Monads/Maybe monad: Difference between revisions
→{{header|Java}}
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<syntaxhighlight>
import java.util.Optional;
/**
* Java has a built-in generic "Maybe" monad in form of the Optional<T> class.
*
* The class has static methods, "of" and "ofNullable", which act as the unit function
* for wrapping nullable and non-nullable values respectively.
* The class instance method, "flatMap", acts as the bind function. *
*/
public final class MonadMaybe {
public static void main(String[] aArgs) {
System.out.println(doubler(5).flatMap(MonadMaybe::stringify).get());
System.out.println(doubler(2).flatMap(MonadMaybe::stringifyNullable).get());
Optional<String> option = doubler(0).flatMap(MonadMaybe::stringifyNullable);
String result = option.isPresent() ? option.get() : "Result is Null";
System.out.println(result);
}
private static Optional<Integer> doubler(int aN) {
return Optional.of(2 * aN);
}
private static Optional<String> stringify(int aN) {
return Optional.of("A".repeat(aN));
}
private static Optional<String> stringifyNullable(int aN) {
return ( aN > 0 ) ? Optional.ofNullable("A".repeat(aN)) : Optional.ofNullable(null);
}
}
</syntaxhighlight>
{{ out }}
<pre>
AAAAAAAAAA
AAAA
Result is Null
</pre>
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