Java中 Array、List、Set互相轉換

一：Array數組轉List 

String[] staffs = new String[]{"A", "B", "C"};
List staffsList = Arrays.asList(staffs);

//注意: 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("D"); // UnsupportedOperationException
staffsList.remove(0); // UnsupportedOperationException

//一下方式可以進行增刪操作。

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

二：數組轉Set

String[] staffs = new String[]{"A", "B", "C"};
Set<String> staffsSet = new HashSet<>(Arrays.asList(staffs));
staffsSet.add("D"); // ok
staffsSet.remove("Tom"); // ok

三：List轉數組

String[] staffs = new String[]{"A", "B", "C"};
List staffsList = Arrays.asList(staffs);

Object[] result = staffsList.toArray();

四：List轉Set

String[] staffs = new String[]{"A", "B", "C"};
List staffsList = Arrays.asList(staffs);

Set result = new HashSet(staffsList);

五：Set轉數組

String[] staffs = new String[]{"A", "B", "C"};
Set<String> staffsSet = new HashSet<>(Arrays.asList(staffs));

Object[] result = staffsSet.toArray();

六：Set轉List

String[] staffs = new String[]{"A", "B", "C"};
Set<String> staffsSet = new HashSet<>(Arrays.asList(staffs));

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