數組轉List

String[] staffs = new String[]{"Tom", "Bob", "Jane"};
List staffsList = Arrays.asList(staffs);

• 需要註意的是， Arrays.asList() 返回一個受指定數組決定的固定大小的列表。所以不能做 add 、 remove 等操作，否則會報錯。

  List staffsList = Arrays.asList(staffs);
  staffsList.add("Mary"); // UnsupportedOperationException
  staffsList.remove(0); // UnsupportedOperationException

• 如果想再做增刪操作呢？將數組中的元素一個一個添加到列表，這樣列表的長度就不固定了，可以進行增刪操作。

  List staffsList = new ArrayList<String>();
  for(String temp: staffs){
    staffsList.add(temp);
  }
  staffsList.add("Mary"); // ok
  staffsList.remove(0); // ok

數組轉Set

String[] staffs = new String[]{"Tom", "Bob", "Jane"};
Set<String> staffsSet = new HashSet<>(Arrays.asList(staffs));
staffsSet.add("Mary"); // ok
staffsSet.remove("Tom"); // ok

List轉數組

String[] staffs = new String[]{"Tom", "Bob", "Jane"};
List staffsList = Arrays.asList(staffs);

Object[] result = staffsList.toArray();

List轉Set

String[] staffs = new String[]{"Tom", "Bob", "Jane"};
List staffsList = Arrays.asList(staffs);

Set result = new HashSet(staffsList);

Set轉數組

String[] staffs = new String[]{"Tom", "Bob", "Jane"};
Set<String> staffsSet = new HashSet<>(Arrays.asList(staffs));

Object[] result = staffsSet.toArray();

Set轉List

String[] staffs = new String[]{"Tom", "Bob", "Jane"};
Set<String> staffsSet = new HashSet<>(Arrays.asList(staffs));

List<String> result = new ArrayList<>(staffsSet);