Retrieve numerical values from a text file

[Shikha Upadhyaya]

I have to retrieve numbers from a text file which has text as well as numbers. I have written the following code snippet just to check if I am able to print the numbers in the file.

try {
	Scanner myFile = new Scanner(new FileReader("C:/Documents and Settings/shikhau/workspace/SanNumber/freelast.txt"));
	while (myFile.hasNext()) {
		i = myFile.nextInt();
		System.out.println(i);
				
	}
}
catch (FileNotFoundException e){
          System.out.println("Sorry! This file is not found");
}

I get the following exception:

Exception in thread "main" java.util.InputMismatchException
	at java.util.Scanner.throwFor(Unknown Source)
	at java.util.Scanner.next(Unknown Source)
	at java.util.Scanner.nextInt(Unknown Source)
	at java.util.Scanner.nextInt(Unknown Source)

What do I do?

[John Jai]

Check if you are reading an integer with the hasNextInt() method

[Shikha Upadhyaya]

John Jai wrote:Check if you are reading an integer with the hasNextInt() method

Thanks. There is no exception thrown now. But there is no output either

[John Jai]

Show the code you modified and the text file contents you intend to read.

[John Jai]

Note the difference between next(), nextInt() and hasNext(), hasNextInt() methods. If you read the documentation the hasXXX() methods don't advance the scanner to the next position.

[Shikha Upadhyaya]

John Jai wrote:Show the code you modified and the text file contents you intend to read.

Complete code as of now:

package my.scan;
import java.util.*; //importing some java classes
import java.lang.*;
import java.io.*;

public class ScanNum {

	/**
	 * @param args
	 */
	
	public static void main(String[] args) {
		int i = 0;
		try {
				Scanner myFile = new Scanner(new FileReader("C:/Documents and Settings/shikhau/workspace/SanNumber/freelast.txt"));
				while (myFile.hasNextInt()) {
					i = myFile.nextInt();
					System.out.println(i);
				
				}
		}
		catch (FileNotFoundException e){
			System.out.println("Sorry! This file is not found");
		}
		
	}

}

Text file (freelast.txt) contents:

             total       used       free     shared    buffers     cached
Mem:          7923       7875         47          0        564       3237
-/+ buffers/cache:       4074       3848
Swap:        12287       1067      11220
Total:       20211       8943      11267

[Winston Gutkowski]

Shikha Upadhyaya wrote:Text file (freelast.txt) contents:

             total       used       free     shared    buffers     cached
Mem:          7923       7875         47          0        564       3237
-/+ buffers/cache:       4074       3848
Swap:        12287       1067      11220
Total:       20211       8943      11267

...

Well that should be a clue right there. What is the value of the first token that will be found by Scanner?

Winston

[Shikha Upadhyaya]

Winston Gutkowski wrote:
Well that should be a clue right there. What is the value of the first token that will be found by Scanner?

Winston

A blank space?

[John Jai]

Shikha Upadhyaya wrote:A blank space?

You could have printed that and seen
Now modify text file like below

123      total       used       free     shared    buffers     cached 

Check what happens after 123 is printed

[Shikha Upadhyaya]

John Jai wrote:
Check what happens after 123 is printed

123 is not printed at all!!! It's the same old blank space.

[John Jai]

I tried with the code you posted and got 123 printed... are you sure there is no blank token before that?

Anyways the way you try to print all numbers surrounded by strings in the text file is wrong.

1. Check if scanner has some thing to read using hasNext() in the while condition.

2. Check if the token pointed by the scanner is an integer using hasNextInt() method. Get it using nextInt() and print it. Note that nextInt() moves the scanner to the next position

3. If the condition failed for hasNextInt(), you got to move the scanner to the next position... just call the next() method of the scanner.

[Shikha Upadhyaya]

John Jai wrote:I tried with the code you posted and got 123 printed... are you sure there is no blank token before that?

Yes I am sure. I am using Eclipse Indigo. Well, that shouldn't affect the output in anyway.

John Jai wrote:Anyways the way you try to print all numbers surrounded by strings in the text file is wrong.

1. Check if scanner has some thing to read using hasNext() in the while condition.

2. Check if the token pointed by the scanner is an integer using hasNextInt() method. Get it using nextInt() and print it. Note that nextInt() moves the scanner to the next position

3. If the condition failed for hasNextInt(), you got to move the scanner to the next position... just call the next() method of the scanner.

Thanks, I will try this and post back.

[Shikha Upadhyaya]

Shikha Upadhyaya wrote:

John Jai wrote:I tried with the code you posted and got 123 printed... are you sure there is no blank token before that?

Yes I am sure. I am using Eclipse Indigo. Well, that shouldn't affect the output in anyway.

John Jai wrote:Anyways the way you try to print all numbers surrounded by strings in the text file is wrong.

1. Check if scanner has some thing to read using hasNext() in the while condition.

2. Check if the token pointed by the scanner is an integer using hasNextInt() method. Get it using nextInt() and print it. Note that nextInt() moves the scanner to the next position

3. If the condition failed for hasNextInt(), you got to move the scanner to the next position... just call the next() method of the scanner.

Thanks, I will try this and post back.

Hey it's working!!! Thanks a lot for all your replies. Thank you very much