集合数组相互转换

//集合转数组
List<String> list = new ArrayList<String>(2);
list.add("guan");  
list.add("bao");
String[] array = new String[list.size()]; 
array = list.toArray(array);

//数组转集合 Sring[] -> list<String> list
list.toArray(new String[0])