"The compiler doesn’t know the exact type of the setFirst method but can call it with any object of type Manager, Employee , or Object , but not a subtype such as Executive . However, if you call getFirst , there is no guarantee about the type of the returned object. You can only assign it to an Obje"
"它将Welcom.java编译成Welcom.class,并发送到Java虚拟机。"
"java.math.BigInteger 1.1"
"数组to必须有足够空间存放拷贝的元素。"
"由类构造(construst)"
"特别需要说明,如果一个类使用了这样的方法,当对象不再使用时一定要调用它。"
"Just as importantly, if a class you use has such a method, you need call it when you done with the object."