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 without doing it manually as I tried here:
public String[] getAllKeys() {
//index of string array "allkeys"
int j = 0;
String allkeys[] = new String[8];
//iterates through the bucketmap
for (int i = 0; i < buckets.length; i++) {
//checks wether bucket has a key and value
if (buckets[i] != null) {
//adds key to allkeys
allkeys[j] = buckets[i].key;
// counts up the allkeys index after adding key
j++;
//checks wether next has a key and value
if (buckets[i].next != null) {
//adds key to allkeys
allkeys[j] = buckets[i].next.key;
j++;
}
}
}
return allkeys;
}
Also how can I initialize the String[] allkeys using the version of j we get after the iteration is done as the index?
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<String,String> mp = new HashMap<String,String>();
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<String,String> 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;
}
See if this helps,
HashMap< String, String> map = new HashMap<>();
Set<String> keySet = map.keySet();
Iterator<String> iterator = keySet.iterator();
while(iterator.hasNext())
{
//iterate over keys
}
//or iterate over entryset
Iterator<Entry<String, String>> iterator2 = map.entrySet().iterator();
while(iterator2.hasNext())
{
Entry<String, String> next = iterator2.next();
//get key
next.getKey();
//get value
next.getValue();
}
With Java 8, I would suggest you to use Stream API.
It will allow you to iterate through the Map in a much more convenient approach:
public void iterateUsingStreamAPI(Map<String, Integer> map) {
map.entrySet().stream()
// ...
.forEach(e -> System.out.println(e.getKey() + ":" + e.getValue()));
}
Check out for more examples about iteration through maps in Java.