Converting an array into a list in Java requires selecting methods based on the data type and requirements. ① Use Arrays.asList() to quickly convert an object array (such as String[]) into a fixed-size List, but elements cannot be added or deleted; ② If you need a mutable list, you can encapsulate the result of Arrays.asList() through the ArrayList constructor; ③ For basic type arrays (such as int[]), you need to use the Stream API to convert, such as Arrays.stream().boxed().collect(Collectors.toList()); ④ Notes include avoiding null arrays, distinguishing basic types from object types, and explicitly returning whether the list is mutable. Mastering these methods can deal with most scenarios.
It is not difficult to convert an array (Array) into a list (List) in Java, but the methods are slightly different in different data types and usage scenarios. If you just want to know how to convert quickly, the most common way is to use Arrays.asList() method. However, it should be noted that the List produced in this step is of a fixed size and cannot be added or deleted at will.
Use Arrays.asList() to convert an array of primitive types
This is the most commonly used method and is suitable for object arrays. for example:
String[] array = {"apple", "banana", "orange"};
List<String> list = Arrays.asList(array); But note that this method is not suitable for directly processing arrays of basic data types (such as int, char) . For example, if you have an int[] , and passing it directly to asList() will get a List<int[]> instead of the multiple integer terms you expect.
If you want to convert the primitive type array to a real List, you can do this:
- Manually traverse the array and add new ArrayList one by one.
- Or use Java 8's Stream API:
int[] intArray = {1, 2, 3};
List<Integer> list = Arrays.stream(intArray).boxed().collect(Collectors.toList());Create mutable lists using the ArrayList constructor
Arrays.asList() returns a fixed-size List and cannot call add() or remove() . If you need a list that can be modified, you can use this method:
String[] array = {"red", "green", "blue"};
List<String> list = new ArrayList<>(Arrays.asList(array));This way you get a standard ArrayList that can add or remove elements.
Note: Avoid common pitfalls
There are a few easy points to get stuck during the conversion process:
- Don't make an error when the array is empty : If the array is null, passing it directly to
asList()will throw an exception. Remember to determine whether it is null first. - Confusing basic type arrays : As mentioned earlier,
int[]is not suitable to useasList()directly, otherwise the result is not what you want. - Is the returned List variable : Remember that the List obtained by
Arrays.asList()cannot be expanded and can only be encapsulated into a new ArrayList to operate freely.
Basically that's it. By mastering these methods, you can deal with most array conversion scenarios.
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