intArray[] = new int[str.length()];
for (int i = 0; i < str.length(); i++) {
intArray[i] = Character.digit(str.charAt(i), 10);
}
return intArray;
}
}