1. Convertir lista en matriz
List<String> list = new ArrayList<>();
list.add("AAAA");
list.add("BBBB");
list.add("CCCC");
list.add("DDDD");
System.out.println(list);//输出 [AAAA, BBBB, CCCC, DDDD]
String [] array = list.toArray(new String[list.size()]);
2. Convertir matriz en lista
String[] countries = {
"AAAA", "BBBB", "CCCC", "DDDD"};
List list = Arrays.asList(countries);
System.out.println(list);//输出[AAAA, BBBB, CCCC, DDDD]
3. Convertir matriz en conjunto
String [] countries = {
“AAAA”, “BBBB”, “CCCC”, “DDDD”};
Set<String> set = new HashSet<String>(Arrays.asList(countries));
System.out.println(set);//输出[AAAA, BBBB, CCCC, DDDD]
注:如果Array中存在相同的值,Set中只会存在一个