A short code to add user to fire base database, with expanation

User.java

public class User(){
  public String username;
  public String email;
  
  public void User(){
  }
  public void User(String username, String email){
    this.username = username;
    this.email = email;
  }
  private void writeNewUser(String userId, String name, String email) {
    User user = new User(name, email);
    
    // The [users] is the root node and the [userId] the the setValue method is to add the object Users to the nde with the uderId.
    mDatabase.child("users").child(userId).setValue(user);
    
    /*Assume you are to change a users username then, here we are being specific*/
    mDatabase.child("users").child(userId).child("username").setValue(name);
}
}