Why is my nested hashmap setting all the values to the same thing?

Question

This is my first foray into java, and I am having trouble understanding how maps work. I have a for loop which appends maps of information into another map. However when I look at the outermost map it contains the correct number of sub-maps, however they all conatin the same information, even though I originally put different information in them... does anyone know why?

Thanks,

Lemiant

Below I have included my code and the System.out.print output:

Code:

Map continents = new HashMap();
Map continentData = new HashMap();
int lastContinent = -1;


//Accumulate Continent data
for(Country currCountry : countries){
    continentData.clear();
    int currContinent = currCountry.getContinent();

    continentData.put("P", 0);
    continentData.put("E", 1);
    continentData.put("O", 2);
    continentData.put("Bonus",currContinent);

    if(currContinent != lastContinent){
        continents.put(currContinent, continentData);
        System.out.println("add");
        System.out.println(continentData);
    }

    lastContinent = currContinent;
}

System.out.println(continents.toString());

Result:

add
{E=1, P=0, O=2, Bonus=0}
add
{E=1, P=0, O=2, Bonus=1}
add
{E=1, P=0, O=2, Bonus=2}
add
{E=1, P=0, O=2, Bonus=3}
add
{E=1, P=0, O=2, Bonus=4}
add
{E=1, P=0, O=2, Bonus=5}
{0={E=1, P=0, O=2, Bonus=5}, 1={E=1, P=0, O=2, Bonus=5}, 2={E=1, P=0, O=2, Bonus=5}, 3={E=1, P=0, O=2, Bonus=5}, 4={E=1, P=0, O=2, Bonus=5}, 5={E=1, P=0, O=2, Bonus=5}}

Answer 1

You need to move Map continentData = new HashMap(); inside your for loop so that a separate map is created on each pass. Right now you're just updating the same map over and over.

Answer 2

You are using the same instance of continentData for all the maps. You must instantiate a new Map for it in each loop interation.

for(Country currCountry : countries){
    //continentData.clear();
    Map continentData = new HashMap();
    int currContinent = currCountry.getContinent();