When 'new' is necessary and when is not ?

Question

The following codes were extracted from a book :
ArrayList<Account>  things = new ArrayList<Account>();
things.add(new Account());
Account myAccount = things.get(0);Question:
The 3rd line didn't have 'new' keyword, does it mean that myAccount is storing a reference to the 1st item of 'things' instance ? So to say, myAccount itself doesn't an instance of its own for Account class. Am I right ?

Answer 1

JoachimSauer wrote:
System.identityHashCode() comes closest to the memory address of an object. It returns a almost-unique number that is derived from the object identity alone. It doesn't change when an objects values chane, it stays constant for the objects life time, and the result for two different objects is (almost always!) different.Depends on your definition of "almost always." :-)
I usually get duplicated hashcodes after just a couple thousand objects with this code.
import java.util.*;
public class HC {
    public static void main(String[] args) {
        Map<Integer, List<Object>> map = new HashMap<Integer, List<Object>>();
        for (long ix = 0; true; ix++) {
            Object obj = new Object();
            int hc = obj.hashCode();
            if (map.containsKey(hc)) {
                List<Object> list = map.get(hc);
                list.add(obj);
                System.out.println("Iteration " + ix + ", hc=" + hc + ", count="
                        + list.size());
            else {
                List<Object> list = new ArrayList<Object>();
                list.add(obj);
                map.put(hc, list);
}