陣列轉List

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

需要注意的是， Arrays.asList() 返回一個受指定陣列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？將陣列中的元素一個一個新增到列表，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

陣列轉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轉陣列

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轉陣列

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);