What entities participate in creating a Java Bean?

Entities involved in creating a Java Bean:

1. Properties. Represent the state of the object. Accessor methods must be defined for each property.
2. Accessor Methods.
   • Getters: Methods to retrieve property values. They start with get (or is for boolean properties) and return the property value.
   • Setters: Methods to set property values. They start with set and accept one parameter, which is the new value for the property.
3. No-argument constructor. A Java Bean must have a public no-argument constructor. This allows instantiating the object without providing initial values, which is important for many frameworks (e.g., serialization, visual design tools, IoC containers).
4. (Optional) Events. Beans can generate events to notify other listeners about changes in their state. This is done using methods based on the Observer pattern.
5. (Optional) Methods. The Bean can have other public methods providing functionality not directly related to property access.

Example structure of a Java Bean:

public class SimpleBean { // The class must be public

    private String name; // Private field
    private int age;     // Private field

    // Public no-argument constructor
    public SimpleBean() {
    }

    // Getter for the name property
    public String getName() {
        return name;
    }

    // Setter for the name property
    public void setName(String name) {
        this.name = name;
    }

    // Getter for the age property
    public int getAge() {
        return age;
    }

    // Setter for the age property
    public void setAge(int age) {
        this.age = age;
    }

    // Another optional method
    public void displayInfo() {
        System.out.println("Name: " + name + ", Age: " + age);
    }
}