将一个地图与另一个索引地图存储在一起

Question

I want to store a whole Map in another Map with index. My code is as below:

HashMap<Integer, Map<String, String>> custMap = new HashMap<Integer, Map<String, String>>();
Map<String, String> mapCust = new HashMap<String, String>();

for (int i = 0; i < 10; i++) {
    mapCust.put("fname", fname);
    mapCust.put("lname", lname);
    mapCust.put("phone1", phone1);
    mapCust.put("phone2", phone2);

    custMap.put(i, mapCust);
}

Here I have total two Maps custMap and mapCust . So I want custMap as indexed Map with 10 sub maps of mapCust .

And here fname, lname, phone1 and phone2 are different for each Map mapCust .

But right now, I have all 10 sub Maps with same values like last value of mapCust in all 10 sub Maps.

Answer 1

HashMap will hold references, so you will have to create new objects for assigning to each keys.

HashMap<Integer, Map<String, String>> custMap = new HashMap<Integer, Map<String, String>>();

for (int i = 0; i < 10; i++) {
    Map<String, String> mapCust = new HashMap<String, String>(); // move this line inside the loop
    mapCust.put("fname", fname);
    mapCust.put("lname", lname);
    mapCust.put("phone1", phone1);
    mapCust.put("phone2", phone2);

    custMap.put(i, mapCust);
}

Answer 2

Create a new instance of HashMap everytime you iterate

HashMap<Integer, Map<String, String>> custMap = new HashMap<Integer,Map<String, String>>();

for (int i = 0; i < 10; i++) {
Map<String, String> mapCust = new HashMap<String, String>(); 
mapCust.put("fname", fname);
mapCust.put("lname", lname);
mapCust.put("phone1", phone1);
mapCust.put("phone2", phone2);
custMap.put(i, mapCust);
}

Earlier you were using the same instance of mapCust again and again.