How to have all my classes default functionalities like .ToString method

fixed the issue. Will look into that further It took some time to understand your (confusing) question. I can suppose that you are speaking about primitive wrapper classes like Integer or Long that indeed have several overloaded static methods toString(). But each one of them has different signature.
The toString() method defined in java.lang.Object that can be overridden by subclasses does not accept arguments. The static methods toString that can be found in other classes (e.g. java.lang.Integer) accept arguments (e.g. public static String toString(int i), public static String toString(int i, int radix) etc)

Does that help Actually in ES6 "class" is just a function. So to understand how toString behave for so-called "classes" you must look at toString() specification for function. It says:

class Foo {
    // some very important constructor
    constructor() {
       // body
    }

    /**
     * Getting some name
     */
    getName() {
    }
}

Foo.toString() === `class Foo {
    // some very important constructor
    constructor() {
       // body
    }

    /**
     * Getting some name
     */
    getName() {
    }
}`;

like below fixes the issue No. You can't override the system's Enum class, and you cannot make a subclass from which all of your Enums inherit from as it is a language feature with a lot of special rules. However, you can make a static helper method:

public class Utils {
  public static String toEnumString(Enum<?> inputEnum) {
    return inputEnum.name().charAt(0) + inputEnum.name().substring(1).toLowerCase();
  }
}

enum Coins { PENNY(1), POUND(100), NOTE(500); 

  // snip 
  public String toString() {
    return Utils.toEnumString(this);
  }
}

System.out.println(Utils.toEnumString(Coins.PENNY));
preparedStatement.setString(1, Utils.toEnumString(Coins.POUND));

Does that help
Is there a way to use the second function without specifying parameters or renaming the function?