Hello World with extensive documentation.

Test.java

// Open up a new project called Test
// Make a new class called Test

//Now try this code

public class Test {
    public static void main(String[] args) {
        System.out.println("Hello World");
    }
}

//

// When java runs a program, it looks for the main class. This is usually handled
// by your editor, but the key thing to note is that for all class files, the public
// class must have the same name (case sensitive) of that of the file (Test.java).
public class Test {
    
    
    // Inside the main class, there must contain the main function. This method is
    // static, since it exists outside the instance of the class Test. You don't have to
    // understand that for now, as it involves an understanding of Object Oriented Programming.
    
    // The main function is also a void. A function must return something, be it a String
    // (a collection of characters (letters/numbers/etc)) or a number, or an object. However
    // you can also return nothing, which is what void implied. That the function returns nothing.
    
    // Inside the brackets, we have String[]. I mentioned String earlier, but the [] part is
    // new. It implies that it's actually an Array of Strings. An array is a collection of things
    // that are the same type. In this case, they are all Strings.
    
    // "args" is a variable name. For here, args is the name assosiated with the array of Strings
    // we mentioned earlier. In other worlds, args is an array of Strings.
    
    // The curly braces are there to help you and the computer understand what code is within
    // the scope of the function. So when we call this function, everything between { and } will be run.
    
    // The world public implies this function can be accessed outside of the class. In this case
    // the Java Virtual Machine needs to call this function inside this main class in order to run
    // the program.
    public static void main(String[] args) {
    
        // System.out.println() is a function. In fact, it's a static function like this one we're in.
        // This function will print the String we enter as an argument, to our console.
        
        // "" are used to show the start, and end of a String hardcoded into the program.
        System.out.println("Hello World");
    }
}