Java attributes and methods

Java Attributes and Methods in the HMIS System

Java attributes and methods are essential parts of HMIS development.

Attributes store information such as:

• Patient name
• Patient code
• Bill total
• Created date
• Department
• Investigation
• Report status
• Retired status

Methods are used to:

• Read attribute values
• Change attribute values
• Validate data
• Calculate totals
• Process reports
• Search database records
• Clear filters
• Format information for display

A simple HMIS-style example is:

private String patientCode;

private double total;

private boolean retired;

public String getPatientCode() { return patientCode; }

public void setPatientCode(String patientCode) { this.patientCode = patientCode; }

public double calculateNetTotal(double discount) { return total - discount; }

In this example:

• patientCode, total, and retired are attributes.
• getPatientCode(), setPatientCode(), and calculateNetTotal() are methods.

1. Java Attributes

An attribute stores data inside a Java component. Attributes are also called:

• Fields
• Member variables
• Instance variables
• Properties, especially when accessed through getters and setters

General syntax : accessModifier dataType attributeName;

private String patientName;

• private is the access modifier.
• String is the data type.
• patientName is the attribute name.

Exmples

• private Long id;
• private String patientCode;
• private Date createdAt;
• private Department department;
• private Investigation investigation;
• private boolean retired;
• private List results;

Attribute Declaration

An attribute can be declared without an initial value.

private String patientName;

It can also be declared with an initial value.

private boolean retired = false;

A collection should often be initialized immediately.

private List results = new ArrayList<>();

This is safer than:

private List results;

because using an uninitialized list may cause a NullPointerException.

For example :

results.clear();

will fail when results is null.

Attribute Data Types

Attributes may use primitive types or reference types.

Primitive attributes

private int patientCount;

private long recordCount;

private double total;

private boolean retired;

private char categoryCode;

• Primitive types cannot contain null.

Reference attributes

private String patientName;

private Date createdAt;

private Department department;

private Investigation investigation;

private List bills;

• Reference attributes can contain null.

Primitive and Wrapper Attributes

Primitive

• int
• long
• double
• boolean
• char
• float
• short
• byte

Wrapper

• Integer
• Long
• Double
• Boolean
• Character
• Float
• Short
• Byte

Example:

private boolean retired;

private Boolean approved;

retired can contain:

• true
• false

approved can contain:

• true
• false
• null

Use primitive types when a value must always exist. And use wrapper types when the value may be unknown or nullable. For database query projections and DTO attributes, wrapper types are often safer.