#949 Created TimedCounter + implement it in TempbanManager

src/main/java/fr/xephi/authme/util/ExpiringMap.java

@@ -24,7 +24,7 @@ import java.util.concurrent.TimeUnit;
  */
 public class ExpiringMap<K, V> {
 
-    private final Map<K, ExpiringEntry<V>> entries = new ConcurrentHashMap<>();
+    protected final Map<K, ExpiringEntry<V>> entries = new ConcurrentHashMap<>();
     private long expirationMillis;
 
     /**
@@ -88,12 +88,23 @@ public class ExpiringMap<K, V> {
         this.expirationMillis = unit.toMillis(duration);
     }
 
+    /**
+     * Returns whether this map is empty. This reflects the state of the
+     * internal map, which may contain expired entries only. The result
+     * may change after running {@link #removeExpiredEntries()}.
+     *
+     * @return true if map is really empty, false otherwise
+     */
+    public boolean isEmpty() {
+        return entries.isEmpty();
+    }
+
     /**
      * Class holding a value paired with an expiration timestamp.
      *
      * @param <V> the value type
      */
-    private static final class ExpiringEntry<V> {
+    protected static final class ExpiringEntry<V> {
 
         private final V value;
         private final long expiration;

src/main/java/fr/xephi/authme/util/TimedCounter.java

@@ -0,0 +1,50 @@
+package fr.xephi.authme.util;
+
+import java.util.Objects;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Keeps a count per key which expires after a configurable amount of time.
+ * <p>
+ * Once the expiration of an entry has been reached, the counter resets
+ * to 0. The counter returns 0 rather than {@code null} for any given key.
+ */
+public class TimedCounter<K> extends ExpiringMap<K, Integer> {
+
+    /**
+     * Constructor.
+     *
+     * @param duration the duration of time after which entries expire
+     * @param unit the time unit in which {@code duration} is expressed
+     */
+    public TimedCounter(long duration, TimeUnit unit) {
+        super(duration, unit);
+    }
+
+    @Override
+    public Integer get(K key) {
+        Integer value = super.get(key);
+        return value == null ? 0 : value;
+    }
+
+    /**
+     * Increments the value stored for the provided key.
+     *
+     * @param key the key to increment the counter for
+     */
+    public void increment(K key) {
+        put(key, get(key) + 1);
+    }
+
+    /**
+     * Calculates the total of all non-expired entries in this counter.
+     *
+     * @return the total of all valid entries
+     */
+    public int total() {
+        return entries.values().stream()
+            .map(ExpiringEntry::getValue)
+            .filter(Objects::nonNull)
+            .reduce(0, Integer::sum);
+    }
+}