I am trying to display the contents of multiple rows in a text file. I can do it no problem with a single line, but I add another line and I'm not sure what I need to add to my code to make it move on to the next line. I need myValues[1] to be the same as myValues[n] only to be the second line in the file. I believe I need to se a new String as the next line but I'm not sure exactly how with this setup.
package a3;
import java.io.*;
public class A3
{
public static void main(String [] args)
{
String animals = "animals.txt";
String line = null;
try
{
FileReader fileReader = new FileReader(animals);
BufferedReader bufferedReader = new BufferedReader(fileReader);
String aLine = bufferedReader.readLine();
String myValues[] = aLine.split(" ");
int n = 0;
while((line = bufferedReader.readLine()) != null)
{
System.out.println(myValues[n] + " " + myValues[1]);
n++;
}
bufferedReader.close();
}
catch(FileNotFoundException ex)
{
System.out.println("Unable to open file '" + animals + "'");
}
catch(IOException ex)
{
System.out.println("Error reading file '" + animals + "'");
}
}
}
Here is another simple way to read lines from a file and do the processing:
There is a java.io.LineNumberReader class which helps do it.
Sample snippet:
LineNumberReader lnr = new LineNumberReader(new FileReader(new File(filename)));
String line = null;
while ((line = lnr.readLine()) != null)
{
// Do you processing on line
}
In your code, the array myValues is never changed and always contains the values for the first line of text. You need to change it each time you get a new line, this is done in your while loop :
[...]
while((line = bufferedReader.readLine()) != null)
{
myValues[] = line.split(" ");
System.out.println(myValues[n] + " " + myValues[1]);
n++;
}
Obviously not tested...
You could also read all lines to a String list like this:
import java.io.File;
import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.util.List;
List<String> lines = Files.readAllLines(new File(animals).toPath(), Charset.defaultCharset());
And than iterate over the line list, split the values and output them.
Related
I would like to store only the first column that is contained in the .txt file.
hello28 23232
hello27 23232
hello25 12321
This is the code I have so far, however at the moment it stores every line in the file; how can I make it so that only the first column is stored (The one which contains the user names of the users)?
public static boolean checkUserExists(String userName){
String line = "";
ArrayList <String> userNames = new ArrayList <String>();
try{
FileReader fr = new FileReader("investments.txt");
BufferedReader br = new BufferedReader(fr);
while((line = br.readLine()) != null) {
userNames.add(line);
}
}
catch(IOException e){
System.out.println("File not found!");
}
if (userNames.contains(userName)){
return false;
}
else{
return true;
}
}
All you need to do is just to split each line using whitespace as a delimiter and keep the first token, and repeat that for every line:
This can be achieved using the following line of code which uses the split function (see more info here http://docs.oracle.com/javase/7/docs/api/java/lang/String.html#split(java.lang.String))
line.split("\\s+");
Then, the zero-th (0) element contains the first column, as you wish to do
There you go a fully working class:
import java.io.IOException;
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.ArrayList;
class white {
public static void main(String[] args) {
String line = "";
String username = "";
ArrayList <String> userNames = new ArrayList <String>();
try{
FileReader fr = new FileReader("investments.txt");
BufferedReader br = new BufferedReader(fr);
while((line = br.readLine()) != null) {
line.split("\\s+");
userNames.add(line.split("\\s+")[0]);
System.out.println(line.split("\\s+")[0]);
}
}
catch(IOException e){
System.out.println("File not found!");
}
}
}
OUTPUT:
hello28
hello27
hello25
You can extract the part of the line preceding the first space:
userNames.add(line.substring(0, line.indexOf(' ') ));
Below is what the text document looks like. The first line is the number of elements that I want the array to contain. The second is the ID for the product, separated by # and the third line is the total price of the products once again separated by #
10
PA/1234#PV/5732#Au/9271#DT/9489#HY/7195#ZR/7413#bT/4674#LR/4992#Xk/8536#kD/9767#
153#25#172#95#235#159#725#629#112#559#
I want to use the following method to pass inputFile to the readProductDataFile method:
public static Product[] readProductDataFile(File inputFile){
// Code here
}
I want to create an array of size 10, or maybe an arrayList. Preferably to be a concatenation of Customer ID and the price, such as Array[1] = PA/1234_153
There you go the full class, does exactly what you want:
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.Arrays;
import java.io.FileNotFoundException;
import java.io.IOException;
class myRead{
public static void main(String[] args) throws FileNotFoundException, IOException {
BufferedReader inputFile = new BufferedReader(new FileReader("test.txt"));
String numberOfElements = inputFile.readLine();
//this is the first line which contains the number "10"
//System.out.println(numberOfElements);
String secondLine = inputFile.readLine();
//this is the second line which contains your data, split it using "#" as a delimiter
String[] strArray = secondLine.split("#");
//System.out.println(Arrays.toString(strArray));
//System.out.println(strArray[0]);
String thirdLine = inputFile.readLine();
//this is the third line which contains your data, split it using "#" as a delimiter
String[] dataArray = thirdLine.split("#");
//combine arrays
String[] combinedArray = new String[strArray.length];
for (int i=0;i<strArray.length;i++) {
combinedArray[i]=strArray[i]+"_"+dataArray[i];
System.out.println(combinedArray[i]);
}
}
}
OUTPUT:
PA/1234_153
PV/5732_25
Au/9271_172
DT/9489_95
HY/7195_235
ZR/7413_159
bT/4674_725
LR/4992_629
Xk/8536_112
kD/9767_559
The trick in what I am doing is using a BufferedReader to read the file, readLine to read each of the three lines, split("#"); to split each token using the # as the delimiter and create the arrays, and combinedArray[i]=strArray[i]+"_"+dataArray[i]; to put the elements in a combined array as you want...!
public static Product[] readProductDataFile(File inputFile){
BufferedReader inputFile = new BufferedReader(new FileReader(inputFile));
// the rest of my previous code goes here
EDIT: Everything together with calling a separate method from inside the main, with the file as an input argument!
import java.io.BufferedReader;
import java.io.FileReader;
import java.util.Arrays;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.File;
class myRead{
public static void main(String[] args) throws FileNotFoundException, IOException {
File myFile = new File("test.txt");
readProductDataFile(myFile);
}
public static String[] readProductDataFile(File inputFile) throws FileNotFoundException, IOException{
BufferedReader myReader = new BufferedReader(new FileReader("test.txt"));
String numberOfElements = myReader.readLine();
//this is the first line which contains the number "10"
//System.out.println(numberOfElements);
String secondLine = myReader.readLine();
//this is the second line which contains your data, split it using "#" as a delimiter
String[] strArray = secondLine.split("#");
//System.out.println(Arrays.toString(strArray));
//System.out.println(strArray[0]);
String thirdLine = myReader.readLine();
//this is the third line which contains your data, split it using "#" as a delimiter
String[] dataArray = thirdLine.split("#");
//combine arrays
String[] combinedArray = new String[strArray.length];
for (int i=0;i<strArray.length;i++) {
combinedArray[i]=strArray[i]+"_"+dataArray[i];
System.out.println(combinedArray[i]);
}
return combinedArray;
}
}
OUTPUT
PA/1234_153
PV/5732_25
Au/9271_172
DT/9489_95
HY/7195_235
ZR/7413_159
bT/4674_725
LR/4992_629
Xk/8536_112
kD/9767_559
You don't even need the first line. Just read the second line directly into a single string and then split it by using String,split() method.
Read more for split method here.
You could use something like this (Be aware that i can't test it at the moment)
BufferedReader in = null;
try {
in = new BufferedReader(new FileReader("fileeditor.txt"));
String read = null;
String firstLine=in.readLine();
//reads the first line
while ((read = in.readLine()) != null) {
// reads all the other lines
read = in.readLine();
String[] splited = read.split("#");
//split the readed row with the "#" character
for (String part : splited) {
System.out.println(part);
}
}
} catch (IOException e) {
System.out.println("There was a problem: " + e);
e.printStackTrace();
} finally {
try {
//close file
in.close();
} catch (Exception e) {
}
}
This is how you can do it using Java (don't forget to import):
public static Product[] readProductDataFile(File inputFile){
Scanner s = new Scanner(inputFile);
String data = "";
while(s.hasNext())
data += s.nextLine();
String[] dataArray = data.split("#");
}
You can try this way ..
Reading line by line and storing each row in a array.
Use while storing so it will split and save .
String[] strArray = secondLine.split("#");
Now use the for loop and concat the values as u wish and save ina third array .
For(int i=0 ;i< file.readline;i++)
{
string s = a[customerid];
s.concat(a[productid]);
a[k] =s;
}
I've got a text file called log.txt.
It's got the following data
1,,Mon May 05 00:05:45 WST 2014,textFiles/a.txt,images/download.jpg
2,,Mon May 05 00:05:45 WST 2014,textFiles/a.txt,images/download.jpg
The numbers before the first comma are indexes that specify each item.
What I want to do is to read the file and then replace one part of the string(e.g. textFiles/a.txt) in a given line with another value(e.g. something/bob.txt).
This is what I have so far:
File log= new File("log.txt");
String search = "1,,Mon May 05 00:05:45 WST 2014,textFiles/a.txt,images/download.jpg;
//file reading
FileReader fr = new FileReader(log);
String s;
try (BufferedReader br = new BufferedReader(fr)) {
while ((s = br.readLine()) != null) {
if (s.equals(search)) {
//not sure what to do here
}
}
}
You could create a string of total file content and replace all the occurrence in the string and write to that file again.
You could something like this:
File log= new File("log.txt");
String search = "textFiles/a.txt";
String replace = "replaceText/b.txt";
try{
FileReader fr = new FileReader(log);
String s;
String totalStr = "";
try (BufferedReader br = new BufferedReader(fr)) {
while ((s = br.readLine()) != null) {
totalStr += s;
}
totalStr = totalStr.replaceAll(search, replace);
FileWriter fw = new FileWriter(log);
fw.write(totalStr);
fw.close();
}
}catch(Exception e){
e.printStackTrace();
}
One approach would be to use String.replaceAll():
File log= new File("log.txt");
String search = "textFiles/a\\.txt"; // <- changed to work with String.replaceAll()
String replacement = "something/bob.txt";
//file reading
FileReader fr = new FileReader(log);
String s;
try {
BufferedReader br = new BufferedReader(fr);
while ((s = br.readLine()) != null) {
s.replaceAll(search, replacement);
// do something with the resulting line
}
}
You could also use regular expressions, or String.indexOf() to find where in a line your search string appears.
Solution with Java Files and Stream
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
private static void replaceAll(String filePath, String text, String replacement) {
Path path = Paths.get(filePath);
// Get all the lines
try (Stream<String> stream = Files.lines(file, StandardCharsets.UTF_8)) {
// Do the replace operation
List<String> list = stream.map(line -> line.replace(text, replacement)).collect(Collectors.toList());
// Write the content back
Files.write(file, list, StandardCharsets.UTF_8);
} catch (IOException e) {
LOG.error("IOException for : " + file, e);
e.printStackTrace();
}
}
Usage
replaceAll("test.txt", "original text", "new text");
A very simple solution would be to use:
s = s.replace( "textFiles/a.txt", "something/bob.txt" );
To replace all occurrences, use replaceAll shown in another proposal, where a regular expression is used - take care to escape all magic characters, as indicated there.
I want to read a text file containing space sepearted values. Values are integers. How can I read it? I want to read each line and after go to next.
The contents are as the example:
"12/11/2012" "00.00.01" 0,100
"12/11/2012" "00.00.05" 0,140
"12/11/2012" "00.00.09" 0,240
"12/11/2012" "00.00.13" 0,247
The first column is the date, the second is second and the third is litres.
How can I do it with a Java program?
I think of using Scanner class. I made this program:
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class ScannerExample {
public static void main(String args[]) throws FileNotFoundException {
File text = new File("C:\Users\Desktop\test\test.txt");
Scanner scnr = new Scanner(text);
int lineNumber = 1;
while(scnr.hasNextLine()){
String line = scnr.nextLine();
System.out.println("line " + lineNumber + " :" + line);
lineNumber++;
}
}
}
But I haven't the result that I would like to have.
Any help?
The easiest in Java is to use Apache Commons Libraries.
Just add the following dependency in your pom file (if you are using maven)
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-io</artifactId>
<version>1.3.2</version>
</dependency>
Then you can do
File file = new File("yourFile.txt");
List<String> lines = FileUtils.readLines(file);
You will get each of line of your file in the list. Then to get the content of your file:
for(String line : lines){
String[] columns = line.split(" ") //because your columns seem to be separated by a white space
}
The array columns will contain your data
DateFormat format = new SimpleDateFormat("dd/mm/yyyy");
//column 1
Date date = format.format(column[0]);
//column 2
//I'm not sure to get your second column, is it just second or can it be more?
//column 3
double litres = Double.parseDouble(column[2]);
This looks like a CSV file. You could use a CSV tool to read it.
I know CSV means 'comma separated values', and your file doesn't have commas, but CSV tools can also read files separated by space.
This would be done by simple google search as well.. first you would find code like this:
import java.io.*;
class FileRead
{
public static void main(String args[])
{
try{
// Open the file that is the first
// command line parameter
FileInputStream fstream = new FileInputStream("textfile.txt");
// Use DataInputStream to read binary NOT text.
BufferedReader br = new BufferedReader(new InputStreamReader(fstream));
String strLine;
//Read File Line By Line
while ((strLine = br.readLine()) != null) {
// Print the content on the console
System.out.println (strLine);
}
//Close the input stream
in.close();
}catch (Exception e){//Catch exception if any
System.err.println("Error: " + e.getMessage());
}
}
}
Replace the System.out.println with some code to get all content from " to " Like:
while ((strLine = br.readLine()) != null) {
int start = 1, pos = 0,lastpos= 1;
String dates, times, values;
if(strLine.indexOf("\"",lastpos) > 0){
pos = strLine.indexOf("\"",lastpos);
dates = strLine.substring(start,pos);
lastpos = pos+3;//replace through search for \"
pos = strLine.indexOf("\"",lastpos);
times = strLine.substring(lastpos,pos);
lastpos = pos+2;//replace through search for \"
values = strLine.substring(lastpos,strLine.length());
System.out.println(dates);//Convert to Date
System.out.println(times);//Convert to time
System.out.println(values);//Convert to Integer.valueOf/)
System.out.println("next line");
}
}
I am implementing a RPN calculator in Java and need help creating a class to parse the equations into separate tokens.
My input file will have an unknown number of equations similar to the ones shown below:
49+62*61-36
4/64
(53+26)
0*72
21-85+75-85
90*76-50+67
46*89-15
34/83-38
20/76/14+92-15
I have already implemented my own generic stack class to be used in the program, but I am now trying to figure out how to read data from the input file. Any help appreciated.
I've posted the source code for my stack class at PasteBin, in case it may help.
I have also uploaded the Calculator with no filereading to PasteBin to show what I have done already.
I have now managed to get the file read in and the tokens broken up thanks for the help. I am getting an error when it reaches the end of the file and was wondering how to solve that?
Here is the code:
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.util.StringTokenizer;
public class TestClass {
static public void main(String[] args) throws IOException {
File file = new File("testEquations.txt");
String[] lines = new String[10];
try {
FileReader reader = new FileReader(file);
BufferedReader buffReader = new BufferedReader(reader);
int x = 0;
String s;
while((s = buffReader.readLine()) != null){
lines[x] = s;
x++;
}
}
catch(IOException e){
System.exit(0);
}
String OPERATORS = "+-*/()";
for (String st : lines) {
StringTokenizer tokens = new StringTokenizer(st, OPERATORS, true);
while (tokens.hasMoreTokens()) {
String token = tokens.nextToken();
if (OPERATORS.contains(token))
handleOperator(token);
else
handleNumber(token);
}
}
}
private static void handleNumber(String token) {
System.out.println(""+token);
}
private static void handleOperator(String token) {
System.out.println(""+token);
}
}
Also How would I make sure the RPN works line by line? I am getting quite confused by the algorithms I am trying to follow.
Because all of the operators are single characters, you can instruct StringTokenizer to return them along with the numeric tokens.
String OPERATORS = "+-*/()";
String[] lines = ...
for (String line : lines) {
StringTokenizer tokens = new StringTokenizer(line, OPERATORS, true);
while (tokens.hasMoreTOkens()) {
String token = tokens.nextToken();
if (OPERATORS.contains(token))
handleOperator(token);
else
handleNumber(token);
}
}
As your question has now changed completely from it's original version - this is in response to your original one, which was how to use FileReader to get the values from your file.
This will put each line into a separate element of a String array. You should probably use an ArrayList instead, as it's far more flexible, but I have just done this as a quick demo - you can clean it up as you wish, although I notice the code you are using expects a String array as it's input. Perhaps you could read the values initially into an ArrayList, then copy that to an array once you have all the lines - that way you can put as many lines in as you wish and keep your code flexible for changes in the number of lines in your input file.
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
public class TestClass {
static public void main(String[] args) {
File file = new File("myfile.txt");
String[] lines = new String[10];
try {
FileReader reader = new FileReader(file);
BufferedReader buffReader = new BufferedReader(reader);
int x = 0;
String s;
while((s = buffReader.readLine()) != null){
lines[x] = s;
x++;
}
}
catch(IOException e){
//handle exception
}
// And just to prove we have the lines right where we want them..
for(String st: lines)
System.out.println(st);
}
}
You mentioned before that you were using the code on this link:
http://www.technical-recipes.com/2011/a-mathematical-expression-parser-in-java/#more-1658
This appears to already deal with operator precedence doesn't it? And with parsing each String from the array and sorting them into numbers or operators? From my quick look it at least it appears to do that.
So it looks like all you need is for your lines to be in a String array, which you then pass to the code you already have. From what I can see anyway.
Obviously this doesn't address the issue of numbers greater than 9, but hopefully it helps with the first half.
:-)
public void actionPerformed(ActionEvent e) {
double sum=0;
int count = 0 ;
try {
String nomFichier = "Fichier.txt";
FileReader fr = new FileReader(nomFichier);
BufferedReader br = new BufferedReader(fr);
String ligneLue;
do {
ligneLue = br.readLine();
if(ligneLue != null) {
StringTokenizer st = new StringTokenizer(ligneLue, ";");
String nom = st.nextToken();
String prenom = st.nextToken();
String age = st.nextToken();
String tele = st.nextToken();
String adress = st.nextToken();
String codePostal = st.nextToken();
String ville = st.nextToken();
String paye = st.nextToken();
double note = Double.parseDouble(st.nextToken());
count++;
}
}
while(ligneLue != null);
br.close();
double mediane = count / 2;
if(mediane % 2 == 0) {
JOptionPane.showMessageDialog(null, "Le mediane dans le fichier est " + mediane);
}
else {
mediane +=1;
JOptionPane.showMessageDialog(null, "Le mediane dans le fichier est " + mediane);
}
}//fin try
catch(FileNotFoundException ex) {
System.out.println(ex.getMessage());
}
catch(IOException ex) {
System.out.println(ex.getMessage());
}
}