Android Open Source - bin.calc_android Basic Arith Operator

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License

The source code is released under:

GNU General Public License

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Java Source Code

package info.ohgita.android.bincalc.calculator;
//w  ww .  j a v a  2s  .c o  m
import java.math.BigDecimal;
import java.util.Iterator;
import java.util.LinkedList;

import android.util.Log;

/**
 * Basic arithmetic operator class
 * 
 * Basic arithmetic operation from LinkedList (Parsed decimal numerical formula).
 * 
 * @author Masanori Ohgita
 * 
 */
public class BasicArithOperator {
  protected LinkedList<String> list;
  protected int roundingScale;
  
  /**
   * Constructor
   * @param round_scale Rounding scale
   */
  public BasicArithOperator(int round_scale) {
    roundingScale = round_scale;
  }
  
  public BasicArithOperator() {
    roundingScale = 2; // second digit
  }
  
  /**
   * Calculate a numerical formula
   * @param linkedList LinkedList (Parsed numerical formula)
   * @return Calculated result
   */
  public String calculate(LinkedList<String> linkedList){
    list = linkedList;
    Log.i("BasicArithOperator","calculation(...) "+list.toString());
    return eval(list.iterator());
  }
  
  /**
   * eval (recursive method)
   * @param iter LinkedList iterator
   * @return resultant value String
   */
  protected String eval(Iterator<String> iter){
    Log.i("BasicArithOperator", " eval(...)");
    BigDecimal result = new BigDecimal(0);
    String beforeStr = "";
    while(iter.hasNext()){
      String str = iter.next();
      Log.i("BasicArithOperator","  * str: "+str + " - result = "+result);
      if(str.contentEquals("(")){
        Iterator<String> it = iter;
        str = eval(it);
      }else if(str.contentEquals(")")){
        Log.i("BasicArithOperator","  * break");
        break;
      }
      
      if(beforeStr.contentEquals("+")){
        Log.i("BasicArithOperator","    * "+result+" += "+str);
        result = result.add(new BigDecimal(str));
      }else if(beforeStr.contentEquals("-")){
        Log.i("BasicArithOperator","    * "+result+" -= "+str);
        result = result.subtract(new BigDecimal(str));
      }else if(beforeStr.contentEquals("*")){
        Log.i("BasicArithOperator","    * "+result+" *= "+str);
        result = result.multiply(new BigDecimal(str));
      }else if(beforeStr.contentEquals("/")){
        Log.i("BasicArithOperator","    * "+result+" /= "+str);
        BigDecimal bd = new BigDecimal(str);
        result = result.divide(bd, roundingScale, BigDecimal.ROUND_HALF_UP);
      }else if(beforeStr.length() == 0){
        Log.i("BasicArithOperator","    * "+result+" = "+str);
        result = new BigDecimal(str);
      }
      iter.remove();
      beforeStr = str;
    }
    Log.i("BasicArithOperator", " * return("+result+")");
    return result.toString();
  }
}

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