[b]1.list转set [/b]Set set = new HashSet(new ArrayList());  [b]2.set转list [/b]List list = new ArrayList(new HashSet()); [b]3.数组转为list [/b]List stooges = Arrays.asList("Larry", "Moe", "Curly"); 或者 String[] arr = {"1", "2"}; List list = Arrays.asList(arr); [b]4.数组转为set [/b]int[] a = { 1, 2, 3 }; Set set = new HashSet(Arrays.asList(a)); [b]5.map的相关操作。 [/b]Map map = new HashMap(); map.put("1", "a"); map.put('2', 'b'); map.put('3', 'c'); System.out.println(map); // 输出所有的值 System.out.println(map.keySet()); // 输出所有的键 System.out.println(map.values()); // 将map的值转化为List List list = new ArrayList(map.values()); System.out.println(list); // 将map的值转化为Set Set set = new HashSet(map.values()); System.out.println(set); [b]6.list转数组 [/b]List list = Arrays.asList("a","b"); String[] arr = (String[])list.toArray(new String[list.size()]); System.out.println(Arrays.toString(arr));