Develop Reference

Java Extracting values from text files

I have many text files (up to 20) and each file has it's contents like this
21.0|11|1/1/1997
13.3|12|2/1/1997
14.6|9|3/1/1997
and every file has approximately more than 300 lines.
so the problem I'm facing is this, how can I extract all and only the first values
of the file's content.
for example I want to extract the values (21.0,13.3,14.6.....etc) so I can decide the max number and minimum in all of the 20 files.
I have wrote this code from my understanding to experience it on of the files
but it didn't work
String inputFileName = "Date.txt";
File inputFile = new File(inputFileName);
Scanner input = new Scanner(inputFile);
int count = 0;
while (input.hasNext()){
double line = input.nextDouble(); //Error occurs "Exception in thread "main" java.util.InputMismatchException"
count++;
double [] lineArray= new double [365];
lineArray[count]= line;
System.out.println(count);
for (double s : lineArray){
System.out.println(s);
System.out.println(count);
and this one too
String inputFileName = "Date.txt";
File inputFile = new File(inputFileName);
Scanner input = new Scanner(inputFile);
while (input.hasNext()){
String line = input.nextLine();
String [] lineArray = line.split("//|");
for (String s : lineArray){
System.out.println(s+" ");
}
Note: I'm still kind of a beginner in Java
I hope I was clear and thanks

For each line of text, check whether it contains the pipe character. If it does, grab the first portion of the text and parse it to double.
double val = 0.0;
Scanner fScn = new Scanner(new File(“date.txt”));
while(fScn.hasNextLine()){ //Can also use a BufferedReader
data = fScn.nextLine();
if(data.contains("|")) //Ensure line contains "|"
val = Double.parseDouble(data.substring(0, data.indexOf("|"))); //grab value
}

Or you could try some streams, cool stuff
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
public class MinMaxPrinter {
public static void main(String[] args) {
final List<String> files = Arrays.asList("file", "names", "that", "you", "need");
new MinMaxPrinter().printMinMax(files);
}
public void printMinMax(List<String> fileNames) {
List<Double> numbers = fileNames.stream()
.map(Paths::get)
.flatMap(this::toLines)
.map(line -> line.split("\\|")[0])
.map(Double::parseDouble)
.collect(Collectors.toList());
double max = numbers.stream().max(Double::compare).get();
double min = numbers.stream().min(Double::compare).get();
System.out.println("Min: " + min + " Max: " + max);
}
private Stream<String> toLines(Path path) {
try {
return Files.lines(path);
} catch (IOException e) {
return Stream.empty();
}
}
}

try (BufferedReader br = new BufferedReader(new FileReader(file))) {
String line;
while ((line = br.readLine()) != null) {
String res = s.split("\\|")[0];
}
}

Buffered Reader read certain line and text

This is my first post, so i'm not sure how things work here.
Basically, i need some help/advice with my code. The method need to read a certain line and print out the text after the inputted text and =
The text file would like
A = Ant
B = Bird
C = Cat
So if the user it input "A" it should print out something like
-Ant
So far, i manage to make it ignore "=" but still print out the whole file
here is my code:
public static void readFromFile() {
System.out.println("Type in your word");
Scanner scanner = new Scanner(System.in);
String input = scanner.next();
String output = "";
try {
FileReader fr = new FileReader("dictionary.txt");
BufferedReader br = new BufferedReader(fr);
String[] fields;
String temp;
while((input = br.readLine()) != null) {
temp = input.trim();
if (temp.startsWith(input)) {
String[] splitted = temp.split("=");
output += splitted[1] + "\n";
}
}
System.out.print("-"+output);
}
catch(IOException e) {
}
}

It looks like this line is the problem, as it will always be true.
if (temp.startsWith(input))
You need to have a different variables for the lines being read out of the file and for the input you're holding from the user. Try something like:
String fileLine;
while((fileLine = br.readLine()) != null)
{
temp = fileLine.trim();
if (temp.startsWith(input))
{
String[] splitted = temp.split("=");
output += splitted[1] + "\n";
}
}

You can use useDelimiter() method of Scanner to split input text
scanner.useDelimiter("(.)*="); // Matches 0 or more characters followed by '=', and then gives you what is after `=`
The following code is something I've tried in IDEONE (http://ideone.com/TBwCFj)
Scanner s = new Scanner(System.in);
s.useDelimiter("(.)*=");
while(s.hasNext())
{
String ss = s.next();
System.out.print(ss);
}
/**
* Output
*
*/
Ant
Bat

You need to first split the text file by new line "\n" (assuming after each "A = Ant", "B = Bird" ,"C = Cat" declaration it starts with a new line) and THEN locate the inputted character and further split that by "=" as you were doing.
So you will need two arrays of Strings (String[ ]) one for each line and one for the separation of each line into e.g. "A" and "Ant".
You are very close.

try this, it works: STEPS:
1) read input using scanner
2) read file using bufferedreader
3) split each line using "-" as a delimiter
4) compare first character of line with input
5) if first character is equal to input then print the associated value, preceded by a "-"
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.File;
import java.util.Scanner;
class myRead{
public static void main(String[] args) throws FileNotFoundException, IOException {
System.out.println("Type in your word");
Scanner scanner = new Scanner(System.in);
String input = scanner.next();
long numberOfLines = 0;
BufferedReader myReader = new BufferedReader(new FileReader("test.txt"));
String line = myReader.readLine();
while(line != null){
String[] parts = line.split("=");
if (parts[0].trim().equals(input.trim())) {
System.out.println("-"+parts[1]);
}
line = myReader.readLine();
}
}
}
OUTPUT (DEPENDING ON INPUT):
- Ant
- Bird
- Cat

Input a text file in a two dimensional array with doubles

I'm new in Java.
I want to input a text file and create from it a two dimensional array the input is
like this
12,242 323,2324
23,4434 23,4534
23,434 56,3434
....
34,434 43,3443
I have tried
import java.util.Scanner;
import java.io.File;
import java.io.IOException;
public class InputText {
/**
* #param args the command line arguments
* #throws java.io.IOException
*/
public static void main(String[] args) throws IOException {
int i=0;
File file;
file = new File("file.txt");
Scanner read=new Scanner(file);
while (read.hasNextLine()) {
String line=read.nextLine();
System.out.println(line);
}
}
}
which gives me the input but I cannot insert this in an array I tried different ways like splitting it.
Any suggestions?
Sorry for not being clear. The input i mentioned is doubles seperated by spaces. Also the format i gave you is what i get after i run the part of the programm i wrote. What i see in the text file is the numbers seperated by spaces. I tried to implement your suggestion but nothing seemed to work. I'm really lost here....

If you want to split a line to two numbers you can use
string[] numbers = line.split("\\s+");
If you want to read a double with comma
NumberFormat format = NumberFormat.getInstance(Locale.FRANCE);
...
double d1 = format.parse(numbers[0]).doubleValue();
double d2 = format.parse(numbers[1]).doubleValue();
Personally i prefer to use scanner. In that case create it with
Scanner scanner = new Scanner(file);
while (scanner.hasNextLine()) {
Scanner scanner2 = new Scanner(scanner.nextLine()).useLocale(Locale.FRANCE);
if (!scanner2.hasNextDouble()){
System.out.println("Do not have a pair");
continue;
}
double d1 = scanner2.nextDouble();
if (!scanner2.hasNextDouble()){
System.out.println("Do not have a pair");
continue;
}
double d2 = scanner2.nextDouble();
//do something
}

After reading the line.. you will have to again split the string on ','. The split string need to be converted into interger. YOu can see as below:
import java.util.Scanner;
import java.io.File;
import java.io.IOException;
public class InputText {
/**
* #param args the command line arguments
* #throws java.io.IOException
*/
public static void main(String[] args) throws IOException {
int i = 0;
File file;
file = new File("file.txt");
Scanner read = new Scanner(file);
while (read.hasNextLine()) {
String line = read.nextLine();
String[] numbers = line.split(",");
for (i = 0; i < numbers.lenght; i++) {
String numStr = numbers[i];
String x=numStr.replaceAll("\\s+",""); //eleminate the space in any.
Double num = Double.valueOf(x);
System.out.println(" num is: " + num); //Here you can store the number in array.
}
}
}
}

Try to use something like that(add also try catch statement)
String line = "";
br = new BufferedReader(new FileReader("file.txt"));
int i=0;
while ((line = br.readLine()) != null) {
// use comma as separator
String[] lineArray= line.split(",");
for(int j=0;j<lineArray.length;j++){
my2DArray[i][j] = lineArray[j];
}
i++;
}
for(int i=0;i<my2DArray[0].length;i++){
for(int j=0;j<my2DArray[1].length;j++){
System.out.print(my2DArray[i][j] + " ");
}
}

Reading a file in Java

I have the following code to open and read a file. I'm having trouble figuring out how I can have it go through and print the total number of each character in the file, print the first and last character, and print the character exactly in the middle of the file. What's the most efficient way to do this?
This is the main class:
import java.io.IOException;
public class fileData {
public static void main(String[ ] args) throws IOException {
String file_name = "/Users/JDB/NetBeansProjects/Program/src/1200.dna";
try {
ReadFile file = new ReadFile(file_name);
String[] arrayLines = file.OpenFile();
int i;
for (i=0; i<arrayLines.length; i++)
{
System.out.println(arrayLines[i]);
}
}
catch (IOException e) {
System.out.println(e.getMessage()) ;
}
}
}
and the other class:
import java.io.IOException;
import java.io.FileReader;
import java.io.BufferedReader;
public class ReadFile {
private String path;
public ReadFile (String file_path)
{
path = file_path;
}
public String[] OpenFile() throws IOException
{
FileReader fr = new FileReader(path);
BufferedReader textReader = new BufferedReader(fr);
int numberOfLines = readLines();
String[] textData = new String[numberOfLines];
int i;
for(i=0; i<numberOfLines; i++)
{
textData[i] = textReader.readLine();
}
textReader.close();
return textData;
}
int readLines() throws IOException
{
FileReader file_to_read = new FileReader(path);
BufferedReader bf = new BufferedReader(file_to_read);
String aLine;
int numberOfLines = 0;
while (( aLine = bf.readLine() ) != null)
{
numberOfLines++;
}
bf.close();
return numberOfLines;
}

Some hints which might help.
A Map can be used to store information about each character in the alphabet.
The middle of the file can be found from the size of the file.

These few lines of code will do it (using Apache's FileUtils library):
import org.apache.commons.io.FileUtils;
public static void main(String[] args) throws IOException {
String str = FileUtils.readFileToString(new File("myfile.txt"));
System.out.println("First: " + str.charAt(0));
System.out.println("Last: " + str.charAt(str.length() - 1));
System.out.println("Middle: " + str.charAt(str.length() / 2));
}
Anyone who says "you can't use libraries for homework" isn't being fair - in the real world we always use libraries in preference to reinventing the wheel.

The easiest way to understand I can think of is to read the entire file in as a String. Then use the methods on the String class to get the first, last, and middle character (character at index str.length()/2).
Since you are already reading in the file a line at a time, you can use a StringBuilder to construct a string out of those lines. Using the resulting String, the charAt() and substring() methods you should be able to get out everything you want.

Java file read problem

I have a java problem. I am trying to read a txt file which has a variable number of integers per line, and for each line I need to sum every second integer! I am using scanner to read integers, but can't work out when a line is done. Can anyone help pls?

have a look at the BufferedReader class for reading a textfile and at the StringTokenizer class for splitting each line into strings.
String input;
BufferedReader br = new BufferedReader(new FileReader("foo.txt"));
while ((input = br.readLine()) != null) {
input = input.trim();
StringTokenizer str = new StringTokenizer(input);
String text = str.nextToken(); //get your integers from this string
}

If I were you, I'd probably use FileUtils class from Apache Commons IO. The method readLines(File file) returns a List of Strings, one for each line. Then you can simply handle one line at a time.
Something like this:
File file = new File("test.txt");
List<String> lines = FileUtils.readLines(file);
for (String line : lines) {
// handle one line
}
(Unfortunately Commons IO doesn't support generics, so the there would be an unchecked assignment warning when assigning to List<String>. To remedy that use either #SuppressWarnings, or just an untyped List and casting to Strings.)
This is, perhaps, an example of a situation where one can apply "know and use the libraries" and skip writing some lower-level boilerplate code altogether.

or scrape from commons the essentials to both learn good technique and skip the jar:
import java.io.*;
import java.util.*;
class Test
{
public static void main(final String[] args)
{
File file = new File("Test.java");
BufferedReader buffreader = null;
String line = "";
ArrayList<String> list = new ArrayList<String>();
try
{
buffreader = new BufferedReader( new FileReader(file) );
line = buffreader.readLine();
while (line != null)
{
line = buffreader.readLine();
//do something with line or:
list.add(line);
}
} catch (IOException ioe)
{
// ignore
} finally
{
try
{
if (buffreader != null)
{
buffreader.close();
}
} catch (IOException ioe)
{
// ignore
}
}
//do something with list
for (String text : list)
{
// handle one line
System.out.println(text);
}
}
}

This is the solution that I would use.
import java.util.ArrayList;
import java.util.Scanner;
public class Solution1 {
public static void main(String[] args) throws IOException{
String nameFile;
File file;
Scanner keyboard = new Scanner(System.in);
int total = 0;
System.out.println("What is the name of the file");
nameFile = keyboard.nextLine();
file = new File(nameFile);
if(!file.exists()){
System.out.println("File does not exit");
System.exit(0);
}
Scanner reader = new Scanner(file);
while(reader.hasNext()){
String fileData = reader.nextLine();
for(int i = 0; i < fileData.length(); i++){
if(Character.isDigit(fileData.charAt(i))){
total = total + Integer.parseInt(fileData.charAt(i)+"");
}
}
System.out.println(total + " \n");
}
}
}