gistfile1.txt

Requirements:
1) Parse n properties from a Map
2) Fail fast with good error message if such a property is not the correct type (for example partCount is not an int)
3) Fail fast if an unknown key is in the Map
4) Do not modify the Map because it is reused

Proposal A:

    public void applyCustomProperties(Map<String, String> customPropertyMap) {
        String partCountString = customPropertyMap.remove("partCount"); // BUG: MODIFIES MAP
        try {
            partCount = partCountString == null ? 4 : Integer.parseInt(partCountString);
        } catch (NumberFormatException e) {
            throw new IllegalArgumentException("The partCount (" + partCountString + ") cannot be parsed.", e);
        }
        String minimumProcessListSizeString = customPropertyMap.remove("minimumProcessListSize");
        try {
            minimumProcessListSize = minimumProcessListSizeString == null ? 75 : Integer.parseInt(minimumProcessListSizeString);
        } catch (NumberFormatException e) {
            throw new IllegalArgumentException("The minimumProcessListSize (" + minimumProcessListSizeString + ") cannot be parsed.", e);
        }
        if (!customPropertyMap.isEmpty()) {
            throw new IllegalStateException("The customProperties (" + customPropertyMap.keySet()
                    + ") are not supported.");
        }
    }

Proposal B:

    public void applyCustomProperties(Map<String, String> customPropertyMap) {
        partCount = 4;
        minimumProcessListSize = 25;
        customPropertyMap.forEach((key, value) -> {
            switch (key) {
                case "partCount":
                    try {
                        partCount = Integer.parseInt(value);
                    } catch (NumberFormatException e) {
                        throw new IllegalArgumentException("The partCount (" + value + ") cannot be parsed.", e);
                    }
                    break;
                case "minimumProcessListSize":
                    try {
                        minimumProcessListSize = Integer.parseInt(value);
                    } catch (NumberFormatException e) {
                        throw new IllegalArgumentException("The minimumProcessListSize (" + value + ") cannot be parsed.", e);
                    }
                    break;
                default:
                    throw new IllegalArgumentException("The customProperty (" + key + ") with value (" + value
                            + ") is not supported.");
            }
        });
    }

8

int partCount = 8;

int partCount = 4; // DEFAULT

8

// => Exception

public void applyCustomProperties(Map<String, String> customPropertyMap) {
partCount = 4;
minimumProcessListSize = 25;
customPropertyMap.forEach((key, value) -> {
switch (key) {
case "partCount":
try {
partCount = Integer.parseInt(value);
} catch (NumberFormatException e) {
throw new IllegalArgumentException("The partCount (" + value + ") cannot be parsed.", e);
}
break;
case "minimumProcessListSize":
try {
minimumProcessListSize = Integer.parseInt(value);
} catch (NumberFormatException e) {
throw new IllegalArgumentException("The minimumProcessListSize (" + value + ") cannot be parsed.", e);
}
break;
default:
throw new IllegalArgumentException("The customProperty (" + key + ") with value (" + value
+ ") is not supported.");
}
});
}

validation monad

private int a;
private double b;

public void doRegisters(foo) {
a = foo.extract(("a", String value) -> Integer.parseInt(value), 4);
b = foo.extract(("b", String value) -> Double.parseDouble(value), 0.25);
foo.validateNoOtherKeys();
}

Map<String, Object>
"a" -> 4;
"b" -> 0.25;

Map<String, Function>
("a", value) -> Integer.parseInt(value);
("b", value) -> Double.parseDouble(value);

Map<String, String> customPropertyMap

private int a;
private double b;