Encapsulation is whereby variables, functions are protected from being accessed by other codes outside the class. This helps manage the code being protected and has least if any impact on other parts of a program if change was to occur in the protected code.
Encapsulation is important in java due to its flexibility and it is easy to change with new requirement, the class has total control over what is stored in its field, one part of the code can be changed and the rest of the would not be affected and also encapsulation is useful since it is easy to maintain. Both the mutator and accessor method are used to enforce data encapsulation where their jobs is returning and setting the value state of an object. Mutator method is used to set the private field value. It is denoted by using set at the beginning of the method name. Example of a mutator method would be public void setSchool (String school). Accessor method is used to return the private field value. It is denoted by using get at the beginning of the method name. An example of accessor method would be public String getFirstName () Implicit parameter is the object on which the method is invoked whereas explicit parameter is the parameter of the method other than the object the method is invoking and is enclosed in a parentheses. To access an explicit parameter variable inside the method refer the parameter variable by its name. To illustrate what is an implicit and explicit parameter we use the following code: Person p = newPerson() p.name(“Chris”) chris is the explicit parameter while the obkect p is the implicit parameter. A constructor is used to create an object of the class that is in by initializing all the variables and also creates a location in memory where the object is held. A constructor uses the word new followed by the class name example of a constructor that constructs a new String Object: new String() A class can have as many constructors as long as each constructor has a different parameter list. A class does not necessarily require it to have a constructor. This is because if a class does not have a constructor, java automatically creates a default constructor for the class. When a class has more than one constructor, the constructor gets called depending on the arguments of the object that has being created for the class. To illustrate this we use the following program { private: int m,n; Public: integer(){m=0; n=0;} Integer(int a, int b) {m=a; n=b; } Integer(integer & i) {m=i.m; n=i.n} };
In the above program we have declared three constructors for the object integer where the first constructor receives no argument, the second receives two integer argument and finally the third receives one integer object as an argument. Depending on the argument used of the object created for the class the constructor will be called.