![]() See the next step if you need a mutable list. Thus this list isn't truly immutable and a call to asList() should be wrapped with Collections.unmodifiableList(). It forbids modifications through some of the List API's methods by way of simply extending an AbstractList (so, adding or removing elements is unsupported), however it allows calls to set() to override elements. It's an inner type, which emulates an ArrayList but actually directly references the passed array and makes it "write through" (modifications are reflected in the array). Note that the returned type for asList() is a List using a concrete ArrayList implementation, but it is NOT. List l2 = Collections.unmodifiableList(Arrays.asList("element1", "element2")) ![]() Use the JDK's Arrays class and its asList() factory method, wrapped with a Collections.unmodifiableList(): List l1 = Collections.unmodifiableList(Arrays.asList(anArrayOfElements)) You do in one Guava call what takes 2 with the current Java Collections. However, this argument holds less water since Java 7 arrived with the new diamond operator.īut it's not the only reason (and Java 7 isn't everywhere yet): the shorthand syntax is also very handy, and the methods initializers, as seen above, allow to write more expressive code. The main attraction could be to reduce the clutter due to generics for type-safety, as the use of the Guava factory methods allow the types to be inferred most of the time. Please also note the similar methods for other data structures in other classes, for instance in Sets. List l3 = Lists.newArrayList("or", "string", "elements") // from varargs List l2 = Lists.newArrayList(aStringArray) // from array Use the Lists class and its newArrayList() factory methods: List l1 = Lists.newArrayList(anotherListOrCollection) // from collection List il = pyOf(aStringArray) // from array Use the ImmutableList class and its of() and copyOf() factory methods (elements can't be null): List il = ImmutableList.of("string", "elements") // from varargs It's worth pointing out the Guava way, which greatly simplifies these shenanigans: Usage For an Immutable List ![]() (old thread, but just 2 cents as none mention Guava or other libs and some other details) If You Can, Use Guava ![]()
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