java中List、Array、Map、Set等集合相互转换的最佳方法

1.List转换为Array

List<String> list = new ArrayList<String>();
list.add("China");
list.add("Switzerland");
list.add("Italy");
list.add("France");
String [] countries = list.toArray(new String[list.size()]);

2.Array转换为List

String[] countries = {"China", "Switzerland", "Italy", "France"};
List list = Arrays.asList(countries);

3.Map转换为List

List<Value> list = new ArrayList<Value>(map.values());

4.Array转换为Set

String [] countries = {"India", "Switzerland", "Italy"};      
Set<String> set = new HashSet<String>(Arrays.asList(countries));
System.out.println(set);

5.Map转换为Set

Map<Integer, String> sourceMap = createMap();
Set<String> targetSet = new HashSet<>(sourceMap.values());