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Clash Royale CLAN TAG

Add null-like value to String in Java

I am writing test method like setTask(Task task). And Task object has several fields, e.g.

setTask(Task task)

Task

public String vehicle;


Method setTask should be used in different test-cases, so I'd like to have an options for this field to accept values:

setTask

null

some string value

"", "Hello, World!", "Iso Isetta", ...

random

So what can I do to make String to be SpecialString which could accept values null, random & some string value? (BTW: I don't want to set it to string value "RANDOM", and chech whether the value is equal to "RANDOM"-string)

String

SpecialString

null

random

some string value

UPDATE: I don't mean random like random value from a set of values, I mean random as well as null and this is for setTask() to handle random (select random from drop-down), and not to pass a random string from a set of values.

random

random value from a set of values

random

null

setTask()

random

1 Answer
1

Don't assign a fixed String but use a Supplier<String> which can generate a String dynamically:

String

Supplier<String>

String

public Supplier<String> vehicleSupplier;


This, you can assign a generator function as you request:

static Supplier<String> nullSupplier () { return () -> null; }
static Supplier<String> fixedValueSupplier (String value) { return () -> value; }
static Supplier<String> randomSupplier (String... values) {
int index = ThreadLocalRandom.current().nextInt(values.length) -1;
return index > 0 && index < values.length ? values[index] : null;
}


In use, this looks like:

task.setVehicleSupplier(nullSupplier()); // or
task.setVehicleSupplier(fixedValueSupplier("value")); // or
task.setVehicleSupplier(randomSupplier("", "Hello, World!", "Iso Isetta"));


and you can get the String by

String value = task.vehicleSupplier().get();


or hide the implementation in a getter function

class Task {
// ...
private Supplier<String> vehicleSupplier;
public void setVehicleSupplier(Supplier<String> s) {
vehicleSupplier = s;
}
public String getVehicle() {
return vehicleSupplier != null ? vehicleSupplier.get() : null;
}
// ...
}


random

random value from a set of values

random

null

setTask()

random

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