File.exists() Problem

[Lio Liov]

I am dont know why I have this fileToOpen.exists()) problem
Thanks

import java.io.*;
import java.util.*;

public class FileReader {
	private String fileToOpen;
	private Scanner x;
	private ArrayList<String> values = new ArrayList<String>();

	public FileReader(String openFile) {
		fileToOpen = "jobs/" + openFile + ".txt";
		if (fileToOpen.exists()) {
			openFile();
			readFile();
		}
	}

	public ArrayList getArray() {
		return values;
	}

	private void openFile() {
		try {
			x = new Scanner(new File(fileToOpen));
		} catch (Exception e) {
			System.out.println("Job doesn't exist");
		}
	}

	private void readFile() {
		try {
			while (x.hasNext()) {
				String line = x.nextLine();
				String input = line.substring(line.indexOf(':') + 1);
				values.add(input);
			}

		} catch (Exception e) {
		}
	}
}

[Matthew Brown]

Well, it would be helpful in general if you told is what problem you were having.

But in this case, fileToOpen is a String, and exists() belongs to the File class, not String.

[Campbell Ritchie]

At least two other bits of poor style:

Your variables are not well named, eg x for a Scanner.

You have an empty catch, which means if an Exception occurs you will never know about it.

[Lio Liov]

Thanks,I redid my code .And I have this error
at java.util.ArrayList.get(Unknown Source)
at Test.main(Test.java:6)
How can I stop the object to be initialised if the file doesnt exist
Thanks

public class Test {
   public static void main(String[] args) {
		String job = "SeondJob";
		FileReader inp = new FileReader(job);
		System.out.println(inp.getArray().get(0));
		
	}
}

import java.io.*;
import java.util.*;

public class FileReader {
	private File fileToOpen;
	private Scanner x;
	private ArrayList<String> values = new ArrayList<String>();

	public FileReader(String openFile) {
		File f = new File("jobs/" + openFile + ".txt");
		if (!f.exists()) {
			System.out.println("The file doesnt exist");
		}
		else
		{
			fileToOpen=f;
			openFile();
			readFile();
		}
	}

	public ArrayList getArray() {
		
		return values;
	}

	private void openFile() {
		try {
			x = new Scanner(fileToOpen);
		} catch (Exception e) {
			System.out.println("Job doesn't exist");
		}
	}

	private void readFile() {
		try {
			while (x.hasNext()) {
				String line = x.nextLine();
				String input = line.substring(line.indexOf(':') + 1);
				values.add(input);
			}

		} catch (Exception e) {System.out.println("Problem");
		}
	}
}

[Campbell Ritchie]

What sort of error? A compiler error? A runtime error?
And why do you still have the empty catch block?

[Lio Liov]

Thanks
Run time error

at java.util.ArrayList.RangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at Test.main(Test.java:6)

I enter print into the exception

[Campbell Ritchie]

And what sort of Exception do you get? You can’t expect anybody to help if you withhold the details.

[Lio Liov]

Thanks
I specified the error in my previous post

at java.util.ArrayList.RangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at Test.main(Test.java:6)

[Matthew Brown]

That's where the exception occurs, not what it was.

[Lio Liov]

Thanks,
the exception occurs
System.out.println(inp.getArray().get(0));

[Campbell Ritchie]

That isn’t an Exception.
And have you get rid of that empty catch yet?

[Lio Liov]

Yes I did ,you can see it in the code above
How can I figurate the exception
Thanks

[Jeff Verdegan]

Lio wrote:
I specified the error in my previous post

at java.util.ArrayList.RangeCheck(Unknown Source)
at java.util.ArrayList.get(Unknown Source)
at Test.main(Test.java:6)

Matthew wrote:
That's where the exception occurs, not what it was.

Lio wrote:
the exception occurs
System.out.println(inp.getArray().get(0));

Lio, he's trying to tell you that all you've told us is where the exception occured, but you haven't told us which exception it is.
NullPointerException?
IOException?
StackOverflowError?

You've included some of the information that the error message provides, but not all of it.

[Lio Liov]

Thanks

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

[dennis deems]

Lio Liov wrote:Thanks

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

ArrayList throws this exception when someone tries to get an element that is out of range. So when index 0 is out of bounds it means the list is empty.

[Jeff Verdegan]

Lio Liov wrote:Thanks

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

Just like in your other thread, the error message is telling you everything you need to know: You are trying to access the first element (index 0) of an array that doesn't have any elements.

[fred rosenberger]

From your other thread, you have implied you are an absolute beginner, so just in case you haven't come across this...

If an array has a size of 0, there are no elements in it. But, elements are 0-base index. In other words, if an array has a size of 1, the one element is at position 0. If it has 10 elements, they are at positions 0-9.

So, your error tells you that you have an array of size 0. There are no elements in it. But you apparently try and access element 0 (the first element in the array). It's like me saying "Here is a box of envelopes. take out the first envelope and tell me what's in it." You open the box, and find there are NO elements in it, and you say "Hey - there aren't any envelopes, so I CAN'T tell you what's in the first one"

[Lio Liov]

thanks
What shall I do
-in the main check if the object is created

if(inp.getArray()!=null){
			System.out.println(inp.getArray().get(0));	
		}


or this

if(inp.getArray().size()!=0)

Or I can prevent somehow object to be created

[Jeff Verdegan]

Lio Liov wrote:thanks
What shall I do
-in the main check if the object is created

if(inp.getArray()!=null){
			System.out.println(inp.getArray().get(0));	
		}

That won't help at all. Null and empty are completely different. Null means the reference doesn't point to an object. Empty means the reference points to a List object, but that List doesn't have any elements.

(You may or may not still need the null test though, as a completely separate issue. Not having looked at your code, I can't say for sure one way or the other.)

if(inp.getArray().size()!=0)

That will test if it's empty, yes. If this is a java.util.Collection, such as ArrayList or LinkedList, then it also has an isEmpty() method.

Or I can prevent somehow object to be created

Huh?

[Campbell Ritchie]

Lio Liov wrote:Yes I did ,you can see it in the code above . . .

That is very bad practice, altering a post after it has been replied to.
Also simply printing "problem" helps you little. Change it to read

catch (Exception e)
{
   e.printStackTrace();
}

That is by no means good style, but it will give you useful information if you suffer an exception there.