This is driving me mad. (Map problem...)

Question

I've been programming a java text-based game for quite a while now. Unfortunately I'm having a problem.
Simple version---
For some reason I use thismap = thatmap. And when I modify thatmap it also changes thismap
Long Version---
First I have a map for the itemtemplate to be copied.
Next it copies the itemtemplate into a newmap(thisitem).
Next it replaces the name in thisitem to the new name(so that each item has a different name).
Next i put that item in the itemmap for the user. Then I replace the key "items" in Map user with the updated itemmap.
For some reason when I change the name in thisitem, it also changes the name in the template otemp1. This is the problem
Here is where the problem seems to be-
Map thisitem = otemp1;
thisitem.put("name",iname);
items.put(iname,thisitem);
newmap.put("items",items);
users.put(newmap.get("name"),newmap);
otemp1.put("name",itembase);
System.out.println(newmap.get("items").toString());
The code---
if (action.indexOf("giveitem")==0) {
String actionparts[] = action.split("#");
//giveitem#templatename
Map items;
if (newmap.containsKey("items")) {
items = (Map) newmap.get("items");
} else {
items = new HashMap();
if (itemtemplates.containsKey(actionparts[1])) {
Map otemp1;
otemp1 = (Map) itemtemplates.get(actionparts[1]);
if (!otemp1.containsKey("alwayscalled")) {
String itembase = otemp1.get("name").toString();
int x = 1;
String iname = "" + itembase + x;
System.out.println(otemp1.get("name").toString());
//this method is to add a number to the end, such as
//potion5 so that a user doesn't have multiple items with the same name
while ( items.containsKey(iname) ) {
iname = "" + itembase + x;
x = x + 1;
System.out.println("itembase:"+itembase+" iname:"+iname+" x:"+x);
System.out.println("CREATING:"+iname);
Map thisitem = otemp1;
thisitem.put("name",iname);
items.put(iname,thisitem);
newmap.put("items",items);
users.put(newmap.get("name"),newmap);
otemp1.put("name",itembase); //See Note 1
System.out.println(newmap.get("items").toString());
} else {
otemp1.put("name",otemp1.get("alwayscalled"));
items.put(otemp1.get("alwayscalled"),otemp1);
newmap.put("items",items);
users.put(newmap.get("name"),newmap);
//name=gold1~type=gold~takeable=true~amt=100~at=Ashgavh1
//Map itemmap1 = new HashMap();
//itemmap1.put("name",goldbase+z);itemmap1.put("type","gold");
//itemmap1.put("amt","100");
//itemmap1.put("takeable","true");itemmap1.put("at",newmap.get( "location" ));
//objects.put(goldbase+z, itemmap1);
} else {
System.out.println("ERROR:Give Item Failure(No Template FOR "+callingobj+").");
//objects.put(
note1
That was my first attempt to fix it, but that changes the items name in the Map user.get("items") also!! Why? I feel like I'm going to scream. Thanks to anyone who can help me.

Answer 1

thismap and thatmap are not objects. They're just references--pointers to objects.
thatmap = thismap doesn't copy the map. Assignment with = never copies objects in Java. All it does is cause thatmap to point at the same map object that thismap points at. So, naturally, when you change the contents of that object, both references (thismap and thatmap) see the changes.
Look at the APIs for Map.putAll(Map map) or a constructor that takes another Map as an arg. Either one will copy the contents of the map.
But be warned, that's just a shallow copy. The new Map gets its own keys and values, but those are references to the same objects that the original map had.
You can put/remove to one map without it affecting the other, but if you modify the contents of any of the keys (generally a bad idea anyway) or the values, then both Maps will see the changes. If you need to prevent that, you'll have to make copies of each of the key and value objects.