Input Mismatch error in java

Question

I am doing an AP CS Assignment and one of the instructions wanted me to read each column of data in my text file into 1 separate one dimensional arrays. I haven't been able to figure it out so far and could use some advice/help. When I try to run the program I also get the error "java.util.InputMismatchException null (in java.util.Scanner)

1980 Aug    945 100 Allen
1983 Aug    962 100 Alicia
1984 Sep    949 100 Diana
1985 Jul    1002    65  Bob
1985 Aug    987 80  Danny
1985 Sep    959 100 Elena

above is the text file and below is the code I am currently using.

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

public class Hurricanes2
{
    public static void main(String[] args)throws IOException
    {
        //declare and initialize variables

        File fileName = new File("hurcdata2.txt");
        Scanner inFile = new Scanner(fileName);
        int arrayLength = 59;
        int [] year = new int[arrayLength];
        String [] month = new String[arrayLength];
        int [] pressure = new int[arrayLength];
        int [] windSpeed = new int[arrayLength];



        //INPUT  - read data in from the file
        int n = 0;
        while (inFile.hasNext())
        {
            year[n] = inFile.nextInt();
            month[n] = inFile.next();
            pressure[n] = inFile.nextInt();
            windSpeed[n] = inFile.nextInt();
            System.out.println (year[n] + "\n");
            n++;
        }
        inFile.close();

Answer 1

You have both a String and an int so, either always ask for a String (and parse it later to an int), or, if you know the formatation of your file, you could use it in your favor. In your example, you have an int, String, int, int, String , and then a line break.

From here you could things in several ways.

One solution implies the use of a Scanner to read an entire line, and then using the String's method .split(String regex ), we create an array of Strings that we can now parse. However, for the method to work correctly, you need to be consistent in the way you separate your text. In my example, I used tab. I used your examples and tabbed them all. I won't show here because the editor won't conserve the tabs.

File fileName = new File("hurcdata2.txt");

int arrayLength = 6; //I used 6 since you showed 6 lines
//You could use an ArrayList or an algorithm to dynamically 
//increase the size of the arrays.
int [] year = new int[arrayLength];
String [] month = new String[arrayLength];
int [] pressure = new int[arrayLength];
int [] windSpeed = new int[arrayLength];

Scanner fileScanner = null;
try {
    fileScanner = new Scanner( fileName );
}
catch ( FileNotFoundException ex ) {
    //Exception handling;
}


int n = 0;
while( fileScanner.hasNext() ) {
    String toParse = fileScanner.nextLine();
    String[] splitedString = toParse.split( "\t" );

    year[n] = Integer.parseInt( splitedString[0] );
    month[n] = splitedString[1];
    pressure[n] = Integer.parseInt( splitedString[2] );
    windSpeed[n] = Integer.parseInt( splitedString[3] );
    n++;
}
fileScanner.close();

//I will include my test to check it.
for ( int i = 0 ; i < arrayLength; i++ ) {
    System.out.print( "\ni: " + i );
    System.out.print( " - year: " + year[i] );
    System.out.print( "; month: " + month[i] );
    System.out.print( "; pressure: " + pressure[i] );
    System.out.println( "; windSpeed: " + windSpeed[i] );
}

Another solution is to use a StringReader instead of .split( String regex );. StringReader is like a Scanner, but it is specialized in Strings.

You could also use a FileReader wrapped in a BufferedReader to read from the file.

FileReader myFileReader = null;
BufferedReader myBufferedReader = null;

try {
    myFileReader = new FileReader( fileName );
    myBufferedReader = new BufferedReader( myFileReader );

    int n = 0;
    String toParse = null;
    while( (toParse = myBufferedReader.readLine()) != null ) {
        //Is this confusing for you? ^
        String[] splitedString = toParse.split( "\t" );

        year[n] = Integer.parseInt( splitedString[0] );
        month[n] = splitedString[1];
        pressure[n] = Integer.parseInt( splitedString[2] );
        windSpeed[n] = Integer.parseInt( splitedString[3] );
        n++;
    }

}
catch ( FileNotFoundException ex ) {
    //Exception handling;
}
catch ( IOException ex ) {
    //Exception handling;
}
finally {
    try {
        myFileReader.close();
    }
    catch ( IOException ex ) {
        //Exception handling;
    }

    try {
        myBufferedReader.close();
    }
    catch ( IOException ex ) {
        //Exception handling;
    }        
}

I hope I have helped.

Have a nice day. :)

Answer 2

Each line of your file has 5 items in it, but your code only reads the first 4. So when it thinks it is starting the next line, it is actually trying to read the last item of the current line, which is not an int.

One solution would be to read the 5th item of each line, even if you don't have any where it needs to be stored.

Answer 3

Your are not picking the last column in the while loop. So at second loop, scanner try to read the 5th column as an int. You must add inFile.next() at the end of the while loop even if you don't use the result, so the scanner is not shifted at next loop.

Answer 4

Take a look at the input data

1980 Aug    945 100 Allen
1983 Aug    962 100 Alicia
1984 Sep    949 100 Diana

And what you're grabbing:

        while (inFile.hasNext())
        {
            year[n] = inFile.nextInt();
            month[n] = inFile.next();
            pressure[n] = inFile.nextInt();
            windSpeed[n] = inFile.nextInt();
            System.out.println (year[n] + "\n");
            n++;
        }

There are 5 fields in the input, and you're only grabbing 4. When it loops through for the second time, it expects to grab year(int) and instead grabs name(string).