Develop Reference

Printwriter not writing to file

output file is created but numbers are not written.
public static void main(String[] args)
{
String file_name;
String done_string = "done";
boolean done = false;
while (!done)
{
file_name = JOptionPane.showInputDialog("Enter a file name" + " or done to exit: ");
if (file_name.equals(done_string))
{
done = true;
JOptionPane.showMessageDialog(null, "EXITING");
}
else
{
try
{
File file_in = new File(file_name);
Scanner input = new Scanner(file_in);
JOptionPane.showMessageDialog(null, "File " + file_name + " found ");
int[] hold_ints = new int[100];
for (int i = 0; i< 100; i++)
{
hold_ints[i] = input.nextInt();
}
PrintWriter output = new PrintWriter("reverse_ints");
for (int i = 99; i <= 0; i--)
{
output.print(hold_ints[i]);
output.print(" ");
}
output.close();
input.close();
}
catch (FileNotFoundException e)
{
JOptionPane.showMessageDialog(null, "File " + file_name + " not found ");
}
}
}
}
}
Program should read a file then create an output file that prints the numbers in the input file in reverse.
Actual results just shows the file but nothing is written in the file.

For-loop condition is wrong, so code in the loop is not run.
I suppose it should be
for (int i = 99; i >= 0; i--)
{
output.print(hold_ints[i]);
output.print(" ");
}

Filtering specific team from text file and displaying results

I want my program to allow a user to enter a team name and based on that name it will distribute the pertinent team information to the console for viewing. So far, the program allows the user to input a text file that contains unformatted team data. It then formats that data, stores it and prints the information to the console. It is at this point in my program where I want the user to be able to start her/his filtering based on a team name. I am not necessarily looking for an exact answer but some helpful tips or suggestions would be appreciated.
public static void main(String[] args) {
Scanner keyboard = new Scanner (System.in);
// Allow the user to enter the name of text file that the data is stored in
System.out.println("This program will try to read data from a text file ");
System.out.print("Enter the file name: ");
String filename = keyboard.nextLine();
System.out.println();
Scanner fileReader = null;
//A list to add results to, so they can be printed out after the parsing has been completed.
ArrayList<LineResult> results = new ArrayList<>();
try {
File Fileobject = new File (filename);
fileReader = new Scanner (Fileobject);
while(fileReader.hasNext()) {
String line = fileReader.nextLine();// Read a line of data from text file
// this if statement helps to skip empty lines
if ("".equals(line)) {
continue;
}
String [] splitArray = line.split(":");
// check to make sure there are 4 parts in splitArray
if(splitArray.length == 4) {
// remove spaces
splitArray[0] = splitArray[0].trim();
splitArray[1] = splitArray[1].trim();
splitArray[2] = splitArray[2].trim();
splitArray[3] = splitArray[3].trim();
//This section checks if each line has any corrupted data
//and then display message to the user.
if("".equals(splitArray[0]))
{
System.out.println(line + " > The home or away team may be missing");
System.out.println();
}else if ("".equals(splitArray[1])) {
System.out.println(line + " > The home or away team may be missing");
System.out.println();
}
try {
// Extract each item into an appropriate variable
LineResult result = new LineResult();
result.homeTeam = splitArray[0];
result.awayTeam = splitArray[1];
result.homeScore = Integer.parseInt(splitArray[2]);
result.awayScore = Integer.parseInt(splitArray[3]);
results.add(result);
} catch(NumberFormatException e) {
System.out.println(line + " > Home team score may not be a valid integer number ");
System.out.println(" or it may be missing");
System.out.println();
}
}else {
System.out.println(line + " > The field delimiter may be missing or ");
System.out.println(" wrong field delimiter is used");
System.out.println();
}
}
System.out.println();
System.out.println();
//Print out results
System.out.println("Home team Score Away team Score");
System.out.println("========= ===== ========= =====");
//Loop through each result printing out the required values.
//TODO: REQ4, filter results based on user requested team
try (BufferedReader br = new BufferedReader(new File(filename));
BufferedWriter bw = new BufferedWriter(new FileWriter("data.txt"))) {
String line;
while ((line = br.readLine()) != null) {
String[] values = line.split(" ");
if (values.length >= 3)
bw.write(values[0] + ' ' + values[1] + ' ' + values[2] + '\n');
}
}
for (LineResult result : results) {
System.out.println(
String.format("%-15s %1s %-15s %1s",
result.homeTeam,
result.homeScore,
result.awayTeam,
result.awayScore));
}
// end of try block
} catch (FileNotFoundException e) {
System.out.println("Error - File does not exist");
System.out.println();
}
}
//Data object for holding a line result
static class LineResult {
String homeTeam, awayTeam;
int homeScore, awayScore;}
}

Troubles reading a single character from a text file

I'm writing an "app" that takes in time input from the user and stores the hours and the minutes separately for each day in a text file (giving a result that looks like:
day 1: 8h 45min
day 2: 8h 43min
... )
the idea behind it is to use this data for multiple stuff, like calculating the average time, or just accessing the time at any day, but I haven't reached that stage yet, I'm having troubles doing the simplest stuff like reading the hour and printing it.
here's the code
import java.util.Scanner;
import java.io.*;
public class TimeInput {
public static void main(String[] args) {
write();
read();
}
static void write() {
int dayOfMonth = 1;
String fileName = "time.txt";
int[] time = new int[2];
String timeDisplay;
Scanner s = new Scanner(System.in);
try {
FileWriter fileWriter = new FileWriter(fileName);
BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);
while (dayOfMonth <=31) {
System.out.println("Day " + dayOfMonth);
System.out.print("Enter hour: " + "__" + "h\r");
System.out.print("Enter hour: ");
time[0] = s.nextInt();
System.out.print("Enter minutes: " + "__" + "min\r");
System.out.print("Enter minutes: ");
time[1] = s.nextInt();
timeDisplay = ("\n"+ "day " + dayOfMonth + ": " + time[0] + "h " + time[1] + "min");
bufferedWriter.write(timeDisplay);
bufferedWriter.newLine();
dayOfMonth++;
if (time[0] == 0 && time[1] == 0) {
bufferedWriter.close();
dayOfMonth = 32; // break
}
}
}
catch (IOException ex) {
System.out.println(
"Error writing to file '" + fileName + "'");
}
}
static void read() {
String fileName = "time.txt";
String line = null;
try {
FileReader fileReader = new FileReader(fileName);
BufferedReader bufferedReader = new BufferedReader(fileReader);
while ((line = bufferedReader.readLine()) != null) {
char h = line.charAt(7);
System.out.println(h);
}
bufferedReader.close();
}
catch (FileNotFoundException ex) {
System.out.println(
"Unable to open file '" + fileName + "'" );
}
catch (IOException ex) {
System.out.println(
"Error reading file '" + fileName +"'");
}
}
}
I keep getting a String out of bounds exception and I don't understand why

You need to check empty string before char operation.
while ((line = bufferedReader.readLine()) != null) {
if("".equals(line)){
continue;
}
char h = line.charAt(7);
System.out.println(h);
}

Buffered Writer also saved enter key presses between your input. So to eliminate that enter presses add dummy readLine statement between each line read.
line=bufferedReader.readLine();
while ((line = bufferedReader.readLine()) != null) {
System.out.println(line);
char h = line.charAt(7);
System.out.println(h);
line=bufferedReader.readLine();
}

Take a look to the last loop.
Put a breakpoint and see what happen. Maybe the ArrayIndexOutBoundExceptions happens cuz youre trying to read more that one character and this cant be possible. Take a look to this url to see how to read a txt with bufferedReader.
http://www.mkyong.com/java/how-to-read-file-from-java-bufferedreader-example/
Hope this help.

Outputting to a closed stream?

So I fixed my program but the problem is that after replacing all the blank spaces with tildes i have to output the text to a file that has been closed. How would I re-open the file for output and input something in?
//Name: Allen Li
//Program file: Vowels.Java
//Purpose: Using File IO, read a file's input and output this text to a new text file
//When outputting, all blank spaces will be changed to tildes and there will be a count of each vowel(AEIOU)
import java.util.Scanner; //input
import java.io.File; //IO
import java.io.IOException; //IO exception class
import java.io.FileWriter; //file output
import java.io.FileReader; //file input
import java.io.FileNotFoundException; //if file isnt found, file not found class
public class Vowels { //class
public static void main(String[] args) { //main method
try { //try block
FileReader poetry = new FileReader("poetry.txt");
FileWriter dentist = new FileWriter(
"LI_ALLEN_dentist.txt");
int a;
while ((a = poetry.read()) != -1) {
dentist.write(a);
System.out.print((char) a); //print the file to the monitor
}
poetry.close();
dentist.close();
Scanner inFile = new Scanner(new File(
"LI_ALLEN_dentist.txt"));
int numOfVowelsA = 0; //count #s of A/E/I/O/U vowels
int numOfVowelsE = 0;
int numOfVowelsI = 0;
int numOfVowelsO = 0;
int numOfVowelsU = 0;
while (inFile.hasNext()) {
String sentence = inFile.next() /* ("\\S+") */;
for (int i = 0; i <= sentence.length() - 1; i++) {
if (sentence.toLowerCase().charAt(i) == 'a') {
numOfVowelsA++;
}
if (sentence.toLowerCase().charAt(i) == 'e') {
numOfVowelsE++;
}
if (sentence.toLowerCase().charAt(i) == 'i') {
numOfVowelsI++;
}
if (sentence.toLowerCase().charAt(i) == 'o') {
numOfVowelsO++;
}
if (sentence.toLowerCase().charAt(i) == 'u') {
numOfVowelsU++;
}
}
}
System.out.println();
System.out.println("There are " + numOfVowelsA
+ " A vowels in this file of text");
System.out.println("There are " + numOfVowelsE
+ " E vowels in this file of text.");
System.out.println("There are " + numOfVowelsI
+ " I vowels in this file of text.");
System.out.println("There are " + numOfVowelsO
+ " O vowels in this file of text.");
System.out.println("There are " + numOfVowelsU
+ " U vowels in this file of text. ");
Scanner tildes = new Scanner(new File(
"LI_ALLEN_dentist.txt"));
while (tildes.hasNext()) {
String replace = tildes.nextLine();
replace = replace.replaceAll(" ", "~");
System.out.println();
System.out.print(replace);
}
} catch (FileNotFoundException i) {
System.out.println("The file you are trying to use as input is not found. " + i);
} catch (IOException i) {
System.out.println("There is an issue with the input or output file. " + i);
}
}
}

You didn't close inFile. Close inFile first and then you are able to open it again in tildes.
Close it before Scanner tildes = new Scanner(...); line.

Output is not coming out correctly

The goal of this code is to read a file and add numbers to the end of every {(curly bracket) but the file does not output each line like it does in the file but it out puts it into one entire line. where do I put a System.out.println statement. I tried every where and it keeps repeating it
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class Test {
public static void main(String args[]) {
readFile();
}
public static void readFile() { // Method to read file
Scanner inFile = null;
String out = " ";
try {
Scanner input = new Scanner(System.in);
System.out.println("enter file name");
String filename = input.next();
File in = new File(filename); // ask for the file name
inFile = new Scanner(in);
int count = 0;
while (inFile.hasNextLine()) { // reads each line
String line = inFile.nextLine();
for (int i = 0; i < line.length(); i++) {
char ch = line.charAt(i);
out = out + ch;
if (ch == '{') {
count = count + 1;
out = out + " " + count + " ";
} else if (ch == '}') {
out = out + " " + count + " ";
if (count > 0) {
count = count - 1;
}
}
}
}
System.out.println(out);
} catch (FileNotFoundException exception) {
System.out.println("File not found.");
}
inFile.close();
}
}

where do I put a System.out.println statement
The entire output is built in a single string that is not printed until the end, so adding System.out.println statements in the line loop won't help. You can add line breaks to the string by doing:
out += "\n";
Or, at the end of the body of your line loop, print the current line, and reset the buffer for the next line:
System.out.println(out);
out = "";
Using a String for the output buffer is not efficient by the way. String is immutable, so every + statement is copying and duplicating all of the previous characters to create a new object, every time. Consider declaring out as a StringBuilder rather than a String. Then you can add to it with the .append() method and it will not copy all the text every time because a StringBuilder is mutable.