public enum introToEnum {
    //enum is converted to class internally.
    //all enums extend java.lang.Enum class. so it cannot extend anything else.
    ELSS("ELSS"),
    //this means ELSS is one of the enum.
    // this gets converted to --> public static final introToEnum ELSS = new introToEnum("ELSS");
    UNKNOWN("UNKNOWN");

    private final String value;
    //we can have instance variables.

    introToEnum(String value) {
        this.value = value;
    }
    //this is private constructor. so enum can't be instantiated.
    //this is invoked for each enum value.


    public String getValue() {
        return value;
    }
    //we can only have concrete methods inside enum.
}