How to implement array conversion in Java collections

1. toArray() method

You can use the toArray() method in List to convert the List into an array. Note: If there are no parameters in the toArray() method, it will be returned. It is an object type array. If it is of string type, you need to add: new String[list.size()];

List<String> list=new ArrayList<String>();
list.add("aa");
list.add("bb");
list.add("cc");
String[] array=list.toArray(new String[list.size()]);

2. Generate List

String[] array=new String[]{"aa","bb","cc"};
List<list> list=Arrays.asList(array);

Note : The List generated by the above method cannot perform addition or deletion operations. The following operations have no such restrictions.

String[] array=new String[]{"aa","bb","cc"};
List<String> list=new ArrayList<String>();
Collections.addAll(list,array);

What collection classes are there in Java?

Collections in Java are mainly divided into Four categories:

1. List: ordered and repeatable;

2. Queue: ordered and repeatable;

3. Set : Non-repeatable;

4. Map mapping: unordered, unique keys, not unique values.

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