I wrote a program to accept input from a text file, and display the words from the file in ascending order with no duplicates. The output is correct if there is no exception thrown. If the exception is thrown, the user is asked for valid input and the initial method is repeated. When this happens, and a valid input is finally entered, the output is duplicated.
I know something is not being reset, but I cannot figure out what it is.
public void go() {
getWords();
System.out.println(wordList);
wordList = new ArrayList<String>(new HashSet<String>(wordList));
Collections.sort(wordList);
System.out.println(wordList);
}
void getWords() {
try {
File file = new File(getInput());
BufferedReader reader = new BufferedReader(new FileReader(file));
String line = null;
while ((line = reader.readLine()) != null) {
addWord(line);
}
} catch(Exception ex) {
System.out.println("Invalid file name, try again.");
go();
}
}
void addWord(String lineToParse) {
String[] tokens = lineToParse.split("\\s");
for(int i = 0; i < tokens.length; i++) {
wordList.add(tokens[i]);
}
}
When you call go() from the catch block, you're forgetting that the original go() invocation is still on the stack. It doesn't disappear just because you've called the method again. Essentially, you're performing some accidental recursion.
So in this case, you'll call go() a second time, it will execute as per normal, then the stack will "unwind" and execute the remainder of the first invocation of the go method, printing out the wordlist, sorting it, then printing it out again.
A quick fix might be to have getWords() return a boolean (false if an exception is thrown), then just change the first line to while(!getWords());.
It's because you are calling go, method inside the catch block which cause printing of the output again, you could correct it like this,
public void go() {
getWords();
System.out.println(wordList);
wordList = new ArrayList<String>(new HashSet<String>(wordList));
Collections.sort(wordList);
System.out.println(wordList);
}
void getWords() {
try {
File file = new File(getInput());
BufferedReader reader = new BufferedReader(new FileReader(file));
String line = null;
while ((line = reader.readLine()) != null) {
addWord(line);
}
} catch(Exception ex) {
System.out.println("Invalid file name, try again.");
getwords(); //Changed
}
}
void addWord(String lineToParse) {
String[] tokens = lineToParse.split("\\s");
for(int i = 0; i < tokens.length; i++) {
wordList.add(tokens[i]);
}
}
Related
I've been searching the web and I can't seem to find a working solution.
I have a file containing theses lines:
Room 1
Coffee
Iron
Microwave
Room_end
Room 2
Coffee
Iron
Room_end
I want to print all Strings between Room 1 and Room_end. I want my code to start when it find Room 1, print line after Room 1 and stop when it get to the first Room_end it find.
private static String LoadRoom(String fileName) {
List<String> result = new ArrayList<>();
try (BufferedReader reader = new BufferedReader(new FileReader(fileName))) {
result = reader.lines()
.dropWhile(line -> !line.equals("Room 1"))
.skip(1)
.takeWhile(line -> !line.equals("Room_end"))
.collect(Collectors.toList());
} catch (IOException ie) {
System.out.println("Unable to create " + fileName + ": " + ie.getMessage());
ie.printStackTrace();
}
for (int i = 0; i < result.size(); i++) {
System.out.println(result.get(i).getname());//error on getname because it cant work with Strings
}
}
class Model {
private String name;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
I am able to get a method to print all Strings of the file but not specific range of Strings. I also tried to work with Stream. My code feel quite messy, but I've been working on it for a while an it seems it only get messier.
I think there is a problem if you want to use lambda expression here:
lambda expressions are functional programming, and functional programming requires immutability, that means there should not be state related issue, you can call the function and give it same parameters and the result always will be the same, but in your case, there should be a state indicating whether you should print the line or not.
can you try this solution? I write it in python, but mainly it is just about a variable should_print that located outside of the scope
should_print = False
result = reader.lines()
for line in result:
if line == "Room end":
break
if should_print:
print(line)
if line == "Room 1":
should_print = True
keep a boolean value outside of the iteration, and check/update the value in each iteration
public static Map<String, List<String>> getRooms(String path) throws IOException {
Map<String, List<String>> result = new HashMap<>();
try (Scanner sc = new Scanner(new File(path))) {
sc.useDelimiter("(?=Room \\d+)|Room_end");
while (sc.hasNext()) {
Scanner lines = new Scanner(sc.next());
String room = lines.nextLine().trim();
List<String> roomFeatures = new ArrayList<>();
while (lines.hasNextLine()) {
roomFeatures.add(lines.nextLine());
}
if (room.length() > 0) {
result.put(room, roomFeatures);
}
}
}
return result;
}
is one way of doing it for your 'rooms file' though it should really be made more OO by making a Room bean to hold the data. Output with your file: {Room 2=[Coffee, Iron ], Room 1=[Coffee, Iron, Microwave]}
Switched my code and used this:
private static String loadRoom(String fileName) {
BufferedReader reader = null;
StringBuilder stringBuilder = new StringBuilder();
try {
reader = new BufferedReader(new FileReader(fileName));
String line = null; //we start with empty info
String ls = System.getProperty("line.separator"); //make a new line
while ((line = reader.readLine()) != null) { //consider if the line is empty or not
if (line.equals("Room 1")) { //condition start on the first line being "Room 1"
line = reader.readLine(); // read the next line, "Room 1" not added to stringBuilder
while (!line.equals("Room_end")) { //check if line String is "Room_end"
stringBuilder.append(line);//add line to stringBuilder
stringBuilder.append(ls);//Change Line in stringBuilder
line = reader.readLine();// read next line
}
}
}
stringBuilder.deleteCharAt(stringBuilder.length() - 1);
} catch (IOException e) {
e.printStackTrace();
} finally {
if (reader != null)
try {
reader.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return stringBuilder.toString();
}
Here's a solution that uses a scanner and a flag. You may choose to break the loop when it reads "Room_end"
import java.util.Scanner;
import java.io.*;
public class Main{
private static String loadRoom(String fileName) throws IOException {
Scanner s = new Scanner(new File(fileName));
StringBuilder sb = new StringBuilder();
boolean print = false;
while(s.hasNextLine()){
String line = s.nextLine();
if (line.equals("Room 1")) print = true;
else if (line.equals("Room_end")) print = false;
else if (print) sb.append(line).append("\n");
}
return sb.toString();
}
public static void main(String[] args) {
try {
String content = loadRoom("content.txt");
System.out.println(content);
}catch(IOException e){
System.out.println(e.getMessage());
}
}
}
im trying to write a class where it would take a text file,reverse its contents and write it back. The way i want to do it is to write the lines in a String[] array,reverse the lines and then write the text back to the text file. Problem is, when I start writing to the String array, it writes off only nulls and i know the text file is not empty. Im using a copy of the BufferedReader to read the lines. I can't seem to understand where am i wrong. When I initialize the String array textFile like down in the code, i have no problems reversing, but when i use the
String[] textFile = new String[getNumberOfLines ()];
method, it doesnt work.
public void reverse() throws IOException {
BufferedReader reader = new BufferedReader(new FileReader(WORK_FOLDER_LOCATION + FILE_NAME));
String[] textFile = new String[3];
try {
for (int i = 0; i < textFile.length; i++) {
textFile[i] = reader.readLine();
textFile[i] = reverseLine(textFile[i]);
}
} catch (IOException e) {
throw new IOException("There was a problem while operating with the reader.");
} finally {
reader.close();
}
writeReverseText(textFile);
}
private int getNumberOfLines(BufferedReader reader) throws IOException {
BufferedReader linesReader = reader;
int counter = 0;
try {
while (linesReader.readLine() != null) {
counter++;
}
linesReader.close();
} catch (IOException e) {
throw new IOException("There was a problem while counting the lines");
}
return counter;
}
private String reverseLine(String string) {
StringBuilder reversedString = new StringBuilder(string).reverse();
System.out.println(reversedString);
return reversedString.toString();
}
private void writeReverseText(String[] textFile) throws IOException {
BufferedWriter writer = new BufferedWriter(new FileWriter(WORK_FOLDER_LOCATION + FILE_NAME));
for (int i = 0; i < textFile.length; i++) {
writer.append(textFile[i]);
writer.append(System.lineSeparator());
}
writer.close();
}
EDIT I managed to solve the issue but changing the getNumberOfLines() method:
private int getNumberOfLines() throws IOException {
BufferedReader linesReader = new BufferedReader(new FileReader(WORK_FOLDER_LOCATION + FILE_NAME));
Hope this helps to the others, i would love to know why the previous code didn't work.
Your getNumberOfLines() method will read all the data from the BufferedReader - so unless you start reading the file again, there's nothing to read, and the very first call to readLine() will return null.
However, instead of doing this, you'd be better off just reading the file once, and populating a List<String>. For example:
List<String> lines = new ArrayList<>();
String line;
while ((line = reader.readLine()) != null) {
lines.add(reverseLine(line));
}
For a Java homework assignment, I need to create a class that reads and writes CSV files. I'm currently having some problems reading the the CSV. The code below, only outputs the first line of the code and then generates the following error message: 'Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1 at com.gc01.FileManager.CSVManager.main(CSVManager.java:27)".
I have looked at various examples, and I am aware of the 'opencsv' package, but I need to write this code myself. I have located the problem to the statement "System.out.print(data[i]);". However, when cross-referencing this code it all seems to be fine.
I am using the methods from the FileInput class, as specified by my teacher (http://www.devjavasoft.org/SecondEdition/SourceCode/Share/FileInput.java).
public class CSVManager {
public static void main(String [] args){
Scanner sc = new Scanner (System.in);
System.out.println("Please enter the file directory of the chosen CSV");
System.out.println("For Example: /Users/UserName/Downloads/FileName.csv");
///Users/ReeceAkhtar/Desktop/GeoIPCountryWhois.csv
final String fileName = sc.nextLine();
System.out.println("How many columns?");
final int columns = sc.nextInt();
BufferedReader br = null;
String line = "";
String splitBy = " , ";
try {
br = new BufferedReader(new FileReader(fileName));
while((line = br.readLine()) != null) {
for (int i = 0; i < columns; i++) {
String[] data = line.split(splitBy);
System.out.print(data[i]);
}
}
} catch (FileNotFoundException e){
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (br != null) {
try {
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
System.out.println("File Read");
}
}
Exception is very clear
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1
means, you are trying to access 1st element in the array which doesn't exist
Since you are saying System.out.print(data[i]); is the line where the exception is occurring, then for the first line data must have populated with only single element
Debug the issue with IDE to find out why split method is resulting unexpected elements. I suspect usage of spaces around , is the cause in " , "
Try this one. If you take splitting out the for loop everything will be okay.
String[] data = line.split(splitBy);
while((line = br.readLine()) != null){
for (int i = 0; i < columns; i++){
System.out.print(data[i]);
}
}
while((line = br.readLine()) != null){
for (int i = 0; i < columns; i++){
String[] data = line.split(splitBy);
System.out.print(data[i]);
}
You are splitting one line multiple times inside the for loop without any reason.
You are using " , " for splitting (which might be the reason you are having ArrayIndexOfBound exception) Instead use ","; use trim() on data[i] to get rid of trailing/leading white space if you wish to.
After Splitting, put checking whither data.length is equal to columns for consistency.
We are now in the era of JDK 7 where we can use try-with-resource which close the declared resource inside try(){} context, allowing us to get rid of finally block
So your could should look like as follows:
try (BufferedReader br = new BufferedReader(new FileReader(fileName))){
while((line = br.readLine()) != null){
String[] data = line.split(splitBy);
if(data.length != columns)continue; // check for consistency,
//might throw an exception
for (int i = 0; i < columns; i++){
System.out.print(data[i].trim());
}
}catch(IoExection ex)
{
ex.printStackTrace();
}
I have a file that contain 100 line
each line contain one tag
I need to obtain the tag value given its rank which is the "id" of TagVertex Class
public abstract class Vertex <T>{
String vertexId ;// example Tag1
T vertexValue ;
public abstract T computeVertexValue();
}
public class TagVertex extends Vertex<String> {
#Override
public String computeVertexValue() {
// How to get the String from my file?
return null;
}
T try this but it doesnt work
public static void main(String args[]) {
File source //
int i=90;
int j=0;
String s = null;
try {
Scanner scanner = new Scanner(source);
while (scanner.hasNextLine()) {
if (j==i) s= scanner.nextLine();
else j++;
}
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println(s);
}}
Although there is a way to skip characters with BufferedReader, I don't think there's is a built-in way to skip whole lines.
BufferedReader bf = new BufferedReader(new FileReader("MyFile.txt"));
for(int i = 1; i < myVertex.vertexId; i++){
bf.readLine();
}
String n = bf.readLine();
if(n != null){
System.out.println(n);
}
I think there may be a better idea though.
This is command u can use to read from file:
BufferedReader bf = new BufferedReader(new FileReader("filename"));
This will read the file to the buffer.
Now, for reading each line u should use a while loop and read each line into string.
Like:
String str;
while((str = bf.readLine()) != null){
//handle each line untill the end of file which will be null and quit the loop
}
So this is what I have so far :
public String[] findStudentInfo(String studentNumber) {
Student student = new Student();
Scanner scanner = new Scanner("Student.txt");
// Find the line that contains student Id
// If not found keep on going through the file
// If it finds it stop
// Call parseStudentInfoFromLine get the number of courses
// Create an array (lines) of size of the number of courses plus one
// assign the line that the student Id was found to the first index value of the array
//assign each next line to the following index of the array up to the amount of classes - 1
// return string array
}
I know how to find if a file contains the string I am trying to find but I don't know how to retrieve the whole line that its in.
This is my first time posting so If I have done anything wrong please let me know.
You can do something like this:
File file = new File("Student.txt");
try {
Scanner scanner = new Scanner(file);
//now read the file line by line...
int lineNum = 0;
while (scanner.hasNextLine()) {
String line = scanner.nextLine();
lineNum++;
if(<some condition is met for the line>) {
System.out.println("ho hum, i found it on line " +lineNum);
}
}
} catch(FileNotFoundException e) {
//handle this
}
Using the Apache Commons IO API https://commons.apache.org/proper/commons-io/ I was able to establish this using FileUtils.readFileToString(file).contains(stringToFind)
The documentation for this function is at https://commons.apache.org/proper/commons-io/javadocs/api-2.4/org/apache/commons/io/FileUtils.html#readFileToString(java.io.File)
Here is a java 8 method to find a string in a text file:
for (String toFindUrl : urlsToTest) {
streamService(toFindUrl);
}
private void streamService(String item) {
try (Stream<String> stream = Files.lines(Paths.get(fileName))) {
stream.filter(lines -> lines.contains(item))
.forEach(System.out::println);
} catch (IOException e) {
e.printStackTrace();
}
}
When you are reading the file, have you considered reading it line by line? This would allow you to check if your line contains the file as your are reading, and you could then perform whatever logic you needed based on that?
Scanner scanner = new Scanner("Student.txt");
String currentLine;
while((currentLine = scanner.readLine()) != null)
{
if(currentLine.indexOf("Your String"))
{
//Perform logic
}
}
You could use a variable to hold the line number, or you could also have a boolean indicating if you have passed the line that contains your string:
Scanner scanner = new Scanner("Student.txt");
String currentLine;
int lineNumber = 0;
Boolean passedLine = false;
while((currentLine = scanner.readLine()) != null)
{
if(currentLine.indexOf("Your String"))
{
//Do task
passedLine = true;
}
if(passedLine)
{
//Do other task after passing the line.
}
lineNumber++;
}
This will find "Mark Sagal" in Student.txt. Assuming Student.txt contains
Student.txt
Amir Amiri
Mark Sagal
Juan Delacruz
Main.java
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.ArrayList;
public class Main {
public static void main(String[] args) {
final String file = "Student.txt";
String line = null;
ArrayList<String> fileContents = new ArrayList<>();
try {
FileReader fReader = new FileReader(file);
BufferedReader fileBuff = new BufferedReader(fReader);
while ((line = fileBuff.readLine()) != null) {
fileContents.add(line);
}
fileBuff.close();
} catch (Exception e) {
System.out.println(e.getMessage());
}
System.out.println(fileContents.contains("Mark Sagal"));
}
}
I am doing something similar but in C++. What you need to do is read the lines in one at a time and parse them (go over the words one by one). I have an outter loop that goes over all the lines and inside that is another loop that goes over all the words. Once the word you need is found, just exit the loop and return a counter or whatever you want.
This is my code. It basically parses out all the words and adds them to the "index". The line that word was in is then added to a vector and used to reference the line (contains the name of the file, the entire line and the line number) from the indexed words.
ifstream txtFile;
txtFile.open(path, ifstream::in);
char line[200];
//if path is valid AND is not already in the list then add it
if(txtFile.is_open() && (find(textFilePaths.begin(), textFilePaths.end(), path) == textFilePaths.end())) //the path is valid
{
//Add the path to the list of file paths
textFilePaths.push_back(path);
int lineNumber = 1;
while(!txtFile.eof())
{
txtFile.getline(line, 200);
Line * ln = new Line(line, path, lineNumber);
lineNumber++;
myList.push_back(ln);
vector<string> words = lineParser(ln);
for(unsigned int i = 0; i < words.size(); i++)
{
index->addWord(words[i], ln);
}
}
result = true;
}
Here is the code of TextScanner
public class TextScanner {
private static void readFile(String fileName) {
try {
File file = new File("/opt/pol/data22/ds_data118/0001/0025090290/2014/12/12/0029057983.ds");
Scanner scanner = new Scanner(file);
while (scanner.hasNext()) {
System.out.println(scanner.next());
}
scanner.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
if (args.length != 1) {
System.err.println("usage: java TextScanner1"
+ "file location");
System.exit(0);
}
readFile(args[0]);
}
}
It will print text with delimeters