打印数组的方法，小地方，却老忘记，来自FindBugs的提示：
The code invokes toString on an array, which will generate a fairly useless
result such as [C@16f0472. Consider using Arrays.toString to convert the array
into a readable String that gives the contents of the array.
Arrays提供一系列接收不同类型数组作为参数的toString方法
String[] array = new String[]{"a","b","c"};
System.out.println(Arrays.toString(array));