Chemical Forumlae

Question

Hi....I was wondering if any-one could help me with this problem I'm having.
Basically what I'm trying to do is create a program that allows the user to enter a chemical forumulae such as CaCO3
and the output to that should be, C is the symbol for Carbon and there is 1 atom of this element, Ca for Calcium (1 atom),
O for Oxygen (3 atoms)
There is a text file with all the elements in it.
eg of text file:
Ag Silver
Al Aluminium
Au Gold
C Carbon
Ca Calcium
etc...
Below I've created a program that doesn't use a file to read the data from, I put some of the contents of the file in
a string. ((I have to change this later))
Anyway, I need to use an IDE to run the program...through some help from some java tutorials, I've created a program that
almost works. However, I made the program so It has to have 'arguments'.
IE... if I type in; java ChemicalFormulae CaCO3 ((In DOS MODE)) brings out the right result.
and if I also click on the run tab, then click on 'arguments' and type in 'H2O', it would bring out the right result.
You see...the program needs parametres to run successfully...
import java.util.regex.*;
public class ChemicalFormulae {
/* names should be loaded dynamically from that file */
private String[] names = {"H", "C", "Ca", "O"};
private Matcher matcher = null;
private Pattern pattern = null;
static java.io.PrintStream p = System.out;
public static void main(String[] args) {
ChemicalFormulae inoh = new ChemicalFormulae();
for (int i = 0; i < args.length; i++) {
if (inoh.isValid(args[ i])) {
inoh.check(args[ i]);
} else {
System.out.println("Illegal formula: " + args[ i]);
public ChemicalFormulae() {
String regex = "([A-Z][a-z]?+)([0-9]*+)";
pattern = Pattern.compile(regex);
matcher = pattern.matcher("");
/* Element name needs real solution, current implementation is too static ;) */
private String getElementName(String s) {
if ("H".equals(s)) {
return "Hydrogen";
} else if ("O".equals(s)) {
return "Oxygen";
} else {
return s;
private String getElementCount(String s) {
if ("".equals(s)) {
return "1";
} else {
return s;
private static void order() {
p.println("Would you like fries with that?");
public boolean isValid(String formula) {
String regex = "((";
for (int i = 0; i < names.length; i++) {
regex += (i == 0 ? "(" : "|(") + names[ i] + ")";
regex += "){1}[0-9]*)+";
return formula.matches(regex);
/* check needs better name and should be redesigned to just collect data */
public void check(String formula) {
int end = 0;
matcher = matcher.reset(formula);
while (matcher.find(end)) {
end = matcher.end();
System.out.println("Element " + getElementName(matcher.group(1))
+ " occured " + getElementCount(matcher.group(2)) + " time(s)");
}

Answer 1

I later created this program, so the user has a GUI interface and can type in the parametres in the text box.
However, I later found out that whatever I tried, the user cannot type in parametres at run-time mode.
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.regex.*;
public class ChemicalF
JFrame userInputGUI;          //frame to take some input from user
JLabel userPrompt;          //display prompt
JTextField userInput;     //for entry of text
JTextField echoBack;          //display back to user
JButton endProgram;          //ends program
String userChemical;          //stores the chemical entered
//ButtonListener buttonListen;          //listen for button press
/* names should be loaded dynamically from that file */
private String[] names = {"H", "C", "Ca", "O"};
private Matcher matcher = null;
private Pattern pattern = null;
static java.io.PrintStream p = System.out;
public static void main(String[] args) {
ChemicalF inoh = new ChemicalF();
for (int i = 0; i < args.length; i++) {
if (inoh.isValid(args[ i])) {
inoh.check(args[ i]);
} else {
System.out.println("Illegal formula: " + args[ i]);
public ChemicalF()
userInputGUI = new JFrame();          //create a window
userInputGUI.setTitle("Simple Demo of Swing JFrame");          //give window a title
userInputGUI.setBounds(100,100,500,300);          //set its size
Container cPane = userInputGUI.getContentPane();          //can only operate on content Pane
cPane.setLayout(null);          //suppress layout features
userPrompt = new JLabel("Enter a Chemical Formulae");          //add a label
userPrompt.setBounds(50,60,200,30);          //size and position it
cPane.add(userPrompt);          //add a label to content pane
userInput = new JTextField();          //text field to enter input
userInput.setBounds(250,60,100,30);          //size and position it
cPane.add(userInput);          //add a label to content pane
echoBack = new JTextField();          //echo back entered text
echoBack.setEditable(false);          //user can't alter
echoBack.setBounds(100,130,300,110);
cPane.add(echoBack);
endProgram = new JButton ("End");
endProgram.setBounds(300,100,100,30);
cPane.add(endProgram);
userInputGUI.setVisible(true);          //make window visible
userInput.addActionListener(new TextEventListener());          //to listen for event
class TextEventListener implements ActionListener          //nb inner class
               public void actionPerformed(ActionEvent eve)
if (eve.getSource()==userInput)          //was cursor in userInput when enter pressed
userChemical = userInput.getText();
System.out.print("user inputed " + userChemical); //puts whatever the user enters into the String called userChemical
echoBack.setText(userChemical);          //transfer to echo back
if (eve.getSource()==endProgram)
System.exit(0);
// public static void main(String[]args)     //main method
String regex = "([A-Z][a-z]?+)([0-9]*+)";
pattern = Pattern.compile(regex);
matcher = pattern.matcher("");
/* Element name needs real solution, current implementation is too static ;) */
private String getElementName(String s) {
if ("H".equals(s)) {
return "Hydrogen";
} else if ("O".equals(s)) {
return "Oxygen";
} else {
return s;
private String getElementCount(String s) {
if ("".equals(s)) {
return "1";
} else {
return s;
public boolean isValid(String formula) {
String regex = "((";
for (int i = 0; i < names.length; i++) {
regex += (i == 0 ? "(" : "|(") + names[ i] + ")";
regex += "){1}[0-9]*)+";
return formula.matches(regex);
/* check needs better name and should be redesigned to just collect data */
public void check(String formula) {
int end = 0;
matcher = matcher.reset(formula);
while (matcher.find(end)) {
end = matcher.end();
System.out.println("Element " + getElementName(matcher.group(1))
+ " occured " + getElementCount(matcher.group(2)) + " time(s)");
}