Sometimes, when we don't know the value for given entry, we can use a default value. In Java, it would be done at entry adding:
public String getLetter(String key) { String letter = letters.get(key); return letter == null ? DEFAULT_LETTER : letter; }
Groovy does it at map definition time thanks to withDefault method:
@Test void "should assign default value to map"() { Map<String, String> letters = [:].withDefault{key -> DEFAULT_LETTER} assertThat(letters['oOo']).isEqualTo(DEFAULT_LETTER) }