Data Structures and Algorithms in Java[1].pdf - Fulvio Frisone

Each of the pieces of this declaration have important uses, which we describe in
detail in this section. The modifiers part includes the same kinds of scope modifiers
that can be used for variables, such as public, protected, and static, with similar
meanings. The type part of the declaration defines the return type of the method.
The name is the name of the method, which can be any valid Java identifier. The
list of parameters and their types declares the local variables that correspond to the
values that are to be passed as arguments to this method. Each type declaration type i
can be any Java type name and each parameter i can be any Java identifier. This list
of parameters and their types can be empty, which signifies that there are no values
to be passed to this method when it is invoked. These parameter variables, as well
as the instance variables of the class, can be used inside the body of the method.
Likewise, other methods of this class can be called from inside the body of a
method.
When a method of a class is called, it is invoked on a specific instance of that class
and can change the state of that object (except for a static method, which is
associated with the class itself). For example, invoking the following method on
particular gnome changes its name.
public void renameGnome (String s) {
name = s; // Reassign the name instance variable
of this gnome.
}
Method Modifiers
As with instance variables, method modifiers can restrict the scope of a method:
• public: Anyone can call public methods.
• protected: Only methods of the same package or of subclasses can call a
protected method.
• private: Only methods of the same class (not methods of a subclass) can
call a private method.
• If none of the modifiers above are used, then the method is friendly.
Friendly methods can only be called by objects of classes in the same package.
The above modifiers may be preceded by additional modifiers:
• abstract: A method declared as abstract has no code. The signature of
such a method is followed by a semicolon with no method body. For example:
public abstract void setHeight (double newHeight);
36