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OCP - 1

Classes, Desing Patterns, Principles, Generics and Collections

Classes, Desing Patterns, Principles, Generics and Collections

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Karten 124
Sprache English
Kategorie Informatik
Stufe Andere
Erstellt / Aktualisiert 31.01.2019 / 08.01.2020
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What is the signature of Map.merge?

V merge(K key, V value, BiFunction<? super V,? super V,? extends V> remappingFunction)

What does the Map.merge method do?

merge(key, value,function)

  • If the the value for the given key is null or not present, insert the provided value.
  • Otherwise, replace the value for the given key with the result of function
    • function takes the value from the map as the first argument and the new value as the second one.

Map<String, String> leMap = new HashMap<String, String>();

String result;
result = leMap.merge("key", "v1", (k1, k2) -> k1 + k2);
result = leMap.merge("key", "v2", (k1, k2) -> k1 + k2);
result = leMap.merge("key", "v3", (k1, k2) -> k1 + k2);

System.out.println(result);

When defining an enum, where do the static method values() and valueOf() come from?

The compiler generates it on the enum class

When defining an enum, where do the methods name() and ordinal() come from?

All enums implicitly extend the enum in which these methods are defined

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