Java Hello

// Define Static Method within a Class
public class HelloStatic {
    // Java standard runtime entry point
    public static void main(String[] args) {    
        System.out.println("Hello World!");
    }
}
// A method call allows us to execute code that is wrapped in Class
HelloStatic.main(null);   // Class prefix allows reference of Static Method

Hello World!

// Define Class with Constructor returning Object
public class HelloObject {
    private String hello;   // instance attribute or variable
    public HelloObject() {  // constructor
        hello = "Hello, World!";
    }
    public String getHello() {  // getter, returns value from inside the object
        return this.hello;  // return String from object
    }
    public static void main(String[] args) {    
        HelloObject ho = new HelloObject(); // Instance of Class (ho) is an Object via "new HelloObject()"
        System.out.println(ho.getHello()); // Object allows reference to public methods and data
    }
}
// IJava activation
HelloObject.main(null);

Hello, World!

// Define Class
public class HelloDynamic { // name the first letter of class as capitalized, note camel case
    // instance variable have access modifier (private is most common), data type, and name
    private String hello;
    // constructor signature 1, public and zero arguments, constructors do not have return type
    public HelloDynamic() {  // 0 argument constructor
        this.setHello("Hello, World!");  // using setter with static string
    }
    // constructor signature, public and one argument
    public HelloDynamic(String hello) { // 1 argument constructor
        this.setHello(hello);   // using setter with local variable passed into constructor
    }
    // setter/mutator, setter have void return type and a parameter
    public void setHello(String hello) { // setter
        this.hello = hello;     // instance variable on the left, local variable on the right
    }
    // getter/accessor, getter used to return private instance variable (encapsulated), return type is String
    public String getHello() {  // getter
        return this.hello;
    }
    // public static void main(String[] args) is signature for main/drivers/tester method
    // a driver/tester method is singular or called a class method, it is never part of an object
    public static void main(String[] args) {  
        HelloDynamic hd1 = new HelloDynamic(); // no argument constructor
        HelloDynamic hd2 = new HelloDynamic("Hello, Nighthawk Coding Society!"); // one argument constructor
        System.out.println(hd1.getHello()); // accessing getter
        System.out.println(hd2.getHello()); 
    }
}
// IJava activation
HelloDynamic.main(null);

Hello, World!
Hello, Nighthawk Coding Society!

Java Hello • 6 min read

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