Ytukyg

How would hashmap apply to this specific code, when an element can be anything within the periodic table if its from another source outside of the code.

public class element {

public static void main(String args)throws IOException{

    Scanner kbd = new Scanner(System.in);

    File file = new File("elements.txt");

    Scanner read = new Scanner(file);

    System.out.println("Enter a chemical compound: ");

    String compound = kbd.nextLine();

    compound = compound+" ";

    System.out.println("Chemical compound of "+compound);



    for (int x=0; x<compound.length();x++){

        if (compound.charAt(x)=='H'){

            String Hvalue = String.valueOf(compound.charAt(x+1));

            if (Character.isLetter(compound.charAt(x+1))) {

                Hvalue = String.valueOf(1);

            } else if (Character.isWhitespace(compound.charAt(x+1))){

                Hvalue = String.valueOf(1);

            }

            System.out.println(Hvalue+" part/s Hydrogen");

        } else if (compound.charAt(x)=='C'){

            String Cvalue = String.valueOf(compound.charAt(x+1));

            if (Character.isLetter(compound.charAt(x+1))) {

                Cvalue = String.valueOf(1);

            } else if (Character.isWhitespace(compound.charAt(x+1))){

                Cvalue = String.valueOf(1);

            }

            System.out.println(Cvalue+" part/s Carbon");

        } 

            } else if (Character.isWhitespace(compound.charAt(x+1))){

                Ovalue = String.valueOf(1);

            }

            System.out.println(Ovalue+" part/s Oxygen");

        }

    }



}

}

Assuming the format of the file will remain constant, below should work (based on JDK 8):

import java.io.File;

import java.io.IOException;

import java.util.Collections;

import java.util.HashMap;

import java.util.Map;

import java.util.Scanner;



public class Element {

    public static void main(String args) throws IOException {

        Scanner kbd = new Scanner(System.in);

        Map<String, Map<String, Double>> elementsMap = new HashMap<>();

        File file = new File("elements.txt");

        Scanner read = new Scanner(file);

        while (read.hasNext()) {

            elementsMap.putIfAbsent(read.next(), Collections.singletonMap(read.next(), Double.valueOf(read.next())));

        }





        System.out.println("Enter a chemical compound: ");

        String compound = kbd.nextLine();

        compound = compound + " ";

        System.out.println("Chemical compound of " + compound);



        double compoundWeight = 0.0;

        for (int x = 0; x < compound.length(); x++) {



            String elementKey = String.valueOf(compound.charAt(x));

            if (elementsMap.containsKey(elementKey)) {

                Map<String, Double> element = elementsMap.get(elementKey);

                int noOfElements = 0;



                while (String.valueOf(compound.charAt(x + 1)).matches("([1-9])")) {

                    noOfElements = ((noOfElements * 10) + Integer.parseInt(String.valueOf(compound.charAt(x + 1))));

                    x++;

                }



                noOfElements = noOfElements > 0 ? noOfElements : 1;



                System.out.println(noOfElements + " part/s " + element.keySet().iterator().next());

                compoundWeight += (element.values().iterator().next() * noOfElements);



            }

        }



        System.out.println("Atomic mass of " + compound + " is : " + compoundWeight);



    }

}