Returning array To Method

[Nick Rowe]

Hey Nicola,

Thanks for that, I thought that i was going to have to create another method to deal with it. Glad it wasn't.
My sisters rli not well, she didnt break anything but the docs did some tests on here and have noticed that shes got alot of bacteria in her bloody and some muscles damaged. Her bacteria count is supposed to be 8 and is sitting on average at around 113. She can barely walk so something is really wrong.
Hopefully after the scans etc come back they'll be able to sort things.

Thinking about something else entirely, is it easy to save the output from the program into a new file?
Hope your weekend was better at least the suns out today and we have some nice white clouds, its been horrible the last couple of days.
regards nick

[Nicola Garofalo]

it's as easy as reading it.

Here are some steps to follow, you will put code in to make things work

1)

build a method that receives the List and for example the file name

private void writeResults(List<String> list, String filename){
//...your method body
}

2)

Build a new File with the given filename String (look API documentation for File constructors)

3)

Create a PrintWriter around your File

4)

use PrintWriter methods to write your List elements (line by line if you need it)

5)

Finally flush and close the PrintWriter.

Let's see how you do this method. Enjoy

[Nick Rowe]

Thanks Nicola,
the examples im finding aren't that great, I've found an example that implements a try/catch method like in my program would i not use something along the lines of the example below, or is a method a more straight forward way?

So far I've just imported the necessary librarys and created a method, the other examples i found from the sun site weren't that helpful.
regards Nick

import java.io.FileReader;
import java.io.FileWriter;
import java.io.BufferedReader;
import java.io.PrintWriter;
import java.io.IOException;

public class CopyLines {
    public static void main(String[] args) throws IOException {
        BufferedReader inputStream = null;
        PrintWriter outputStream = null;

        try {
            inputStream = 
                new BufferedReader(new FileReader("xanadu.txt"));
            outputStream = 
                new PrintWriter(new FileWriter("characteroutput.txt"));

            String l;
            while ((l = inputStream.readLine()) != null) {
                outputStream.println(l);
            }
        } finally {
            if (inputStream != null) {
                inputStream.close();
            }
            if (outputStream != null) {
                outputStream.close();
            }
        }
    }
}

[Nicola Garofalo]

Your examples copies the content of one file into another file.
If that is what you want to do the example is right.

But if you want to put the elements of the ArrayList that you calculated in the previous steps in a file, just iterate through your ArrayList instead of through the lines of a BufferedReader, which, in that case, you could even delete.

[Nick Rowe]

So for example could I create a method like this below and then call it within the main body somewhere?

public static void writeResults (String[] args) throws IOException {     
        PrintWriter outputStream = null;   
  
        try {    
            outputStream =    
                new PrintWriter(new FileWriter("characteroutput.txt"));   
    
            while ((arrayList(resourceline)) != null) {   
                outputStream.println(resourceline);   
            }   
        } finally {    
            if (outputStream != null) {   
                outputStream.close();   
            }   
        }   
    } 

[Nicola Garofalo]

I don't understand your while condition at line 8.
Pass the ArrayList as an argument to your method, instead of an array of Strings. I wrote the signature of the method you need

private void writeResults(List<String> list, String filename){   
//...your method body   
}  

With your second argument you can pass to your method the file name to write into.

Then you should iterate through the ArrayList. You write line by line your file

for(String line:  list)
  outputStream.println(line);

[Nick Rowe]

Hi all,

So i've given my method a go and still having trouble but anyway heres what I have.
Also i realise that I still need to call my method on the command line
regards Nick

/**import java librarys*/
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.Collections;
import java.util.List;

/** class to find string */
public class Find {
	BufferedReader br = null;

	/** method to read html file line by line and return string to tore in array */
	public Find() throws java.io.IOException {
		try {
			/** read in file */
			br = new BufferedReader(
					new FileReader(
							"C:/Documents and Settings/Kieren McDonald/Desktop/Nick/Java/timelinemanager_resource.htm"));
			/**
			 * declaring string identifiers for beginning and end of string
			 * aswel as one other line string to store the data between
			 */
			String resourceline = null;
			String beg = "<@dynamichtml ";
			String end = "@>";
			ArrayList<String> arrayList = new ArrayList<String>();
			/** while line is not equal to null then find 3 string values */
			while ((resourceline = br.readLine()) != null) {
				resourceline = find(beg, end, resourceline);

				/**
				 * if line is not equal to null store line in array list adding
				 * a resource name
				 */
				if (resourceline != null) {
					resourceline= resourceline.trim();
					arrayList.add(resourceline);
				}

			}
			sortAndPrint(arrayList);
		} catch (FileNotFoundException ex) {
			ex.printStackTrace();
		} finally {
			br.close();
		}
	}

	/** method to sort and print the array collection */
	private void sortAndPrint(List<String> results) {
		Collections.sort(results,String.CASE_INSENSITIVE_ORDER);
		for (String resourceline : results)
			System.out.println(resourceline);
	}

	/** method to find the value between the beginning and end of a string */
	public String find(String beg, String end, String resourceline) {
		/** match pattern to store string between strings and match to line */
		Pattern p = Pattern.compile(beg + "(.*)" + end);
		Matcher m = p.matcher(resourceline);
		return m.find() ? resourceline.substring(m.start(1), m.end(1)) : null;
	}
	
	private void writeResults(ArrayList<String> arrayList, String filename) {   
    try {   
        PrintWriter writer = new PrintWriter( filename );   
  
        for (String resourceline : arrayList)   
            writer.println( resourceline );   
  
        writer.close();   
    }   
    catch( Exception e ) {   
        System.err.println( "can't create output file \"" + filename + "\"" );   
        e.printStackTrace();   
    }   
} 

	/** main method to find the resource name calling */
	public static void main(String[] args) throws IOException {
		Find findResources = new Find();
	}
}

[Nicola Garofalo]

Hi Nick,
you miss the import statement for PrintWriter

Whe you added it, call the method writeResults passing to it the ArrayList arrayList and a filename you chose to write to.
For example you could call that method at line 45 after the call to sortAndPrint method.

If you still have troubles, post the stack trace printed at runtime or the compile time error.

[Nick Rowe]

Ok done that, thanks Nicola

However when compiling the program i now get a compilation error which pops up when i call the writeResults method.

/**import java librarys*/
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.Collections;
import java.util.List;
import java.io.PrintWriter;
import java.io.FileWriter;


/** class to find string */
public class Find {
	BufferedReader br = null;

	/** method to read html file line by line and return string to tore in array */
	public Find() throws java.io.IOException {
		try {
			/** read in file */
			br = new BufferedReader(
					new FileReader(
							"C:/Documents and Settings/Kieren McDonald/Desktop/Nick/Java/timelinemanager_resource.htm"));
			/**
			 * declaring string identifiers for beginning and end of string
			 * aswel as one other line string to store the data between
			 */
			String resourceline = null;
			String beg = "<@dynamichtml ";
			String end = "@>";
			ArrayList<String> arrayList = new ArrayList<String>();
			/** while line is not equal to null then find 3 string values */
			while ((resourceline = br.readLine()) != null) {
				resourceline = find(beg, end, resourceline);

				/**
				 * if line is not equal to null store line in array list adding
				 * a resource name
				 */
				if (resourceline != null) {
					resourceline= resourceline.trim();
					arrayList.add(resourceline);
					
				}

			}
			sortAndPrint(arrayList);
			writeResults(arrayList);
		} catch (FileNotFoundException ex) {
			ex.printStackTrace();
		} finally {
			br.close();
		}
	}

	/** method to sort and print the array collection */
	private void sortAndPrint(List<String> results) {
		Collections.sort(results,String.CASE_INSENSITIVE_ORDER);
		for (String resourceline : results)
			System.out.println(resourceline);
	}

	/** method to find the value between the beginning and end of a string */
	public String find(String beg, String end, String resourceline) {
		/** match pattern to store string between strings and match to line */
		Pattern p = Pattern.compile(beg + "(.*)" + end);
		Matcher m = p.matcher(resourceline);
		return m.find() ? resourceline.substring(m.start(1), m.end(1)) : null;
	}
	
	private void writeResults(ArrayList<String> arrayList, String ResourceList) {   
    try {   
        PrintWriter writer = new PrintWriter( ResourceList );   
  
        for (String resourceline : arrayList)   
            writer.println( resourceline );   
  
        writer.close();   
    }   
    catch( Exception e ) {   
        System.err.println( "can't create output file \"" + ResourceList + "\"" );   
        e.printStackTrace();   
    }   
} 

	/** main method to find the resource name calling */
	public static void main(String[] args) throws IOException {
		Find findResources = new Find();
	}
}

[Nicola Garofalo]

it's easy to see. Look at the signature of the method and how you called it.
Anyway pay attention on what you do, you are not thinking about the problem, you are following instructions mechanically.
I told you that you must pass the filename to the writeResult method. Why don't you do it? Where do you expect the arraylist is written?

[Nick Rowe]

Morning Nicola,

I hope you had a nice weekend, although today seems to be a fight against the rain by the looks of it

Looking at the signature of the method, its called writeResults, which is what i've called, reading in the parameters of the filename and arraylist.
The way my mind was working was that I thought i would like to call in the arrayList to return and capture it and also the filename.
At first i simply used the "filename" as the parameter called but this also returned an error.
I realise this type of method is a private method, the same as the sortAndPrint which is called.

regards Nick x

[Nicola Garofalo]

The signature of writeResults method is

private void writeResults(ArrayList<String> arrayList, String ResourceList);

Look at how you call it:

writeResults(arrayList);

if you say that writeResult takes two arguments, why do you want to call it with just one? You can't. It won't work.

Look at the compiler message, it's explaining what you wanted to do (and you can't do).

[Nick Rowe]

Ok im completely with you, i've sorted that out, thank you.

Now when the program expires it only throws out two errors,


The first expecting a ) after String and the second declaring an illegal start of an expressiong because of the closing bracket at the end of the method call.

writeResults(ArrayList<String> arrayList, String filename);

Why would the compiler be expecting a closing bracket, and then the removal of another when the methods signature is the same? surely anything other than the correct name would throw an error?

I think the error in the compiler is simply suggesting where i should close the call but why would it do that knowing that it would be wrong?

regards Nick

[David Newton]

Are you saying there are still compilation errors?

If so, it'd be so much easier if you'd post the errors and the lines they correspond to.

[Nicola Garofalo]

You cannot call a method in that way

writeResults(ArrayList<String> arrayList, String filename); 

I have already told you that some posts ago. That's one of your first mistakes. Please go back and find it.

[Nick Rowe]

The error that comes up is on the line calling the writeResults method and details of the compiler error output are in the previous post with the string line attached.

Continuing with Nicolas previous post.
I have looked back and can see no error in my method call.

For example the method below contains the correct signature, its also executed with a semi-colon and contains both opening and closing brackets.

Unless you are suggesting to simply call the two parameters by using
writeResults(arrayList, filename);

This I have done, which only gives out the one error declaring that the compiler cannot find the string filename.

regards Nick

[David Newton]

There's no variable called "filename"--that's why it can't find it. You need to *provide* a filename, either in an immediate string, or in a variable.

And you can't just post a hundred lines of code and say "look at the line where writeResults is called". Well, you *can*, but it'd be much easier if you just posted the exact error message, and the line of code that it happens on. Why make it difficult for people to help you?

[Nick Rowe]

The error is called at line 50 which simply states that it cannot find the variable name filename.
however..
filename is a parameter of the method I am calling, aswel as arrayList. I simply left it the string name as filename for testing purposes.

The method below shows

private void writeResults(ArrayList<String> arrayList, String filename) {   
    try {   
        PrintWriter writer = new PrintWriter( filename );   
  
        for (String resourceline : arrayList)   
            writer.println( resourceline );   
  
        writer.close();   
    }   
    catch( Exception e ) {   
        System.err.println( "can't create output file \"" + filename + "\"" );   
        e.printStackTrace();   
    }   

regards Nick

[David Newton]

You may have a fundamental misunderstanding about how Java methods work.

The filename you show *there*, in the method definition, defines the parameter *within the method*. Not outside of it. If you *call* the method you must provide an argument--an actual value. The value may be immediate ("foo.txt") or a variable within the *current* scope. Simply using a variable called "filename" doesn't magically create one in the *current* scope.

[Nick Rowe]

Ahh apologies,
I simply thought that by using the parameter filename that it would generate a file of that such name.
So by using "filename.txt" within the call a new text file should be create?

Does this file also store within the same local directory as the program itself or is there a standard route folder like C:/programfiles/java that its stored in.

The reason that I ask is that I have tried this solution and although it compiles with no errors I cannot find the text file. No error message has come up informing me of the programs failure to write.

regards Nick

[David Newton]

A relative path will put the file in a directory relative to the execution context; I don't know how you're executing it, so I don't know where the file is.

[Nick Rowe]

I've now attempted to also use a direct reference for the new file
for example.

writeResults(arrayList, "C:\\Documents and Settings\\Kieren McDonald\\Desktop\\Nick\\Java\\Test\\filetest.txt");

The program compiles with no problems, however I cannot find the file anywhere.

regards Nick

[David Newton]

Any exceptions? I assume you looked in the path you listed rather than "anywhere", since there's only one place it would be.

[Nick Rowe]

Lol of course the referenced route folder is the only place i looked, initially i thought that the file would have been created locally to the java program that references it, however when a file was not created i took the previously mentioned approach. Unfortunately the file is still no where to be seen

[David Newton]

Then something else is wrong; check for exceptions, or look again for the file.