Collections.emptyList(),Collections.EMPTY, Collections.EMPTY_LIST, new ArrayList

Collections.EMPTY_LIST:

public class Collections {
    public static final List EMPTY_LIST = new EmptyList<>();
}

 private static class EmptyList<E>
        extends AbstractList<E>
        implements RandomAccess, Serializable {
        private static final long serialVersionUID = 8842843931221139166L;
......
}

Collections.emptyList():

Class Collections{
    public static final <T> List<T> emptyList() {
        return (List<T>) EMPTY_LIST;
    }
    public static final List EMPTY_LIST = new EmptyList<>();
}   

 private static class EmptyList<E>
        extends AbstractList<E>
        implements RandomAccess, Serializable {
        private static final long serialVersionUID = 8842843931221139166L;
......
}

ArrayList:

Class ArrayList{
        transient Object[] elementData;
        private static final Object[] DEFAULTCAPACITY_EMPTY_ELEMENTDATA = {};
        public ArrayList() {
            this.elementData = DEFAULTCAPACITY_EMPTY_ELEMENTDATA;
        }
}

Summary: Collections.EMPTY and Collections.empty() are both empty lists and share the same one, because EMPTY_LIST is statically modified (public static final List EMPTY_LIST = new EmptyList<>();), the difference is that emptyList() can Specify the return type via generics. And new ArrayList(), the object created each time is different, so it will take up space in comparison.