A class-level security is one in which a caller can call any method of any instance of a class. The declarative security is a class-level security. It is different from an instance-level security in which a caller is allowed to call methods of only a particular instance of a class. Programmatic security is an instance-level security.

The LinkedList class defines the following methods for manipulating lists. These are as follows:

void addFirst(E obj): This method inserts an element at the beginning of the list.
void addLast(E obj): This method inserts an element at the end of a list
>E getFirst(): This method is used to retrieve the first element from the list.
E getLast(): This method retrieves the last element from the list.
E removeFirst(): This removes the first element from the list.
E removeLast(): This method removes the last element from the list.
Here, obj specifies the item.

A constructor provides a convenient way to initialize a newly created object at the time of its creation. It is defined for a class and it is called automatically immediately after the creation of a new object, but before the new operator completes. All Although constructors look the same as methods, they are written by using the following conventions:

1. A constructor is always given the name of the class in which it is defined.
2. A constructor is always written without an explicit return type, not even void. This is because the implicit return type of a class constructor is the class itself.

The FileInputStream class is used to is used to read binary data from a file. It is used to perform simple file input operations. It reads data in a sequential manner, but can skip a region of data as per requirement. It generally reads data in a sequential manner, but can skip a region of data as per requirement. FileInputStream class can be instantiated by using any of the following three constructors: