Para completar (aunque se han dado varias respuestas buenas, Me gusta Mark's y Joachim's best), aquí hay dos versiones basadas en String.split(regex) y String.split(regex, limit):
(Edición, corrección de errores :)
boolean containsAtLeastTwoAsterisks = ("_" + myString + "_").split("\\*", 3).length == 3;
boolean containsExactlyTwoAsterisks = ("_" + myString + "_").split("\\*").length == 3;
me escribió a little benchmark basado en nuestras respuestas (lo sé, los puntos de referencia no significan mucho, pero son diversión, y el mío es probablemente una mierda, lo sé .) de todos modos, aquí están los resultados de un análisis de la muestra:
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Testing strings with one or less asterisk
Processor: bhups
Finished. Duration: 40 ms, errors: 0
Processor: Bozho (loop version)
Finished. Duration: 33 ms, errors: 0
Processor: Bozho (regex version)
Finished. Duration: 806 ms, errors: 0
Processor: Joachim Sauer
Finished. Duration: 24 ms, errors: 0 <-- winner
Processor: Mark Byers
Finished. Duration: 1068 ms, errors: 0
Processor: seanizer
Finished. Duration: 408 ms, errors: 0
*********************************************************************************
Testing strings with exactly two asterisks
Processor: bhups
Finished. Duration: 14 ms, errors: 0 <-- winner
Processor: Bozho (loop version)
Finished. Duration: 21 ms, errors: 0
Processor: Bozho (regex version)
Finished. Duration: 693 ms, errors: 0
Processor: Joachim Sauer
Finished. Duration: 14 ms, errors: 0 <-- winner
Processor: Mark Byers
Finished. Duration: 491 ms, errors: 0
Processor: seanizer
Finished. Duration: 340 ms, errors: 0
*********************************************************************************
Testing strings with more than two asterisks (not all processors will be included)
Skipping processor bhups
Processor: Bozho (loop version)
Finished. Duration: 63 ms, errors: 0 <-- winner
Skipping processor Bozho (regex version)
Skipping processor Joachim Sauer
Processor: Mark Byers
Finished. Duration: 1555 ms, errors: 0
Processor: seanizer
Finished. Duration: 860 ms, errors: 0
parece que no expresiones regulares es mucho más rápido que la expresión regular. Eso es lo que esperarías, supongo.
EDITAR: solucionó el ganador incorrecto. lo siento, joachim
Al menos dos o exactamente dos? –
Debe ser exactamente dos – Achaius