Code

/// Name: Dylan Sleeper
/// Period: 6
/// Program Name: Flip Probability
/// File Name: flipProbability.java
/// Date Finished: 1/22/2016

import java.util.Scanner;
import java.util.Random;

public class flipProbability{

    public static void main(String[] args){
        
        Random r = new Random();
        Scanner keyboard = new Scanner(System.in);
        
        double tailsCount = 0;
        double headsCount = 0;
        
        int userInput;
        int times = 0;
        
        System.out.println("How many times would you like to flip the coin?");
        do{
            userInput = 0;
            if(times > 0){
                System.out.println("Not a valid number. Please enter another number.");
            }
            System.out.print("> ");
            String temp = keyboard.next();
            
            // The try and catch to make sure the number is a valid integer that isn't a string, double, or too big. This
            // prevents the program from crashing.
            
            try{
                userInput = Integer.parseInt(temp);
            }
            catch(java.lang.NumberFormatException e){
                userInput = -1;
            }
            
            times++;
            System.out.println("");
            // This checks to make sure the number isn't negative or 0 because that would throw errors later in the
            // program.
            
        } while(userInput <= 0);
        
        for(int i = 0; i < userInput; i++){
            
            int flip = r.nextInt(2);
            if(flip == 0){
                tailsCount++;
            }
            else{
                headsCount++;
            }
            
        }
        
        double total = userInput;
        double tailsPercent = (tailsCount / total) * 100;
        double headsPercent = (headsCount / total) * 100;
        
        System.out.println("Heads: " + headsPercent + "%");
        System.out.println("Tails: " + tailsPercent + "%");
        
        System.out.println("");
        
        System.out.println("You rolled " + headsCount + " heads and " + tailsCount + " tails.");
        
    }

}

/*
I found that using about 8000 gets consistently close to 50% every time.
*/

  

Outputs