Question about NoSuchElementException thrown from scanner.next().charAt(0)

[OmegaNine]

I have searched around but not found an answer. It may be due to my inexperience and not understanding how it is applied to my situation. If so I apologies in advance.

I am trying to pull the first char of a user entered string using java.util.Scanner. When I enter a char and press enter at run time I get "java.util.NoSuchElementException" in the line "type = input.next().charAt(0);". I have tried both .next() and .nextLine()

The method contains the error is below. It is a practice assignment in a book, and my teacher can't give me an answer so I thought I would ask here.

	private static char GetTempType(){
                //Setting up vars and Scanner for input
		char type = ' ';
		boolean notSet = true;
		Scanner input = new Scanner(System.in);
		
                //This looks will keep going until the user enters a valid entry. 
		while(notSet){
			System.out.print("Would you like to convers to (C)elsius to (F)ahrenheit?");
			type = input.next().charAt(0);
			
			if(type == 'C' || type == 'c'){
				type = 'C';
				notSet = false;
			}else if(type == 'F' || type == 'f'){
				type = 'F';
				notSet = false;
			}else{
				System.out.println("Not a valid entry.");
			}
		}//End While loop
		input.close();
		
		return type;
	}//end GetTempType

From what I can see 'NoSuchElementException" is saying that the charAt(0) is trying to pull from a null object, but I have used this method of user input before with no problem. I am confused. Anyone see my newbie mistake?

Thanks in advance.

[eRaaaa]

Can you give us a small runnable example with main method and so on? The code above runs fine here....

	public static void main(String... args) throws Exception {
		char type = ' ';
		boolean notSet = true;
		Scanner input = new Scanner(System.in);

		// This looks will keep going until the user enters a valid entry.
		while (notSet) {
			System.out
					.print("Would you like to convers to (C)elsius to (F)ahrenheit?");
			type = input.next().charAt(0);

			if (type == 'C' || type == 'c') {
				type = 'C';
				notSet = false;
			} else if (type == 'F' || type == 'f') {
				type = 'F';
				notSet = false;
			} else {
				System.out.println("Not a valid entry.");
			}
		}// End While loop
		input.close();

	}

[OmegaNine]

Here is the full program. The problem occurs in the first method called, its a big paste, but mostly just filler for the problem.

package temp;

import java.util.Scanner;

public class Temp {

	public static void main(String[] args) {
		char type = ' ';
		double userTemp = 0;
		double convertedTemp = 0;
		
		type = GetTempType();
		userTemp = GetTemp(type);
		
		switch (type){
		case 'F': convertedTemp = ConvertCtoF(userTemp); break;
		case 'C': convertedTemp = ConvertFtoC(userTemp); break;
		}
		
		DisplayResults(convertedTemp, type);

	}//End main
	
	//Parameters: double - temp
	//			  char - temp type
	//Returns: void
	private static void DisplayResults(double temp, char type){
		
		if(type == 'F'){
			System.out.println("The temperature in Farenheit: " + temp);
		}else if(type == 'C'){
			System.out.println("The temerature in Celcius: " + temp);
		}
	}//ENd DisplayResults
	
	//Parameters: double - Farenheit temp
	//Returns: double - Celcius temp
	private static double ConvertCtoF(double tempC){
		double tempF = tempC * 1.8 + 32;
		return tempF;
	}//end ConvertCtoF
	
	//Parameters: double - Celsius temp
	//Returns: double - Farenheit temp
	private static double ConvertFtoC(double tempF){
		double tempC = (tempF - 32) / 1.8;
		return tempC;
	}//end ConvertFtoC
	
	//Parameters: char - F or C (For types of temps)
	//Returns: double - Entered Temp
	private static double GetTemp(char type){
		double temp = 0;
		
		Scanner input = new Scanner(System.in);
		
		if(type == 'C'){
			System.out.print("Please enter the temperature in Fahrenheit: ");
			temp = input.nextDouble();
		}else if(type == 'F'){
			System.out.print("Please enter the temperature in Celcius: ");
			temp = input.nextDouble();
		}
		
		input.close();
		
		return temp;
	}//End GetTemp
	
	//prompts and reads a char from user, then returns a cleaned version
	private static char GetTempType(){
		char type = ' ';
		boolean notSet = true;
		Scanner input = new Scanner(System.in);
		
		while(notSet){
			System.out.print("Would you like to convers to (C)elsius to (F)ahrenheit?");
			type = input.next().charAt(0);
			
			if(type == 'C' || type == 'c'){
				type = 'C';
				notSet = false;
			}else if(type == 'F' || type == 'f'){
				type = 'F';
				notSet = false;
			}else{
				System.out.println("Not a valid entry.");
			}
		}//End While loop
		input.close();
		
		return type;
	}//end GetTempType

}

[eRaaaa]

Ok, it seems that the second Scanner uses internal the same input/stream (probably due to the buffering) which the first Scanner object already has consumed ?!
I would advise you to use only one scanner object and close this scanner once at the end!

package temp;

import java.util.Scanner;

public class Temp {

	private static Scanner input = new Scanner(System.in);
	
	public static void main(String[] args) {
		char type = ' ';
		double userTemp = 0;
		double convertedTemp = 0;

		type = GetTempType();
		userTemp = GetTemp(type);
		
		input.close();

		switch (type) {
		case 'F':
			convertedTemp = ConvertCtoF(userTemp);
			break;
		case 'C':
			convertedTemp = ConvertFtoC(userTemp);
			break;
		}

		DisplayResults(convertedTemp, type);

	}// End main

	// Parameters: double - temp
	// char - temp type
	// Returns: void
	private static void DisplayResults(double temp, char type) {

		if (type == 'F') {
			System.out.println("The temperature in Farenheit: " + temp);
		} else if (type == 'C') {
			System.out.println("The temerature in Celcius: " + temp);
		}
	}// ENd DisplayResults

	// Parameters: double - Farenheit temp
	// Returns: double - Celcius temp
	private static double ConvertCtoF(double tempC) {
		double tempF = tempC * 1.8 + 32;
		return tempF;
	}// end ConvertCtoF

	// Parameters: double - Celsius temp
	// Returns: double - Farenheit temp
	private static double ConvertFtoC(double tempF) {
		double tempC = (tempF - 32) / 1.8;
		return tempC;
	}// end ConvertFtoC

	// Parameters: char - F or C (For types of temps)
	// Returns: double - Entered Temp
	private synchronized static double GetTemp(char type) {
		double temp = 0;


		if (type == 'C') {
			System.out.print("Please enter the temperature in Fahrenheit: ");
			temp = input.nextDouble();
		} else if (type == 'F') {
			System.out.print("Please enter the temperature in Celcius: ");
			temp = input.nextDouble();
		}

		return temp;
	}// End GetTemp

	// prompts and reads a char from user, then returns a cleaned version
	private synchronized static char GetTempType() {
		char type = ' ';
		boolean notSet = true;


		while (notSet) {
			System.out
					.print("Would you like to convers to (C)elsius to (F)ahrenheit?");
			type = input.next().charAt(0);

			if (type == 'C' || type == 'c') {
				type = 'C';
				notSet = false;
			} else if (type == 'F' || type == 'f') {
				type = 'F';
				notSet = false;
			} else {
				System.out.println("Not a valid entry.");
			}
		}// End While loop
	

		return type;
	}// end GetTempType

}

info - getTemp method:
if(type == 'C'){
System.out.print("Please enter the temperature in Fahrenheit: ");

are you sure that this is correct? :)

and please take a look at the Java Code/naming Conventions

[OmegaNine]

The way its worded is kind of funny, but to the user it is fine. If they are choosing C they are wanting to convert to C from F. Its still being put together, I ran in this problem and the teacher had no idea what was wrong. I rewrote the program last night and still got the same error so I cam here.

Thanks for the naming cheat sheet. Its been forever since I took a java class. This is actually a LAN class, but he gave me these assignments as a "refresher" for our final project.

It looks like moving it to a class scope works perfectly. Thank you for your help, I will be sure to tell my teacher where I got the help ;)