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JavaCro'14 - JCalc Calculations in Java with open source API – Davor Sauer

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During different calculations with decimal numbers in Java we come to problem with using primitive data types and their precision. Especially when we work with a double and we come across of losing precision. Another solution is to use BigDecimal, but still we have a problem of easy writing formula. JCalc open source API provides easy writing formula in Java and maintaining precision offered by the BigDecimal. This talk will cover basic JCalc usage and functionalities of API.

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JavaCro'14 - JCalc Calculations in Java with open source API – Davor Sauer

  1. 1. Calculations in Java with open source APICalculations in Java with open source APICalculations in Java with open source APICalculations in Java with open source API Author: Davor Sauer www.jdice.org
  2. 2. Content Calculations in Java- basics Calculations in Java with JCalc Comparison of complex calculation with plain Java and Features Questions of complex calculation with plain Java and JCalc
  3. 3. Calculations in Java- Example: Simple calculation: If you pay $2.00 for a beer that costs $1.10, how much changes do you get? System.out.println(2.00 - 1.10); Answers: a) b) c) d) gDecimal payment = new BigDecimal(2.00); Answers:gDecimal payment = new BigDecimal(2.00); gDecimal cost = new BigDecimal(1.10); ystem.out.println(payment.subtract(cost)); Answers: a) b) c) d) => 0.89999999991118215802998747... gDecimal payment = new BigDecimal("2.00"); gDecimal cost = new BigDecimal("1.10"); ystem.out.println(payment.subtract(cost)); Answers: a) b) c) d) - basics Simple calculation: If you pay $2.00 for a beer that costs $1.10, Answers: .9 .90 0.899999999999 None of the above Answers:Answers: .9 .90 0.899999999999 None of the above => 0.89999999991118215802998747... Answers: .9 0.90 0.899999999999 None of the above
  4. 4. ava + JCalc ...more sugar?
  5. 5. Calculations in Java- Example: Simple calculation: If you pay $2.00 for a beer that costs $1.10, how much changes do you get? System.out.println(Calculator.builder().val(2.00).sub(1.10). m p = new Num(2.00); m c = new Num(1.10);m c = new Num(1.10); tem.out.println(Calculator.builder().val(p).sub(c).calculate m p = new Num("2.00"); m c = new Num("1.10"); tem.out.println(Calculator.builder().val(p).sub(c).setStripTrailingZeros tem.out.println(Calculator.builder("2.00 - 1.10").setStripTrailingZeros - basics Simple calculation: If you pay $2.00 for a beer that costs $1.10, ().val(2.00).sub(1.10).calculate()); Answers: a) 0.9 b) .90 c) 0.899999999999 d) None of the above 0.899999999999 d) None of the above calculate()); Answers: a) .9 b) .90 c) 0.899999999999 d) None of the above setStripTrailingZeros(false).calculate()); setStripTrailingZeros(false).calculate()); Answers: a) .9 b) 0.90 c) 0.89999999 d) None of th 0.9 0.89999999991118215802998747...
  6. 6. Complex example Calculate fixed monthly payment for a fixed rate mortgage by Java ecimal interestRate = new BigDecimal("6.5"); // fixed yearly interest rate in % ecimal P = new BigDecimal(200000); ecimal paymentYears = new BigDecimal(30); onthly interest rate => 6.5 / 12 / 100 = 0.0054166667 ecimal r = interestRate.divide(new BigDecimal(12), 10, BigDecimal.ROUND_HALF_UP).divide(new umerator > 0.005416666 * 200000 = 1083.3333400000 ecimal numerator = r.multiply(P); enominatorenominator .add(new BigDecimal(1)); // => 1.0054166667 ecimal pow = new BigDecimal(30 * 12); // N = 30 * 12 > 1.005416666 ^ (-30 * 12) ===> 1 / 1.005416666 ^ (30 * 12) ecimal one = BigDecimal.ONE; ecimal r_pow = r.pow(pow.intValue()); // => 1.0054166667 ^ 360 = 6.99179805731691416804.... w = one.divide(r_pow, 10, BigDecimal.ROUND_HALF_UP); // => 1 / 6.991798.. = 0.1430247258 > 1 - 0.1430247258 = 0.8569752742 ecimal denominator = new BigDecimal(1); minator = denominator.subtract(r_pow); > 1083.3333400000 / 0.8569752742 = 1264.1360522464 ecimal c = numerator.divide(denominator, 10, BigDecimal.ROUND_HALF_UP); .setScale(2, BigDecimal.ROUND_HALF_UP); em.out.println("c = " + c); Calculate fixed monthly payment for a fixed rate mortgage by Java ).divide(new BigDecimal(100), 10, BigDecimal.ROUND_HALF_UP); // => 1.0054166667 ^ 360 = 6.99179805731691416804.... // => 1 / 6.991798.. = 0.1430247258 Line of code: 15
  7. 7. Complex example Calculate fixed monthly payment for a fixed rate mortgage by Java m interestRate = new Num(6.5); // fixed yearly interest rate in % m P = new Num(200000); m paymentYears = new Num(30); monthly interest rate : r = 6.5 / 100 / 12 m r = Calculator.builder().openBracket().val(interestRate).div(100).closeBracket().div(12).calculate(); = 30 * 12 * -1 m N = Calculator.builder().val(paymentYears).mul(12).mul(-1).calculate(); = (r * P) / (1 / (1 + r)^N ulator c = new Calculator() = (r * P) / (1 / (1 + r)^N ulator c = new Calculator() .openBracket() .val(r).mul(P) .closeBracket() // numerator .div() // --------------- .openBracket() // denumerator .val(1).sub().openBracket().val(1).add(r).closeBracket .closeBracket(); m result = c.calculate().setScale(2); em.out.println("c = " + result); Line Calculate fixed monthly payment for a fixed rate mortgage by Java ().div(12).calculate(); closeBracket().pow(N) Line of code: 8
  8. 8. Complex example Calculate fixed monthly payment for a fixed rate mortgage by Java m interestRate = new Num("A", 6.5); m P = new Num("B", 200000); m paymentYears = new Num("C", -30); ulator c = Calculator.builder("((A / 100 / 12) * B) / (1 - ((1 + (A / 100 / 12)) ^ (C * 12)))", m result = c.calculate(); em.out.println("c = " + result.setScale(2)); Line Calculate fixed monthly payment for a fixed rate mortgage by Java ((1 + (A / 100 / 12)) ^ (C * 12)))", interestRate, P, paymentYears); Line of code: 6
  9. 9. Feature: Show calculation Num interestRate = new Num("A", 6.5); Num P = new Num("B", 200000); Num paymentYears = new Num("C", -30); Calculator c = Calculator.builder("((A / 100 / 12) * B) / (1 - ((1 + (A / 100 / 12)) ^ (C * 12)))", c.setScale(10); Num result = c.calculate(true, false); // track calculation steps, track details for(String step : c.getCalculationSteps()) System.out.println(step); System.out.println("c = " + result.setScale(2)); Output: 6.5 / 100 = 0.065 0.065/ 12 = 0.0054166667 0.0054166667 * 200000 6.5 / 100 = 0.065 0.065/ 12 = 0.0054166667 1 + 0.0054166667 -30 * 12 = -360 1.0054166667 ^ -360 1 - 0.1430247258 1083.33334/ 0.8569752742 c = 1264.14 calculation steps ((1 + (A / 100 / 12)) ^ (C * 12)))", interestRate, P, paymentYears); = 0.065 = 0.0054166667 * 200000 = 1083.33334 = 0.065 = 0.0054166667 + 0.0054166667 = 1.0054166667 360 = 0.1430247258 = 0.8569752742 / 0.8569752742 = 1264.1360522464
  10. 10. Feature: Modularity Calculator calc = new Calculator(); calc.register(QuestionOperator.class); // register custom operator '?' calc.register(SumFunction.class); // register custom function 'sum' calc.expression("2 ? 2 + 5 - 1 + sum(1,2,3,4)"); @SingletonComponent@SingletonComponent public class QuestionOperator implements Operator { .... // module for ‘?’ operator .... } @SingletonComponent public class SumFunction implements Function { .... // module for function ‘sum’ .... } // register custom operator '?' register custom function 'sum' implements Operator {
  11. 11. Feature: Default configuration roundingMode=HALF_UP scale=2 stripTrailingZeros=true decimalSeparator.out='.' decimalSeparator.in='.' numconverter[0]=org.jdice.calc.test.NumTest$CustomObject > org.jdice.calc.test.NumTest$CustomObjectNumConverter Configure default properties with 'jcalc.properties' file in class path numconverter[0]=org.jdice.calc.test.NumTest$CustomObject > org.jdice.calc.test.NumTest$CustomObjectNumConverter operator[0]=org.jdice.calc.test.CustomOperatorFunctionTest$QuestionOperator function[0]=org.jdice.calc.test.CustomOperatorFunctionTest$SumFunction configuration org.jdice.calc.test.NumTest$CustomObjectNumConverter ' file in class path org.jdice.calc.test.NumTest$CustomObjectNumConverter org.jdice.calc.test.CustomOperatorFunctionTest$QuestionOperator org.jdice.calc.test.CustomOperatorFunctionTest$SumFunction
  12. 12. ions, ideas, suggestions… Project page: www.jdice.org

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