那位能给我解释一下这编程例题？详细点
class Book {boolean checkedOut = false;
Book (boolean checkOut) {
checkedOut = checkOut;
}
void checkIn () {
checkedOut = false;
}
protected void finalize () {
if (checkedOut)
System.out.println("Error: checked out");
//Normally,you'll also do this;
//supper.finalize(); //Call the base-class version
}
}
public class TerminationCondition {
public static void main (String[] args) {
Book novel = new Book (true);
// Proper cleanup;
novel.checkIn();
//Drop the reference, forget to clean up;
new Book (true);
//Force garbage collection & finalization;
System.gc();
}
}
