String Calculator

import java.util.Scanner;
import java.util.ArrayList;
/**
 * Calculates equations in the form of Strings
 *
 * @author Chris Koop
 * @version 1.0
 */
public class StringCalc
{
    public static void main(){
        Scanner inp =  new Scanner(System.in);
        String equation;
        double equals=0.0;
        System.out.println("Enter an equation using only +, -, *, and / as operators, and parenthesis for ordering");
        equation = inp.next();
        try{
            equals = Double.parseDouble(equation);
        }catch(java.lang.NumberFormatException e){
            System.out.println("Calculating");
            ArrayList<Integer> operloc = new ArrayList<Integer>();
            ArrayList<String> oper = new ArrayList<String>();
            ArrayList<Double> nums = new ArrayList<Double>();
            equParse(equation, oper, operloc, nums);
            equals=nums.get(0);
            parenCalc(oper, operloc, nums, equation);
            equals=nums.get(0);
        }
        System.out.println(equals);
    }
    private static void equParse(String equation, ArrayList<String> oper, ArrayList<Integer> operloc, ArrayList<Double> nums){
        for (int i=0; i<equation.length(); i++){
            if (equation.substring(i, i+1).equals("+")||equation.substring(i, i+1).equals("-")||equation.substring(i, i+1).equals("*")||equation.substring(i, i+1).equals("/")||equation.substring(i, i+1).equals("(")||equation.substring(i, i+1).equals(")")){
                operloc.add(i);
                oper.add(equation.substring(i,i+1));
                oper.trimToSize();
            }
        }
        nums.add(Double.parseDouble(equation.substring(0,operloc.get(0))));
        oper.trimToSize();
        if(oper.size()>1){
            for (int i=1; i<oper.size(); i++){
                if(equation.substring(operloc.get(i-1)+1,operloc.get(i)+1).equals("(")||equation.substring(operloc.get(i-1)+1,operloc.get(i)+1).equals(")")){
                    nums.add(Double.parseDouble(equation.substring(operloc.get(i)+1, operloc.get(i+1))));
                }else{
                    nums.add(Double.parseDouble(equation.substring(operloc.get(i-1)+1, operloc.get(i))));
                }
            }
        }
        if(equation.substring(operloc.get(oper.size()-1)).equals("(")||equation.substring(operloc.get(oper.size()-1)).equals(")")){
                    //nums.add(Double.parseDouble(equation.substring(operloc.get(oper.size()))));
                }else{
                    nums.add(Double.parseDouble(equation.substring(operloc.get(oper.size()-1))));
                }
    }
    private static void parenCalc(ArrayList<String> oper, ArrayList<Integer> operloc, ArrayList<Double> nums, String equation){
        int insertLoc=0;
        ArrayList<Integer> noperloc = new ArrayList<Integer>();
        ArrayList<String> noper = new ArrayList<String>();
        ArrayList<Double> nnums = new ArrayList<Double>();
        for (int i=0; i<equation.length()-1; i++){
            if (equation.substring(i, i+1).equals("(")){
                for (int j=equation.length()-1; j>i; i--){
                    if (equation.substring(j, j+1).equals(")")){
                        String newEqu=equation.substring(i,j);
                        int numOnums=0;
                        int numOops=0;
                        for (int k=0; k<equation.length(); k++){
                            if (equation.substring(k, k+1).equals("+")||equation.substring(k, k+1).equals("-")||equation.substring(k, k+1).equals("*")||equation.substring(k, k+1).equals("/")||equation.substring(k, k+1).equals("(")||equation.substring(k, k+1).equals(")")){
                                numOops++;
                            }
                        }
                        for (int k=0; k<equation.length(); k++){
                            if (equation.substring(k, k+1).equals("0")||equation.substring(k, k+1).equals("1")||equation.substring(k, k+1).equals("2")||equation.substring(k, k+1).equals("3")||equation.substring(k, k+1).equals("4")||equation.substring(k, k+1).equals("5")||equation.substring(k, k+1).equals("6")||equation.substring(k, k+1).equals("7")||equation.substring(k, k+1).equals("8")||equation.substring(k, k+1).equals("9")){
                                numOnums++;
                            }
                        }
                        for (int
                        insertLoc=i;
                        parenCalc(noper, noperloc, nnums, newEqu);
                        break;
                    }
                }
                calc(noper, nnums);
                nums.set(insertLoc,nnums.get(0));
            }
        }
        calc(oper, nums);
    }
    private static void calc(ArrayList<String> oper, ArrayList<Double> nums){
        for (int i=0; i<oper.size(); i++){
            if (oper.get(i).equals("*")){
                nums.set(i,nums.get(i)*nums.get(i+1));
                nums.remove(i+1);
                oper.remove(i);
                i--;
            }
        }
        for (int i=0; i<oper.size(); i++){
            if (oper.get(i).equals("/")){
                nums.set(i,nums.get(i)/nums.get(i+1));
                nums.remove(i+1);
                oper.remove(i);
                i--;
            }
        }
        for (int i=0; i<oper.size(); i++){
            if (oper.get(i).equals("+")){
                nums.set(i,nums.get(i)+nums.get(i+1));
                nums.remove(i+1);
                oper.remove(i);
                i--;
            }
        }
        for (int i=0; i<oper.size(); i++){
            if (oper.get(i).equals("-")){
                nums.set(i,nums.get(i)-nums.get(i+1));
                nums.remove(i+1);
                oper.remove(i);
                i--;
            }
        }
    }
}