Calculator Example

Let's build a calculator! Using the built-in BigInteger class we can easily construct a fluent api to access some of the math operations.

public static class Result extends AtomicReference<BigInteger> { }

Descriptor descriptor = Flapi.builder()
	.setDescriptorName("Calculator")
	.setPackage("unquietcode.tools.flapi.examples.calculator.builder")
	.setStartingMethodName("begin")

	.startBlock("Calculation", "$(int startingValue)").last()
		.addMethod("plus(int value)").any()
		.addMethod("minus(int value)").any()
		.addMethod("times(int value)").any()
		.addMethod("divide(int value)").any()
		.addMethod("power(int value)").any()
		.addMethod("mod(int value)").any()
		.addMethod("abs()").any()

		.addMethod("equals()").last(Result.class)
	.endBlock()
.build();

The usage is fairly straightforward, and looks something like this:

	Result _result = CalculatorGenerator.begin(new CalculatorHelperImpl())
		.$(0)
		.plus(1)
		.plus(1)
		.power(5)
		.divide(2)
	.equals();

	BigInteger result = _result.get();
	System.out.println(result);

If you were to include this builder in a project, you might want to wrap some of the messiness involved with instantiating a new builder. A user of the calculator should not have to instantiate the helper or remember the $(...) method to begin. Here I've introduced a Calculator class which wraps all this up.

static class Calculator {
    static CalculationBuilder<AtomicReference<BigInteger>> begin(int startingValue) {
        CalculatorBuilder.$ result = CalculatorGenerator.begin(new CalculatorHelperImpl());
        CalculationBuilder builder = result.$(startingValue);

        return builder;
    }
}

And now the usage is just a tiny bit cleaner:

    Result = result = 
    Calculator.begin(0)
        .plus(1)
        .plus(1)
        .power(5)
        .divide(2)
        .equals();

	System.out.println(result.get());

The full example can be found here.