ECLIPSE IDE - Creating "getters" and "setters" Eliminating Tedious Programming Tasks

Fundamental Elements of a Class Definition

When we create a class specification, which is really the blueprint for object creations we can think of three fundamental elements:

  • fields or class variables - this are items such as a person's name, a street address, a city name.
  • a constructor - which sets initial values for the class variables.
  • methods - procedures or functions which are used to retrieve or modify data.


"getter" and "setter" Methods

These are the names for the two methods which modify a variable. "setters" set a value of a field. An example would be instantiated or setting the value "Fred" to a field variable firstName.

A "getter" is a method of retrieving the value for a field. For example a "getter" method for firstName can can be used with a method for perhaps printing out the name.

The following snapshot illustrates a simple class definition for the class BillingAddress.

Start ECLIPSE and Create/Select a Workspace

My workspace is worspaceGS
My workspace is worspaceGS

Create a Project, Package and Class

After New   Project we have the option to modify build. At this point we take all defaults.
After New Project we have the option to modify build. At this point we take all defaults. | Source
The standard naming convention is to specify the name of your organization, generally a URL as illustrated.
The standard naming convention is to specify the name of your organization, generally a URL as illustrated. | Source
Source

Creating the Class Fields

A number of fields are added to the class. Notice that this is what one would expect as a "barebones' example which could be used for invoicing and creating shipping labels.Our class has variables of two types: strings, for names, and int (integers) for the zipcode.

The Class Definition Thus Far

The class fields for the BillingAddress class have been entered.
The class fields for the BillingAddress class have been entered.

Creating "getters" and "setters" Methods

At this point, we would begin creating methods to set and retrieve values for the class fields.

A standard "setter" method would look like:

public void setState(String anything) {

state = anything;

}


We use the word "public" to specify that this method will be visible outside of the class. That is an application developer would be able to use this method in their code. This contrasts with "private" which basically says that the method is "hidden", inaccessible and unknown outside of the class.

The word "void" indicates that this method does not return any value.

The "String anything" indicates the parameter to be passed into the method is a string. A state name is a string of characters (e.g. "Minnesota").

The next line would assign the string to the value specified by the local variable anything. Thus if the method was called with anything, the resulting value of the state variable for its object instance would be, in our example "Minnesota".

The "getter" method would be coded as follows:

public String getState() {

return state;

}


The meaning of "public" is as it was previously defined. String indicates the type of value being returned. The return statement states that the method will return the value stored in the variable state.

As one can see in this rather simple example, this processes is simple and would have to be repeated for each of the fields defined for the class. Not only is it tedious, but it is also prone to error.

Eclipse has an automated way for handling creation of "getters" and "setter".

At this point we have the class open, choose from the menu Source > Generate Getters and Setters.

The ECLIPSE "magic" is illustrated in the following snapshot.




Selecting the Otion to Generate"getters" and "setters"

Choosing the option to create getters and settters.
Choosing the option to create getters and settters.
We select all fields for ECLIPSE to generate "getters" and "setters".
We select all fields for ECLIPSE to generate "getters" and "setters".

Snapshot of the Code ECLIPSE Generated

The code ECLIPSE generated for each of the fields in the class.
The code ECLIPSE generated for each of the fields in the class.

What is "this."?

You may note some small differences in the code ECLIPSE generated from my hand generated code.

My "setter" method was:

public void setState(String anything) {

state = anything;

}

while ECLIPSE generated:

public void setState(String state) {

this.state = state;

}

While the "getter" method was exactly the same.

ECLIPSE used the argument state to pass in to the method and then sets this.state to state. This is very confusing!! One must remember that the value passed in as a parameter is merely a place holder. It is a local variable. As my example indicated, I used the name anything because it doesn't matter what the variable name is provided it was properly assigned.

The this. is used to help alleviate confusion. It is simply intended to indicate that the value is assigned to a particular occurrence of the field state in an instance of an object. The this. is not required the assignment statement could have been coded:

state = state;

Now that is confusing.. The this. is a helpful reminder that we are assigning a local variable state to a particular occurrence (instance) of the object variable state.



Wrap-up and What's Next!

To conclude this lesson we have introduced a number of things which you may be unfamiliar with, Don't worry, we'll repeat them frequently throughout these tutorials. Consider it a process, like learning a language. There are two approaches: one show all the rules and learn thing by rote or use a process of discovery as things are necessary. When I went to Germany years ago, the first words I learned related to food, because it was a necessity. My vocabulary increased or evolved as needed.

In this tutorial we have touched on:

  • creating a class
  • creating class fields and methods
  • setting and getting values to the fields
  • allowing ECLIPSE to generate this code

Our next tutorial will look at experimenting with JAVA expressions and statements with the help of the ECLIPSE scrapbook pages.

JAVA Class Quiz

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