1 files changed, 110 insertions, 0 deletions
diff --git a/src/main/java/bjc/esodata/Multimap.java b/src/main/java/bjc/esodata/Multimap.java
new file mode 100644
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+++ b/src/main/java/bjc/esodata/Multimap.java
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+package bjc.esodata;
+
+import java.util.*;
+
+import bjc.data.*;
+
+/**
+ * A map that has support for multiple values for a given key.
+ *
+ * Whenever you give another value for a key, that is then returned for that key. About the only
+ * somewhat complex thing, is that, if you add the same key-value pair multiple times, it will only
+ * show up once. However, you will have to remove that pair as many times as you added it.
+ *
+ * @author Ben Culkin
+ */
+public class Multimap<KeyType, ValueType> {
+	private Map<KeyType, ThresholdSet<ValueType>> backing;
+
+	/**
+	 * Create a new empty multimap.
+	 */
+	public Multimap() {
+		backing = new HashMap<>();
+	}
+
+	/**
+	 * Add a key-value mapping to the map.
+	 *
+	 * @param key
+	 * 	The key to store the value under.
+	 *
+	 * @param value
+	 * 	The value to store.
+	 */
+	public void add(KeyType key, ValueType value) {
+		ThresholdSet<ValueType> container = backing.computeIfAbsent(key,
+				(k) -> new ThresholdSet());
+
+		container.add(value);
+	}
+
+	/**
+	 * Delete a particular key-value mapping from the map.
+	 *
+	 * @param key
+	 * 	The key of the mapping to remove.
+	 *
+	 * @param value
+	 * 	The value of the mapping to remove.
+	 */
+	public void remove(KeyType key, ValueType value) {
+		// We have no values for that key; bail.
+		if (!backing.containsKey(key)) return;
+
+		backing.get(key).remove(value);
+	}
+
+	/**
+	 * Delete all of the values associated with a particular key.
+	 *
+	 * @param key
+	 * 	The key to remove values for.
+	 */
+	public void remove(KeyType key) {
+		backing.remove(key);
+	}
+
+	/**
+	 * Get a set containing all of the values that are recorded for that key.
+	 *
+	 * @param key
+	 * 	The key to look up values for.
+	 *
+	 * @return A set containing all of the values that have been mapped to that key.
+	 */
+	public Set<ValueType> get(KeyType key) {
+		if (!backing.containsKey(key)) return new HashSet<>();
+
+		return backing.get(key).values();
+	}
+
+	/**
+	 * Check if there is at least one value mapped to the given key.
+	 *
+	 * @param key
+	 * 	The key to check for mappings for.
+	 * 
+	 * @return Whether or not there is at least one value mapped to the key.
+	 */
+	public boolean contains(KeyType key) {
+		return backing.containsKey(key);
+	}
+
+	/**
+	 * Check if there is at least one instance of a particular key-value mapping.
+	 *
+	 * @param key
+	 * 	The key to check for mappings for.
+	 *
+	 * @param value
+	 * 	The value to check for mappings for.
+	 * 
+	 * @return Whether or not there is at least one instance of the given key-value mapping.
+	 */
+	public boolean contains(KeyType key, ValueType value) {
+		if (!backing.containsKey(key)) return false;
+
+		return backing.get(key).contains(value) > 0;
+	}
+}