New to Java, and trying to solve the main part of the exercise for the OldMacdonald Had a Farm song

I am trying to code a song using polymorphism, but I am quite new to Java coding and have a really basic experience. I could use some help with the classes, but my biggest problem is that I do not know how to write the main part of the code, I'd be very grateful if someone could help me with it.

Here is what I have so far

public class OldMacdonald {
public interface Farm{
public String getName();
public String getNoise();
}
class Dog implements Farm{
String name;
String noise;
public Dog(String name, String noise) {
name=name;
noise=noise;
}
public String getName() {
return name;
}
public String getNoise() {
return noise;
}
}
class Cat implements Farm{
String name;
String noise;
public Cat(String name, String noise) {
name=name;
noise=noise;
}
public String getName() {
return name;
}
public String getNoise() {
return noise;
}
}
class Duck implements Farm{
String name;
String noise;
public Duck(String name, String noise) {
name=name;
noise=noise;
}
public String getName() {
return name;
}
public String getNoise() {
return noise;
}
}
class Cow implements Farm{
String name;
String noise;
public Cow(String name, String noise) {
name=name;
noise=noise;
}
public String getName() {
return name;
}
public String getNoise() {
return noise;
}
}
class Pig implements Farm{
String name;
String noise;
public Pig(String name, String noise) {
name=name;
noise=noise;
}
public String getName() {
return name;
}
public String getNoise() {
return noise;
}
}
class Song{
private Farm [] animal = new Farm[5];
Song() {
animal[0] = new Dog("dog", "woof");
animal[1] = new Cat("cat", "meow");
animal[2] = new Duck("duck", "quack");
animal[3] = new Cow("cow", "moo");
animal[4] = new Pig("pig", "oink");
}
public void lyrics() {
int i;
for(i=0; i<animal.length; i++) {
System.out.println("Old MacDonald had a farm, E I E I O,\r\n" + 
"And on his farm he had a " + animal[i].getName() + ", E I E I O.\r\n" + 
"With a " + animal[i].getNoise() + " " + animal[i].getNoise() + " here and a " + animal[i].getNoise() + " " + animal[i].getNoise() + " there,\r\n" + 
"Here a " + animal[i].getNoise() + ", there a " + animal[i].getNoise() + ", evrywhere a " + animal[i].getNoise() + " " + animal[i].getNoise() + ".\r\n" + 
"Old MacDonald had a farm, E I E I O.\r\n\r\n");
}
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
}

}

You need to "launch" your code somehow, in a Java standalone program like this that would be done from the main method:

public static void main(String[] args)

It looks like Song is your class that actually starts everything off so you need to create an instance of that:

public static void main(String[] args) {
Song mySong = new Song();
}

The lyrics are output by the lyrics() method, so we need to call that:

public static void main(String[] args) {
Song mySong = new Song();
mySong.lyrics();
}

You'll want to tweak your Song() constructor method too:

public Song() {

You might want to update your constructors in animal classes too, you were assigning the parameter to itself (easily done when using same names for variables in params and private fields):

public Cat(String name, String noise) {
this.name = name;
this.noise = noise;
}

If I understood you correctly, in your main()method you just have to create an instance of Song and call lyrics() on it, no? That will populate the Farm array with the animals and call the appropriate methods when printing the lyrics.