Android5.0 Calculator calculation results inaccurate and redundant ' 0 ' at the end of the result does not omit the workaround

The Android5.0 calculator calculates inaccurate results and the excess ' 0 ' at the end of the result is not omitted

First, the description of the problem:

"Test Steps"

1. Enter the calculator

2. Enter 100-99.9

3. View Calculation results

"Test Results"

1. The result is: 0.0999999999

"Expected results"

1. The result should be: 0.1

"Test Steps"

1. Enter the calculator

2. Enter 1000-999.9 to see if the result is: 0.1

"Test Results"

1. The result is shown as: 0.10000000

"Expected results"

1. Calculation results The extra 0 after the decimal point should be omitted.

Second, the solution: path:

<span style= "FONT-SIZE:18PX;" >package Com.android.calculator2; <span style= "color: #ff0000;" >import java.util.locale;//added </span>import Org.javia.arity.symbols;import Org.javia.arity.syntaxexception;import Org.javia.arity.Util;    public class Calculatorexpressionevaluator {private static final int max_digits = 12;     private static final int rounding_digits = 2;    Private final Symbols Msymbols;     Private final Calculatorexpressiontokenizer Mtokenizer; <span style= "color: #ff0000;" >private static final String nan = "nan";//added</span> public calculatorexpressionevaluator (Calculatorex        Pressiontokenizer tokenizer) {msymbols = new Symbols ();    Mtokenizer = Tokenizer;    } public void evaluate (Charsequence expr, Evaluatecallback callback) {Evaluate (expr.tostring (), callback); } public void evaluate (String expr, Evaluatecallback callback) {expr = Mtokenizer.getnormalizedexpression (exp         R); Remove any trailing operators while (Expr.length () > 0 && "+-/*". IndexOf (Expr.charat (Expr.length ()-1))! =        -1) {expr = expr.substring (0, Expr.length ()-1); } try {if (expr.length () = = 0 | |                double.valueof (expr) = null) {callback.onevaluate (expr, null, calculator.invalid_res_id);            Return }} catch (NumberFormatException e) {//expr is not a simple number} try {D            ouble result = Msymbols.eval (expr);            if (Double.isnan (Result)) {callback.onevaluate (expr, null, R.string.error_nan);                } else {//the arity library uses floating point arithmetic when evaluating the expression leading to precision errors in the result. The method doubletostring hides these//errors;            Rounding the result by dropping N digits of precision. <span style= "color: #ff0000;" >/*add*/String strresult = ""; for (int precision = max_digits; precision > 6; precision--) {strresult = Tryformattingwithprecision (re                    Sult, precision);                    if (Strresult.length () <= max_digits) {break; }}/*end*/</span> <span style= "color: #ff0000;" > Final String resultstring = mtokenizer.getlocalizedexpression (/*util.doubletostring (result, Max_digits, Rounding_digits) */strresult);//modified</span> callback.onevaluate (expr, resultString, Ca Lculator.            INVALID_RES_ID);        }} catch (Syntaxexception e) {callback.onevaluate (expr, null, r.string.error_syntax); }} public interface Evaluatecallback {public void onevaluate (string expr, string result, int errorresource    ID); }</span>

<span style= "FONT-SIZE:18PX;" ><span style= "color: #ff0000;" >/*added*/Private String tryformattingwithprecision (double value, int precision) {//the standard Scie Ntific Formatter is basically what we need.        We'll/start with what it produces and then massage it a bit.        String result = String.Format (locale.us, "%" + max_digits + "." + precision + "G", value);        if (Result.equals (NAN)) {//Treat Nan as Error return "Nan";        } String mantissa = result;        String exponent = null;        int e = result.indexof (' e ');             if (E! =-1) {mantissa = result.substring (0, E);            Strip "+" and unnecessary 0 ' s from the exponent exponent = result.substring (e + 1);            if (Exponent.startswith ("+")) {exponent = exponent.substring (1);        } exponent = string.valueof (Integer.parseint (exponent));     } else {mantissa = result;   } int period = Mantissa.indexof ('. ');        if (period = =-1) {period = Mantissa.indexof (', '); } if (Period! =-1) {//Strip trailing 0 ' s while (Mantissa.length () > 0 && Mantis            Sa.endswith ("0")) {mantissa = mantissa.substring (0, Mantissa.length ()-1); } if (mantissa.length () = = period + 1) {mantissa = mantissa.substring (0, Mantissa.length ()-1)            ;        }} if (exponent! = null) {result = Mantissa + ' e ' + exponent;        } else {result = Mantissa;    } return result; }/*end*/</span>}</span>

Android5.0 Calculator calculation results inaccurate and redundant ' 0 ' at the end of the result does not omit the workaround