Extracting integers from a string.

I have a string as
How do I extract 98 and 100 and store them in an array. I wrote the following code:

It throws a NumberFormatException. What do I do?

Shikha Upadhyaya wrote:It throws a NumberFormatException. What do I do?

Catch the exception and ignore it. Only increment i when no exception is thrown.

StringTokenizer isn't a proper solution here. A Pattern / Matcher pair or a Scanner (where you can test for hasNextInt) are much better.

Rob Spoor wrote:StringTokenizer isn't a proper solution here. A Pattern / Matcher pair or a Scanner (where you can test for hasNextInt) are much better.

I tried hasNextInt also but I'm not able to make out where my code went wrong. So, thought of trying this out. It is also not working.

Shikha Upadhyaya wrote:

Rob Spoor wrote:StringTokenizer isn't a proper solution here. A Pattern / Matcher pair or a Scanner (where you can test for hasNextInt) are much better.

I tried hasNextInt also but I'm not able to make out where my code went wrong. So, thought of trying this out. It is also not working.

Can you please post the code you tried with hasNextInt()?

John Jai wrote:Can you please post the code you tried with hasNextInt()?

Below is the code:

package my.scan;  
import java.util.*; //importing some java classes  
import java.lang.*;  
import java.io.*;  
  
class ReadFile {
	void getFile () {
		int count = 0;
		int i;
		
	       try {  
	               Scanner fileScanner = new Scanner(new FileReader("C:/marks.txt"));  // This file contains first line as- "I have scored 98 on 100, 55 on 70.".
	               Scanner lineScanner;
	               String line;          
	               while (fileScanner.hasNextLine()) {  
	            	   line = fileScanner.nextLine();                
	            	    if (line.contains("I ")) {            	    		
	            	        while (fileScanner.hasNext()) { //Check if there is anything in the line
	            	        	if (fileScanner.hasNextInt() && count < 2) { //Extract just 98 and 100 and ignore the rest in that line
	            	        		System.out.println(fileScanner.nextInt());
	            	        		count++;
	            	        	}
	            	        	else {
	            	        		fileScanner.next();
	            	        	}
	            	        }          	    	
         	    	        lineScanner = new Scanner(line); 
	            	    }         
	               }  
	       }  
	       catch (FileNotFoundException e){  
	           System.out.println("Sorry! This file is not found");  
	       }
	}
}

public class ScanNum {  
    public static void main(String[] args) {  
        ReadFile rf = new ReadFile();
    	rf.getFile();
          
    }  
 
}

marks.txt:

You are having a scanner that scans the lines (lineScanner). But are you making use of that in your code?
The fileScanner shall be used only to read the file line by line. All operations (inner while loop, and the if and else inside it) you happen to do on the line do it on the line scanner.

There are couple more things I spotted but correct this one first.

John Jai wrote:
You are having a scanner that scans the lines (lineScanner). But are you making use of that in your code?
The fileScanner shall be used only to read the file line by line. All operations (inner while loop, and the if and else inside it) you happen to do on the line do it on the line scanner.

There are couple more things I spotted but correct this one first.

Got it!!! Thank you in helping me spot my mistakes.

The corrected code snippet follows:

try {    
                   Scanner fileScanner = new Scanner(new FileReader("C:/marks.txt"));  // This file contains first line as- "I have scored 98 on 100, 55 on 70.".  
                   Scanner lineScanner;  
                   String line;            
                   while (fileScanner.hasNextLine()) {    
                       line = fileScanner.nextLine();  
                        lineScanner = new Scanner(line);   
                        if (line.contains("I ")) {                            
                            while (lineScanner.hasNext()) { //Check if there is anything in the line  
                                if (lineScanner.hasNextInt() && count < 2) { //Extract just 98 and 100 and ignore the rest in that line  
                                    System.out.println(lineScanner.nextInt());  
                                    count++;  
                                }  
                                else {  
                                    lineScanner.next();  
                                }  
                            }                     
                           
                        }           
                   }    
           }    
           catch (FileNotFoundException e){    
               System.out.println("Sorry! This file is not found");    
           }

Welcome... two things...
1. You might need to set count to 0 before you start parsing each line.
2. Did you check whether 100, came as a integer token? Or it was ignored since it had a trailing comma?

Use System.out.println() to check which tokens were ignored...

John Jai wrote:Welcome... two things...
2. Did you check whether 100, came as a integer token? Or it was ignored since it had a trailing comma?

Use System.out.println() to check which tokens were ignored...

Oh yeah! 100 is not printed! I had given a space between 100 and , in the code earlier. What has to be done if 100 should be retrieved when it is 100, and not 100 , ?

One option is adding , as a delimiter along with the white space character to the scanner. Try adding the second line in the below code for the line scanner.

Ok.