Iterate Through a Hashmap

Iterate through a HashMap

Iterate through the entrySet() like so:

public static void printMap(Map mp) {
    Iterator it = mp.entrySet().iterator();
    while (it.hasNext()) {
        Map.Entry pair = (Map.Entry)it.next();
        System.out.println(pair.getKey() + " = " + pair.getValue());
        it.remove(); // avoids a ConcurrentModificationException
    }
}

Read more about Map.

How do I efficiently iterate over each entry in a Java Map?

Map<String, String> map = ...
for (Map.Entry<String, String> entry : map.entrySet()) {
    System.out.println(entry.getKey() + "/" + entry.getValue());
}

On Java 10+:

for (var entry : map.entrySet()) {
    System.out.println(entry.getKey() + "/" + entry.getValue());
}

How to iterate through a Map in java?

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)

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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;
}

Java: Iterate through a HashMap which is inside another HashMap

You could iterate the child map similar to how you've done the parent:

Iterator<Map.Entry<String, Map<String, String>>> parent = PropertyHolder.entrySet().iterator();
while (parent.hasNext()) {
    Map.Entry<String, Map<String, String>> parentPair = parent.next();
    System.out.println("parentPair.getKey() :   " + parentPair.getKey() + " parentPair.getValue()  :  " + parentPair.getValue());

    Iterator<Map.Entry<String, String>> child = (parentPair.getValue()).entrySet().iterator();
    while (child.hasNext()) {
        Map.Entry childPair = child.next();
        System.out.println("childPair.getKey() :   " + childPair.getKey() + " childPair.getValue()  :  " + childPair.getValue());

        child.remove(); // avoids a ConcurrentModificationException
    }

}

I've presumed you want to call .remove() on the child map, which will lead to a ConcurrentModificationException if done while looping the entrySet - it looks as though you discovered this already.

I've also swapped out your use of casting with strongly-typed generics as suggested in the comments.

Iterating through a HashMap in a For Each style

Use the values collection

for(GameObject gameObject : character.values()) { 
    if(gameObject instanceof Stat) { }
}

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