Read specified portion text, from text file

[bob john]

This kind of scanners, scans everything.

package sprendimai;

	import java.io.File;
	import java.io.FileNotFoundException;
	import java.io.PrintWriter;
import java.util.Scanner;

	public class ScanerisIrprinteris {
	 
	    public static void main(String[] args) throws FileNotFoundException {
	 
	    	
	  
		       
	Scanner sn = new Scanner ( new File ("bag")    );
	while (   sn.hasNext () )
	{  String om = sn.nextLine ();
	   System.out.println ( om  );  }
		
	sn.close ();       
		       
		       
	    }
	}

However I need to modify this code somehow.
Text file "bag" contains.
On tree grows fruit: apples 11
In the shop lays fruit: bananas 6
Outside grows fruit: berries 5

And this is what I want get to console.
apples 11
bananas 6
berries 5

** Not modifying text file, there should be some kind of code settings.

[Knute Snortum]

You could just do a split on  ":" after reading a line.

[Campbell Ritchie]

Or find the index of ":" and take a substring.
Or use scanner1 to read each line. Pass the line to scanner2 using this constructor. Set scanner2's delimiter to ":" and call next() twice. Make both the Scanners local variables, then there will be no garbage collection issues. The delimiter is a regular expression. If you look in the Java™ Tutorials and scroll to the bottom of the page, you find that : is not a metacharacter, so you can use ":" without a \.

[bob john]

Scanner sn = new Scanner ( new File ("bag")    );
	while (   sn.hasNext () )
	{  String om = sn.nextLine ();
	   String Str = new String(":");
	   System.out.print("Return Value :" );
	   System.out.println(Str.substring(10) );
	   
	   System.out.println ( om  );  }
		
	sn.close ();       
		            
	    }
	}

The console shows error:
Return Value :Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -9
at java.lang.String.substring(Unknown Source)
at sprendimai.ScanerisIrprinteris.main(ScanerisIrprinteris.java:27)

[Campbell Ritchie]

Read the documentation for substring and see whether it says anything about that sort of Exception.
Don't use Capital Letters for variables. Not Str but str.
Don't use new String(":"). Use = ":"

[Winston Gutkowski]

bob john wrote:

Scanner sn = new Scanner ( new File ("bag")    );
	while (   sn.hasNext () )
	{  String om = sn.nextLine ();
	...

Problem: Whenever you use a 'next....' method, you should use its associated 'hasNext...' method.
What do you think that might be?

Winston

[bob john]

Problem: Whenever you use a 'next....' method, you should use its associated 'hasNext...' method.
What do you think that might be?

Winston

???

[fred rosenberger]

You should only call the next method if the thing you are iterating through actually has a next item to get.

Also, i would suggest that variables like "om" and "str" are poor choices for variable names.  Your not IMing someone. You have a full keyboard. Use descriptive names so you know what the variable represents.

[bob john]

fred rosenberger wrote:You should only call the next method if the thing you are iterating through actually has a next item to get.

Also, i would suggest that variables like "om" and "str" are poor choices for variable names.  Your not IMing someone. You have a full keyboard. Use descriptive names so you know what the variable represents.

Yet I dont write projects, nor doing some kind of homewok plan.

Im learning and writing short codes. They are common and generic, in overall expired of imagination.

[Knute Snortum]

Problem: Whenever you use a 'next....' method, you should use its associated 'hasNext...' method.  

It's not very clear from the documentation, but you need to pair the hasNextXXX() method with its corresponding nextXXX() method.  So if you check for hasNext(), you need to get with next().  If you check with hasNextLine() you need to get with nextLine() and so on.

[Knute Snortum]

bob john wrote:

fred rosenberger wrote:Also, i would suggest that variables like "om" and "str" are poor choices for variable names.  Your not IMing someone. You have a full keyboard. Use descriptive names so you know what the variable represents.

Yet I dont write projects, nor doing some kind of homewok plan.

Im learning and writing short codes. They are common and generic, in overall expired of imagination.

Even if this is a personal project, you should get in the habit of using descriptive variables names.  It may even help yourself in the future!

[bob john]

Yet I struggle to learn basic codes to write, its too far for me to start project. And the porblem is that no one solved my task.
Java docs provide inacurate codes, or somehow complex algorith with "try.catch" what I have not learned.

[Knute Snortum]

Okay, what's the problem now?  You're having trouble with a try/catch?  Can you post the code?

[bob john]

Knute Snortum wrote:Okay, what's the problem now?  You're having trouble with a try/catch?  Can you post the code?

http://docs.oracle.com/javase/tutorial/essential/io/file.html

I have not learned it yet.

[Paul Clapham]

bob john wrote:

Knute Snortum wrote:Okay, what's the problem now?  You're having trouble with a try/catch?  Can you post the code?

http://docs.oracle.com/javase/tutorial/essential/io/file.html

I have not learned it yet.

Then you shouldn't be writing programs which use files, because they need to use exceptions. Perhaps you're getting ahead of yourself in whatever you're learning from?

[Knute Snortum]

But you're using File() just fine in your program.  

[bob john]

Knute Snortum wrote:But you're using File() just fine in your program.  

If I run the program, console will display:

On tree grows fruit: apples 11
In the shop lays fruit: bananas 6
Outside grows fruit: berries 5

What I want to get?
This is what I want to get in console, without modify text file:

apples 11
bananas 6
berries 5

------------------------------------------
Text file contains text:

On tree grows fruit: apples 11
In the shop lays fruit: bananas 6
Outside grows fruit: berries 5

[Winston Gutkowski]

bob john wrote:If I run the program, console will display:
On tree grows fruit: apples 11
....
What I want to get? This is what I want to get in console, without modify text file:
apples 11
...

OK, that's a good description of what you want to see, but you actually have TWO problems:
1. You need to read lines from a text file.
2. You need to extract the above information from EACH line.

It appears that you've solved the first problem, but you're having problems with the second one. So, eliminate the first one and concentrate on the second.

My suggestion: Write a completely new program that looks something like this:

public class LineDisplay {
   public static void main(String[] args) {
      final String line = "On tree grows fruit: apples 11";
            // the 'final' stops you from changing 'line'

      String display;

      // Logic to extract what you want from 'line' and
      // put it in 'display'

      System.out.println(display);
   }
}

Do you see the idea?

Now you have a program that deals specifically with the problem you want to solve, and you can test it with any "sample" line you like by simply changing the literal for 'line' and running it.

You've already been given several suggestions as to how to do it, so I suggest you re-read the previous posts in this thread

And as soon as this program works - every time - you can take its logic and copy it into your other one.

It's called "problem isolation", and its a technique we all use when we have problems.

HIH

Winston

[bob john]

Providing current stance.

And how result should look like.

[Henry Wong]

bob john (assumed via image) wrote:I need some kind of arguments / parameters. To make scanner scan only desired part of text file.

Since you are currently learning Java, I recommend following what others have already stated. Treat the task as two separate tasks. Use the Scanner to read in a single line, and then parse that line for the part that you want.


Yes, the scanner class is capable of doing what you want, as it is built with access to the regular expression engine (that is being used to scan for the tokens). However, regexes is *not* a beginner topic. So, unless Java is not your first language, and you already know regular expressions from previous experience, using the scanner to do this is not recommended here.

Henry

[Knute Snortum]

Knute Snortum wrote:You could just do a split on  ":" after reading a line.

Campbell Ritchie wrote:Or find the index of ":" and take a substring.

[bob john]

Knute Snortum wrote:

Knute Snortum wrote:You could just do a split on  ":" after reading a line.

Campbell Ritchie wrote:Or find the index of ":" and take a substring.

package DO;

import java.io.FileReader;
import java.io.IOException;
import java.util.Scanner;

public class ArrL {

	public static void main(String[] args) throws IOException {
		
	
		FileReader file = new FileReader ("just");
		
		Scanner reader = new Scanner (file);
		
		while (  reader.hasNext (":") ) {
		
			String line = reader.nextLine (); 
                        line. split (": ");
			System.out.println (line ); }
	
	 reader.close ();
		
	}

}

I have Inserted ":" in 16th line. Now console is completely empty, no errors too.

[Carey Brown]

split() returns a result that you are throwing away. I suggest reading up on split() in the API javadocs.
http://docs.oracle.com/javase/8/docs/api/java/lang/String.html#split-java.lang.String-

[bob john]

Carey Brown wrote:split() returns a result that you are throwing away. I suggest reading up on split() in the API javadocs.
http://docs.oracle.com/javase/8/docs/api/java/lang/String.html#split-java.lang.String-

I dont understand, not even single example.

[Carey Brown]

What does this return?

public String[] split(String regex)

In your case the regex would be ": ". This will split the string when it encounters a colon followed by a space.

[bob john]

Carey Brown wrote:What does this return?

???

public String[] split(String regex)

In your case the regex would be ": ". This will split the string when it encounters a colon followed by a space.

Where?

[Carey Brown]

See: http://www.homeandlearn.co.uk/java/java_methods.html

From this you should get the basic layout for specifying a method. Specifically you should note how the return type is declared. From that you should be able to say what the return type of this is...

public String[] split(String regex)

I just clipped this out of the Java API documentation. As you go forward you'll need to be able to interpret these documents, maybe not all of it, but certainly the signature of a method (i.e. what parameters it takes and what type it returns).

Have you learned arrays yet? Perhaps you're not up for this yet.

[Carey Brown]

How much have you looked at the methods of the String class? Another approach would be to use the indexOf() and substring() methods.

[Sergiu Dobozi]

Here is a simple code that I wrote in about ten minutes (I know it's a lot, but I'm still a beginner). It doesn't solve your problem, but if you understand it, and you can apply the logic, I'm sure you can figure out the solution to your problem.

String sentence = "I have fun with Java: Shoot me now";
String[] sentenceArray = sentence.split(":");
System.out.println(sentenceArray[1]);

[bob john]

Sergiu Dobozi wrote:Here is a simple code that I wrote in about ten minutes (I know it's a lot, but I'm still a beginner). It doesn't solve your problem, but if you understand it, and you can apply the logic, I'm sure you can figure out the solution to your problem.

String sentence = "I have fun with Java: Shoot me now";
String[] sentenceArray = sentence.split(":");
System.out.println(sentenceArray[1]);

My hero.

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.util.Scanner;

public class ScanerisIrprinteris {
  
    public static void main(String[] args) throws FileNotFoundException {
  
      
   
            
Scanner sn = new Scanner ( new File ("just")    );
while (   sn.hasNext () )
		{  String om = sn.nextLine ();
		String[] sentenceArray = om.split(":");


		System.out.println ( sentenceArray[1]  );  }
     
sn.close ();       
            
            
    }
}

[Knute Snortum]

You really need to correct your formatting, especially your while loop.