Databases
StackOverflow2013
Postsdbo
POJava HashMap nested generics with wildcards
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POJava HashMap nested generics with wildcards
    primarykey
    data
    text
    <p>I'm trying to make a hashmap of hashmap values containing hashsets of different subclasses of a custom class, like so:</p> <pre><code>HashMap&lt;String, Hashmap&lt;String, HashSet&lt;? extends AttackCard&gt;&gt;&gt; superMap </code></pre> <p><code>AttackCard</code> has subclasses such as: <code>Mage</code>, <code>Assassin</code>, <code>Fighter</code>. Each HashMap in the superMap will only ever have HashSets containing a single subclass of <code>AttackCard</code>.</p> <p>When I try putting a</p> <pre><code>HashMap&lt;String, HashSet&lt;Assassin&gt;&gt; </code></pre> <p>into superMap, I get a compiler error: <a href="https://i.stack.imgur.com/jnp5O.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/jnp5O.png" alt="comiler error"></a></p> <p>below is the code where the error occurs:</p> <pre><code>public class CardPool { private HashMap&lt;String, HashMap&lt;String, HashSet&lt;? extends AttackCard&gt;&gt;&gt; attackPool = new HashMap&lt;&gt;(); private ArrayList&lt;AuxiliaryCard&gt; auxiliaryPool; public CardPool() { (line 24)this.attackPool.put("assassins", new AssassinPool().get()); /* this.attackPool.put("fighters", new Fighter().getPool()); this.attackPool.put("mages", new Mage().getPool()); this.attackPool.put("marksmen", new Marksman().getPool()); this.attackPool.put("supports", new Support().getPool()); this.attackPool.put("tanks", new Tank().getPool()); */ this.auxiliaryPool = new ArrayList&lt;&gt;(new AuxiliaryCard().getPool()); } </code></pre> <p>And here is a snippet of the AssassinPool get-method:</p> <pre><code>private HashMap&lt;String, HashSet&lt;Assassin&gt;&gt; pool = new HashMap&lt;&gt;(); public HashMap&lt;String, HashSet&lt;Assassin&gt;&gt; get() { return pool; } </code></pre> <p>I'd like to comment that I could easily solve my problem and have a wonderfully working program by making all the AttackCardPools, such as AssassinPool, return and contain HashSets of AttackCard instead of their respective subclass. I'm trying to understand this compilation error, however :)</p> <pre><code>compilation error at line 24: error: no suitable method found for `put(String, HashMap&lt;String,HashSet&lt;Assassin&gt;&gt;&gt;` this.attackPool.put("assassins", new AssassinPool(). get()); method HashMap.putp.(String, HashMap&lt;String,HashSet&lt;? extends AttackCard&gt;&gt;&gt;` is not applicable (actual argument `HashMap&lt;String, HashSet&lt;Assassin&gt;&gt;` cannot be converted to `HashMap&lt;String, HashSet&lt;? extends AttackCard&gt;&gt;` by method invocation conversion) </code></pre>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USrafid059
    1. USuser2651804
    plurals
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    1. PL
      singulars
      1. LTLinked
    2. PL
      singulars
      1. LTLinked
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POJava HashMap nested generics with wildcards
      1. USGab
      1. VTFavorite
    2. VO
      singulars
      1. POJava HashMap nested generics with wildcards
      1. USRohit Jain
      1. VTFavorite
    3. VO
      singulars
      1. POJava HashMap nested generics with wildcards
      1. This table or related slice is empty.
      1. VTUpMod
    1. COPost the exception stack trace here as text and not an image or a link to an image.
      singulars
      1. POJava HashMap nested generics with wildcards
      1. USSudoRahul
    2. CO`a hashmap of hashmaps containing hashsets` --> too deep, you should try to write a custom object that handles values of your top-map.
      singulars
      1. POJava HashMap nested generics with wildcards
      1. USsp00m
    3. COcompilation error at line 24: error: no suitable method found for put(String, HashMap<String,HashSet<Assassin>>> this.attackPool.put("assassins", new AssassinPool(). get()); method HashMap.putp.(String, HashMap<String,HashSet<? extends AttackCard>>> is not applicable (actual argument HashMap<String, HashSet<Assassin>> cannot be converted to HashMap<String, HashSet<? extends AttackCard>> by method invocation conversion)
      singulars
      1. POJava HashMap nested generics with wildcards
      1. USuser2651804
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload