Scanner

[Sumeet Chakraborty]

Can anyone explain me when do I get a "java.util.NoSuchElementException" while using Scanner class ?

I was practicing few Scanner examples, and I am getting the above exception many times. The following is one example. But I am not able to figure the reason out. Please help.

 String csv = "Abc,7,false,3";
		 Scanner scanner = new Scanner( csv );
         scanner.useDelimiter(",");
		 //int age = scanner.nextInt();

		 while(scanner.hasNext()){
			 System.out.println(scanner.next());
		 }
		 int a=scanner.nextInt();
                 System.out.println(a);

The following is the output of the above code block :

Abc
7
false
3
Exception in thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:838)
at java.util.Scanner.next(Scanner.java:1461)
at java.util.Scanner.nextInt(Scanner.java:2091)
at java.util.Scanner.nextInt(Scanner.java:2050)
at ScanTest.main(ScanTest.java:27)


Its clear that the program contains int values in the String and the Scanner is able to identify that, thats why it prints the values in the output above. But when i say int a=scanner.nextInt(); it throws the exception.

Please explain.

[Balu Sadhasivam]

Summet,

Can anyone explain me when do I get a "java.util.NoSuchElementException" while using Scanner class ?

there are many instances , anytime when there are no more input available to parse.

          while(scanner.hasNext()){  
              System.out.println(scanner.next());  
          }  
          int a=scanner.nextInt();  

here the while loop , you have exhausted your scanner , so there are no more inputs available when executing scanner.nextInt() . nextInt() would throw NoSuchElementException exception , when it encounters no elements

HTH

[Vinod Kumar Kommineni]

sumeet ,
try this code and it would work

  String csv = "1,7,8,3";  
	          Scanner scanner = new Scanner( csv );  
	          scanner.useDelimiter(",");  
	          //int age = scanner.nextInt();  
	   
	          //while(scanner.hasNext()){  
	         //    System.out.println(scanner.next());  
	         // }  
	          while(scanner.hasNext()){int a=scanner.nextInt();  
	                  System.out.println(a);  }
  

as balu said you reached the last element of the scanner and you don't have any next element to parse

[Morteza Manavi-Parast]

True. Try this one:

 import java.util.Scanner;

public class ScannerTest {

    public static void main(String[] args) {

         //String csv = "Abc,7,false,3";

        String csv = "ghi,7,def,3, abc,10";
		 Scanner scanner = new Scanner(csv);
         scanner.useDelimiter(",");
        /*
		 while(scanner.hasNext()){
			 System.out.println(scanner.next());
		 }
        */
         while(scanner.hasNext()){
             if (scanner.hasNextInt())
                 System.out.println(scanner.nextInt());
             else
                 scanner.next();
         }
    }

}
   

[Sumeet Chakraborty]

Thanks Balu for your reply.

But

here the while loop , you have exhausted your scanner

Can you please explain this.

I tried removing out the while loop , but still its throwing the same exception.

 

String csv = "Abc,7,false,3";
		 Scanner scanner = new Scanner( csv );
         scanner.useDelimiter(",");
		 int age = scanner.nextInt();

   

The output is :

Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Scanner.java:840)
at java.util.Scanner.next(Scanner.java:1461)
at java.util.Scanner.nextInt(Scanner.java:2091)
at java.util.Scanner.nextInt(Scanner.java:2050)
at ScanTest.main(ScanTest.java:22)


Kindly explain.

[Sumeet Chakraborty]

Thanks Morteza and Vinodkumar for your replies.

BTW Sorry, Its a different exception now. InputMismatchException. In the previous post I stated its the same exception.


I tried both Morteza and Vinodkumar's codes. Its giving the above exception at the line int age = scanner.nextInt();
Now why is this exception coming up ? I dont see any problem in that line .

And also please explain the concept of exhausting the scanner.

Thanks .

[Vinod Kumar Kommineni]

sumeet ,
i think you are trying to put a string into int, change the code

 String csv = "1,7,8,3";   

and try it ,if you get the same error please post

[Balu Sadhasivam]

Sumeet,

java.util.InputMismatchException would occur when there is no matching Integer and still you try to parse it. Check the API first.

here the while loop , you have exhausted your scanner

here i meant scanner has parsed all your input.

[Vinod Kumar Kommineni]

you are getting following lines of error
Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Scanner.java:840)
at java.util.Scanner.next(Scanner.java:1461)
at java.util.Scanner.nextInt(Scanner.java:2091)
at java.util.Scanner.nextInt(Scanner.java:2050)
at ScanTest.main(ScanTest.java:22)

because you are trying to parse a String into an int

and regarding the concept of exhausting basically you are reaching the end of the scanner ,that is the last element in the while loop itself .
so you don't have any more elements to scan

[Morteza Manavi-Parast]

I don't think you ran my code, cause I remove that age variable! It runs perfectly and display appropiate results.
A long as you check for nextInt(), you can give any combination of string and int that you want to the scanner.

[Sumeet Chakraborty]

Thanks everyone for your replies. But please dont mind me asking a silly question like this. Its was really confusing me a lot.
But now I am getting closer to get the actual picture.

What I understood is .... if I check the existence of next int values using the while loop and print the value using scanner.nextInt() , it is working fine.

 while(scanner.hasNext()){
		               if (scanner.hasNextInt())
		                   System.out.println(scanner.nextInt());
		               else
		                   scanner.next();
		           }   

but if I use int age = scanner.nextInt(); , its throwing the exception.

The Java API says the return type of the nextInt() method is int. So in the above case where I am using the age variable, it should assign the first available int value from the String to the variable age. But its not doing that.

So my question is , what is the exact reason for the exception when I am using the line int age = scanner.nextInt();

This may sound silly, but believe me I am somehow missing a small trick to explain this program to myself. So kindly help.

Thanks

[Vinod Kumar Kommineni]

Hi, sumeet
please modify your code as follows and try

while(scanner.hasNext()){  
	        	                          if (scanner.hasNextInt())  
	        	                        	  {int age = scanner.nextInt();
	        	                        	  System.out.println(age); } 
	        	                         else  
	        	                              scanner.next();  
	        	                     }      

you are trying to put the element in to an int with out checking weather its an int or not.
I think you will get it now

[Sumeet Chakraborty]

Thanks Vinodkumar. I got it.

Goodness me ... my mind was running on different track. I completely forgot that when the return type is unknown we have to check and cast it while assigning the value to a variable. I was thinking that ... if the int value exists in the String, then why not its getting assigned to the int variable.

Really it was silly from my side.

Thanks a ton everyone for your help.

[Vinod Kumar Kommineni]

some times it happens.. silly mistakes