Calculable result= new ExpressionBuilder(s1).build();
            size.setText(Double.toString(result.calculate()));
            size_num = result.calculate();

// ... snip ...

for (int i = 0; i < chars.length; i++) {

    // ... snip ...

    if (Character.isDigit(c)) {                                    // matches digit

        // ... snip ...

        while (chars.length > i + numberLen) {
            if (isDigitOrDecimalSeparator(chars[i + numberLen])) { // matches '.'

                // ... snip ...

s1 = s1.replace("t", "");
Calculable result= new ExpressionBuilder(s1).build();