Why does this work:
String[] array = {"a", "b", "c"}; List<String> list = Arrays.asList(array);
but this does not:
List<String> list = Arrays.asList({"a","b","c"});
The asList() method of java. util. Arrays class is used to return a fixed-size list backed by the specified array. This method acts as a bridge between array-based and collection-based APIs, in combination with Collection.
asList method. Using this method, we can convert from an array to a fixed-size List object. This List is just a wrapper that makes the array available as a list. No data is copied or created.
This is a short hand only available when constructing and assigning an array.
String[] array = {"a", "b", "c"};
You can do this though:
List<String> list = Arrays.asList("a","b","c");
As asList
can take "vararg" arguments.
Your question is why one works and the other does not, right?
Well, the reason is that {"a","b","c"}
is not a valid Java expression, and therefore the compiler cannot accept it.
What you seem to imply with it is that you want to pass an array initializer without providing a full array creation expression (JLS 15.10).
The correct array creation expressions are, as others have pointed out:
String[] array = {"a", "b", "c"};
As stated in JLS 10.6 Array Initializers, or
String[] array = new String[]{"a", "b", "c"};
As stated in JLS 15.10 Array Creation Expressions.
This second one is useful for inlining, so you could pass it instead of an array variable directly.
Since the asList
method in Arrays
uses variable arguments, and variable arguments expressions are mapped to arrays, you could either pass an inline array as in:
List<String> list = Arrays.asList(new String[]{"a", "b", "c"});
Or simply pass the variable arguments that will be automatically mapped to an array:
List<String> list = Arrays.asList("a","b","c");
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With