数组转集合：asList()方法
String[] arr ={"123","456","789"};
List<String> list = Arrays.asList(arr);
集合转数组：toArray()方法
ArrayList<String> al = new ArrayList<String>();
al.add("abc1");
al.add("abc2");
al.add("abc3");
String[] arr = al.toArray(new String[al.size()]),

数组转集合：asList()方法
String[] arr ={"123","456","789"};
List<String> list = Arrays.asList(arr);
集合转数组：toArray()方法
ArrayList<String> al = new ArrayList<String>();
al.add("abc1");
al.add("abc2");
al.add("abc3");
String[] arr = al.toArray(new String[al.size()]),