Java newbie here!
I'm writing a program to practice reading input and writing output to files. I've finished coding the program, but when I run it, the program just catches and proceeds with a FileNotFoundException.
The file is in the source folder for the program, and I've even tried placing it in every folder related to the program. I've tried:
Declaring the exceptions in the method header
Surrounding the section-in-question with a try/catch block.
Both of the above together.
Here's the relevant code that is causing problems. Is there something that sticks out that I'm missing?
public static void main(String[] args) throws FileNotFoundException {
Scanner keyboard = new Scanner(System.in);
String playerHighestScore = "", playerLowestScore = "";
int numPlayers = 0, scoreHighest = 0, scoreLowest = 0;
System.out.println("Enter an input file name: ");
String inputFileName = keyboard.nextLine();
String outputFileName = getOutputFileName(keyboard, inputFileName);
File inputFile = new File(inputFileName);
try {
Scanner reader = new Scanner(inputFile);
reader.close();
}
catch (FileNotFoundException exception) {
System.out.println("There was a problem reading from the file.");
System.exit(0);
}
Scanner reader = new Scanner(inputFile);
PrintWriter writer = new PrintWriter(outputFileName);
The answer is simple. If you get a FilENotFoundException, obviously the reason is File Not Found in the given path.
If you use an IDE, path for the working directory is different from the source directory.
For example, if you are using NetBeans, your source files are inside /src. But your working directory (.) is the project directory.
In the other hand, the problem may be the thing that #Don mentioned. If you are going for a cross platform approach, you can use "/" in paths. It works irrespective to the OS.
Example : String fileName = "C:/Directory/File.txt";
And these paths are case sensitive. So make sure you use the correct case. (It won't be a problem in Windows, until you package the program.)
Related
I'm trying to get my program to read data from a text file and store it in an array. The text file contains data about a planet.
Here is an example:
Mercury
4.151002e10
2.642029e10
-1.714167e9
-3.518882e4
4.355473e4
6.785804e3
3.302e23
My file is named test.txt. It lives in the same directory as my class.java file. I've used System.out.println(new File("test.txt").getAbsolutePath()); to check if the directory path is correct, which it was, and I used System.out.println(new File(".")); to check if it was in the same directory that the code was trying to compile in, which again it was (outputted just a dot which I was led to believe meant it was in the correct directory). I've tried different ways of finding the file, such as renaming it to something else to check it wasn't a keyword, changing the encoding of the file to Unicode, or UTF-8, or ANSI, none of which worked, using .\test in the file to look in the same directory, none of which worked.
Here is my code:
public static void defaultPlanetArray(){
Planet[] solarSystem;
solarSystem = new Planet[9];
PhysicsVector dummyAcceleration = new PhysicsVector();
System.out.println(new File("test.txt").getAbsolutePath());
System.out.println(new File("."));
try{
File file = new File("C:\\Users\\Lizi\\Documents\\Uni Work\\Year 2\\PHYS281\\Project\\test.txt");
Scanner scnr = new Scanner(file);
}
catch(FileNotFoundException e){
System.out.println("File not found!");
}
int i = 0;
while(i<9 && scnr.hasNextLine()){
//read values from file and set as Planet object, then set to array.
i++
}
PhysicsVector and Planet are both classes I have created. PhysicsVector and the rest of Planet apart from this excerpt compile with no problems. When I try to compile this specific bit of code, I get:
.\Planet.java:65: error: cannot find symbol
while(i<9 && scnr.hasNextLine()){
^
I'm guessing this means that the variable scnr is not being created in the try section because it cannot find the file. I think this because when I don't include the try and catch blocks, I get:
.\Planet.java:59: error: unreported exception FileNotFoundException; must be caught or declared to be thrown
Scanner scnr = new Scanner(file);
^
I've also tried the catches FileNotFoundException when I'm first creating the method but that gives me the same error as immediately above.
I could just set the values in the program, but that would give a lot of unnecessary code and be rather inefficient I think.
So my question is, how do I get the scanner to read my values from the file?
As #Lalit Verma pointed the scnr variable you defined lives inside the try - catch block.
Change the code to:
try{
File file = new File("C:\\Users\\Lizi\\Documents\\Uni Work\\Year 2\\PHYS281\\Project\\test.txt");
Scanner scnr = new Scanner(file);
int i = 0;
while(i<9 && scnr.hasNextLine()){
//read values from file and set as Planet object, then set to array.
i++
}
}catch(FileNotFoundException e){
System.out.println("File not found!");
}
I am a beginner Java student, working on our first class assignment.
In this assignment, I need to read a txt file, and fill an array with its contents, first space in the array per line.
My professor gave us code to do this, but I keep getting an error that the file cannot be read each time I try.
I am using Netbeans 8, on a Mac, and the file States.Fall2014.txt is located in the src folder, with all of my java classes.
Exception in thread "main" java.io.FileNotFoundException: States.Fall2014.txt (No such file or directory)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:138)
at java.io.FileInputStream.<init>(FileInputStream.java:93)
at java.io.FileReader.<init>(FileReader.java:58)
at main.main(main.java:21)
Java Result: 1
Here is the code I have. I have only included the code that pertains to opening the file, as I'm sure you have no wish to be spammed with the other classes.
The commented code during the trimming is to echo print, to make sure the file is being read in properly (not currently needed since the file isn't being read in at all).
import java.io.*;
public class main {
/**
* #param args the command line arguments
* #throws java.io.IOException
*/
public static void main(String args[]) throws IOException {
StateCollection Sdriver = new StateCollection(50);
//Sdriver = new StateCollection(50);
//Creates object of collection class
FileReader fr= new FileReader("States.Fall2014.txt");
BufferedReader br1 = new BufferedReader (fr);
String inputString;
String stateName;
String stateCapital;
String stateAbbrev;
int statePop;
String stateRegion;
int stateRegionNum;
inputString = br1.readLine();
while (inputString != null)
{
stateName = inputString.substring(1, 15).trim();
//System.out.println("stateName read in was: " + stateName);
stateCapital = inputString.substring(16, 30).trim();
//System.out.println(“stateCapital read in was: “ + stateCapital);
stateAbbrev = inputString.substring(31, 32).trim();
//System.out.println(“stateAbbrev read in was: “ + stateAbbrev);
statePop = Integer.parseInt(inputString.substring(33, 40));
//System.out.println(“statePop read in was: “ + statePop);
stateRegion = inputString.substring(41, 55).trim();
//System.out.println(“stateRegion read in was: “ + stateRegion);
stateRegionNum = Integer.parseInt(inputString.substring(56));
//System.out.println(“stateRegionNum read in was: “ + stateRegionNum);
//Code to create object
inputString = br1.readLine(); // read next input line.
}
br1.close(); //Close input file being read
Change
FileReader fr= new FileReader("States.Fall2014.txt");
to
FileReader fr= new FileReader("src/States.Fall2014.txt");
or move the file up one level to the project directory.
Make sure that the TXT file is in the right folder/area.
You shouldn't have it with your class, as the other answer states, you need it in the root folder.
Move the file up one level, to the same as the src folder.
The src directory is not (necessarily) the directory the .class file is in. Make sure States.Fall2014.txt is on the class-path.
I am new to Java , I am currently analyzing a file compare tool with java that compare two files from this link:
http://www.java2s.com/Code/Java/File-Input-Output/Difftextfiledifferenceutility.htm
But no where in the file, the file path is mentioned. Where should I insert the file path? I searched google and checked Java Filestram and buffer input output stream. But did not found any useful information.
I also searched stackoverflow but it seems no such question exists.
Usually, the file path should be updated in main file, right?
But it seems that is missing in main file.
public static void main(String argstrings[])
{
if ( argstrings.length != 2 ) {
System.err.println("Usage: diff oldfile newfile" );
System.exit(1);
}
Diff d = new Diff();
d.doDiff(argstrings[0], argstrings[1]);
return;
}
Your program takes the file names as the parameter. So while giving the command line input you can give the full file paths. Something like this:
java yourClassName volume1:\dir1\filename1 volume2:\dir2\filename2
You can certainly do the way juned told you but if you want to the program to be more user friendly try to manipulate the main method like this
public static void main(String[] args) throws ParseException {
try{
Scanner in = new Scanner(System.in);
System.out.println("Enter the path of old file");
String oldFile = in.nextLine();
System.out.println("Enter the path of new file");
String newFile = in.nextLine();
Diff d = new Diff();
if(!oldFile.equals("") && !newFile.equals("")) {
d.doDiff(oldFile, newFile);
}
}
catch (Exception e){
e.printStackTrace();
}
}
I have a file which is needed for running tests - this file needs to be personalized (name and password) by whomever is running the test. I do not want to store this file in Eclipse (since it would need to be changed by whomever runs the test; also it would be storing personal info in the repo), so I have it in my home folder (/home/conrad/ssl.properties). How can I point my program to this file?
I've tried:
InputStream sslConfigStream = MyClass.class
.getClassLoader()
.getResourceAsStream("/home/" + name + "/ssl.properties");
I've also tried:
MyClass.class.getClassLoader();
InputStream sslConfigStream = ClassLoader
.getSystemResourceAsStream("/home/" + name + "/ssl.properties");
Both of these give me a RuntimeException because the sslConfigStream is null. Any help is appreciated!
Use a FileInputStream to read data from a file. The constructor takes a string path (or a File object, which encapsulates string path).
Note 1: A "resource" is a file which is in the classpath (alongside your java/class files). Since you don't want to store your file as a resource because you don't want it in your repo, ClassLoader.getSystemResourceAsStream() is not what you want.
Note 2: You should use a cross-platform way of getting a file in a home directory, as follows:
File homeDir = new File(System.getProperty("user.home"));
File propertiesFile = new File(homeDir, "ssl.properties");
InputStream sslConfigStream = new FileInputStream("/home/" + name + "/ssl.properties")
You can simplify your work, using Java's 7 method:
public static void main(String[] args) {
String fileName = "/path/to/your/file/ssl.properties";
try {
List<String> lines = Files.readAllLines(Paths.get(fileName),
Charset.defaultCharset());
for (String line : lines) {
System.out.println(line);
}
} catch (IOException e) {
e.printStackTrace();
}
}
You can also improve your way of reading properties file, using Properties class and forget about reading and parsing your .properties file:
http://www.mkyong.com/java/java-properties-file-examples/
Is this a graphics program (ie. using the Swing library)? If so it is a pretty simple task of using a JFileChooser.
http://docs.oracle.com/javase/6/docs/api/javax/swing/JFileChooser.html
JFileChooser f = new JFileChooser();
int rval = f.showOpenDialog(this);
if (rval == JFileChooser.APPROVE_OPTION) {
// Do something with file called f
}
You can also use Scanner to read the file.
String fileContent = "";
try {
Scanner scan = new Scanner(
new File( System.getProperty("user.home")+"/ssl.properties" ));
while(scan.hasNextLine()) {
fileContent += scan.nextLine();
}
scan.close();
} catch(FileNotFoundException e) {
}
I am very new at java and my be missing something very basic. When i run my code i am trying to add value to accounts created in the code. When i try to run the code i recieve an error that a file cannot be found, but i thought that the file was created inside the code.
import java.util.Scanner;
import java.io.File;
import java.io.IOException;
class DoPayroll
{
public static void main(String args[])
throws
IOException
{
Scanner diskScanner =
new Scanner(new File("EmployeeInfo.txt"));
for (int empNum = 1; empNum <= 3; empNum++)
{
payOneEmployee(diskScanner);
}
}
static void payOneEmployee(Scanner aScanner)
{
Employee anEmployee = new Employee();
anEmployee.setName(aScanner.nextLine());
anEmployee.setJobTitle(aScanner.nextLine());
anEmployee.cutCheck(aScanner.nextDouble());
aScanner.nextLine();
}
}
once run i recieve the following error
Exception in thread "main" java.io.FileNotFoundException: EmployeeInfo.txt (No such file or directory)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:106)
at java.util.Scanner.<init>(Scanner.java:636)
at DoPayroll.main(jobexe.java:11)
i thought that in the above code using new Scanner(new File("EmployeeInfo.txt") would create the new file once i input a value. Please give me a simple solution and an explanation.
It will create a new file when you write to it. However to read from it, it must already exist. You might like to check it exists with
File file = new File("EmployeeInfo.txt");
if (file.exists()) {
Scanner diskScanner = new Scanner(file);
for (int empNum = 1; empNum <= 3; empNum++)
payOneEmployee(diskScanner);
}
The File object can't find the filename you've passed. You either need to pass the full path of EmployeeInfo.txt to new File(...) or make sure current working directory is the directory that contains this file.
The File constructor does not create a file. Rather, it creates the information in Java needed to access a file on disk. You'd have to actually do file IO in Java using the created File for a new file to be created.
The Scanner constructor requires an existing File. So you need a full path to the real, valid location of EmployeeInfo.txt or to create that file using File I/O first. This tutorial on I/O in Java will help.
You are mistaking instantiating an instance of class File with actually writing a temp file to Disk. Take this line
Scanner diskScanner =
new Scanner(new File("EmployeeInfo.txt"));
And replace it with this
File newFile = File.createTempFile("EmployeeInfo", ".txt");
Scanner diskScanner = new Scanner(newFile);
Edit: Peter makes a good point. I'm face palming right now.
You thought wrong :D A Scanner needs a existing file, which seems quite logical as it reads values and without a existing file its difficult to read. The documentation also states that:
Throws:
FileNotFoundException - if source is not found
So, in short: You must provide a readable, existing file to a scanner.
As the other answer explain, the file is not created just by using new File("EmployeeInfo.txt").
You can check is the file exists using
File file = new File("EmployeeInfo.txt");
if(file.exists()) {
//it exists
}
or you can create the file (if it doesn't exists yet) using
file.createNewFile();
that method returns true if the file was created and false if it already existed.