File Checking Error, any ideas?

I am having troubles checking if the file is actually a file, then if not it's supposed to run through a loop asking for the user to re enter the filename, it says cannot find method exists()

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

public class Grades
{
public static void main ( String [] args ) throws IOException
{
int grade;
int kids = 0;
int max = 0;
int min = 100;
int passing = 0;
int a = 0;
int b = 0;
int c = 0;
int d = 0;
int f = 0;
int sum = 0;
int number;

String input2 = new String("input2");
Scanner input = new Scanner ( System.in );

System.out.println( "\n This program is designed to open a .txt file containing grades and display several statistics about the grades.");
System.out.println(" " );
System.out.println( "The availible input files, where you may input grades are:"
+ "\n\t Grades.txt"
+ "\n\t Grades2.txt"
+ "\n\t Grades3.txt"
+ "\n\t Grades4.txt"
+ "\n\t Grades5.txt");
System.out.print( "Please enter the filename that contains the grades you wish to use from the list above: ");
String file = input.nextLine();

File inputFile = new File(file);

while ( file.exists() == false )
{
System.out.println("\n File not found");
System.out.print("Please re-enter filename: ");
String file = input.nextLine();
}

Scanner con = new Scanner( inputFile );

while ( con.hasNext( ) )
{
number = con.nextInt( );
kids++;
sum = sum + number;
min = (number < min) ? number : min;

max = (number > max) ? number : max;

if ( number >= 60 )
passing++;

if ( number >= 90 )
a++;
else if ( (number < 90) && (number >= 80) )
b++;

else if ( (number < 80) && (number >= 70) )
c++;

else if ( (number < 70) && (number >= 60) )
d++;

else if ( number < 60 )
f++;
}

double average = sum / kids;

System.out.println( "The class information is as listed below:"
+ "\n\t Total Number of Kids: " + kids
+ "\n\t Average of All Grades: " + average
+ "\n\t Highest Grade: " + max
+ "\n\t Lowest Grade: " + min
+ "\n\t Number of Students who Passed: " + passing
+ "\n\t Number of Students who got an A: " + a
+ "\n\t Number of Students who got a B: " + b
+ "\n\t Number of Students who got a C: " + c
+ "\n\t Number of Students who got a D: " + d
+ "\n\t Number of Students who got an F: " + f );

}
}