How to iterate through a Map in java?

Question

I need to iterate through a BucketMap and get all keys but how do I get to something like buckets[i].next.next.next.key for instance witho

Answer 1

For basic utilisation, the HashMap is the best, I've put how to iterate over it, easier than using an iterator :

public static void main (String[] args) {
    //a map with key type : String, value type : String
    Map mp = new HashMap();
    mp.put("John","Math");    mp.put("Jack","Math");    map.put("Jeff","History");

    //3 differents ways to iterate over the map
    for (String key : mp.keySet()){
        //iterate over keys
        System.out.println(key+" "+mp.get(key));
    }

    for (String value : mp.values()){
        //iterate over values
        System.out.println(value);
    }

    for (Entry pair : mp.entrySet()){
        //iterate over the pairs
        System.out.println(pair.getKey()+" "+pair.getValue());
    }
}

A quick explanation :

for (String name : mp.keySet()){
        //Do Something
}

means : "For all string from the keys of the map, we'll do something, and at each iteration we will call the key 'name' (it can be whatever you want, it's a variable)

---

Here we go :

public String[] getAllKeys(){ 
    int i = 0;
    String allkeys[] = new String[buckets.length];
    KeyValue val = buckets[i];

    //Look at the first one          
    if(val != null) {             
        allkeys[i] = val.key; 
        i++;
    }

    //Iterate until there is no next
    while(val.next != null){
        allkeys[i] = val.next.key;
        val = val.next;
        i++;
    }

    return allkeys;
}