In order to enable configuration of a class variable from a properties file, the class defines setX() and getX() methods for that variable, where X specifies the variable/property to configure.

For example, to make the variable age configurable from the property age, the class defines setAge() and getAge() methods:

int age;
public void setAge (int age) { this.age = age; }
public int getAge () { return age; }

Exposing a variable as a property also exposes it to runtime inspection by the Nucleus administrator.

You might also wish to make a property read-only, meaning that it can be inspected at runtime but cannot be configured through a properties file. This technique is often used for properties that contain runtime statistics. To make a property read-only, simply omit the setX function:

int age;
public int getAge () { return age; }