CODEWITHSUNDEEP
java
W --
W --

Reputation: 314

How do I get the last 2 characters of a string and turn it into an int?

I'm 14 so we're learning about scientific equations and ions in school. Keep in mind I am very new to java and got the map thing from googling. I am also new to scientific equations hehe, so if you see anything please point it out (Although that is not part of the main question). I need practice in both areas so why not create a java program about science? ;) Anyway, I've got to the stage where I need to get the last 2 items in the String and change them to an integer and then I think I need to do algebra in java to solve a little equation for getting the little number infront of the letters. That's all I need to do then I can carry on making my program :D. Any help is very much appreciated and if you see anything else please point it out. Thanks!

This is the file: Run.java

package scientificFormula;

public class Run {

    public static void main(String[] args) {
        Formula formula = new Formula();

        formula.compound1 = args[0];
        formula.compound2 = args[1];

        String theFormula = formula.createFormula();
        System.out.println("Compound: " + args[0] + " " + args[1]
                + " = " + theFormula);
    }

}

and Formula.java:

package scientificFormula;

import java.util.HashMap;
import java.util.Map;

public class Formula {
    String compound1;
    String compound2;
    static private Map<String, String> map = new HashMap<String, String>();

    void initiateIons() {
        //1+
        map.put("Hydrogen", "H^1+");
        map.put("Lithium", "Li^1+");
        map.put("Sodium", "Na^1+");
        map.put("Potassium", "K^1+");
        map.put("Rubidium", "Rb^1+");
        //2+
        map.put("Magnesium", "Mg^2+");
        map.put("Calcium", "Ca^2+");
        map.put("Strontium", "Sr^2+");
        //3+
        map.put("Aluminium", "Al^3+");
        //3-
        map.put("Nitrogem", "N^-3");
        map.put("Phosphorus", "P^-3");
        //2-
        map.put("Oxygen", "O^-2");
        map.put("Sulfar", "S^-2");
        map.put("Selenium", "Se^-2");
        //1-
        map.put("Fluorine", "F^-1");
        map.put("Chlorine", "Cl^-1");
        map.put("Bromine", "Br^-1");
        map.put("Iodine", "I^-1");
    }

    String createFormula() {
        initiateIons();

        //Example Calcium Iodine:
        //2x + -1y = 0
        //x = 1 and y = 2

        String symbol1 = map.get(compound1);
        String symbol2 = map.get(compound2);

        return symbol1 + symbol2;
    }
}

edit:

In reply to the 2 comments below from Jigar and Eran: I went in properties and changed the arguments on Run.java...
input:

Sodium Chlorine

output:

Compound: Sodium Chlorine = Na^1+Cl^1-

for example this string: "Iodine", "I^-1" and the 2 items are -1 I want to make that int. Thanks.

Upvotes: 0

Views: 179

Answers (1)

carloabelli
carloabelli

Reputation: 4349

It sounds like you want the last two characters of the string not bits. If I'm not mistaken you want to grab the -2 at the end of something like Oxygen.

This can be done with these lines of code:

int i = Integer.parseInt(str.replace("+", "").substring(str.length() - 2));

The replace is necessary because parseInt does not like + in front of values only -.

Using Hot Licks suggestion of split you can do something like:

String[] symbol1Parts = symbol1.split("\\^");
int symbol1Int = Integer.parseInt(symbol1Parts[1].replace("+", "")); // the [1] assumes that there will only be one ^ character before the charge
String[] symbol2Parts = symbol2.split("\\^");
int symbol2Int = Integer.parseInt(symbol2Parts[1].replace("+", "")); // the [1] assumes that there will only be one ^ character before the charge

Upvotes: 4

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