HCOLL-136 HCOLL-137 HCOLL-164 Extracted ChronicleHash abstraction and updated ChronicleMap docs

src/main/java/net/openhft/chronicle/map/ChronicleMap.java

@@ -16,24 +16,103 @@
 
 package net.openhft.chronicle.map;
 
+import net.openhft.chronicle.ChronicleHash;
+import net.openhft.chronicle.map.serialization.BytesReader;
+import net.openhft.lang.io.Bytes;
+import net.openhft.lang.io.serialization.BytesMarshaller;
+import net.openhft.lang.io.serialization.ObjectFactory;
+import net.openhft.lang.model.Byteable;
+
 import java.io.Closeable;
 import java.io.File;
+import java.io.IOException;
+import java.util.Map;
 import java.util.concurrent.ConcurrentMap;
 
-public interface ChronicleMap<K, V> extends ConcurrentMap<K, V>, Closeable {
+/**
+ * Extension of {@link ConcurrentMap} interface, stores the data off-heap.
+ *
+ * <p>For information on
+ * <ul>
+ *     <li>how to construct a {@code ChronicleMap}</li>
+ *     <li>{@code ChronicleMap} flavors and properties</li>
+ *     <li>available configurations</li>
+ * </ul>
+ * see {@link ChronicleMapBuilder} documentation.
+ *
+ * <p>Functionally this interface defines some methods supporting garbage-free off-heap programming:
+ * {@link #getUsing(Object, Object)}, {@link #acquireUsing(Object, Object)}.
+ *
+ * <p>Note that {@code ChronicleMap} extends {@link Closeable}, don't forget
+ * to {@linkplain #close() close} map when it is no longer needed.
+ *
+ * @param <K> the map key type
+ * @param <V> the map value type
+ */
+public interface ChronicleMap<K, V> extends ConcurrentMap<K, V>, ChronicleHash {
     /**
-     * @return size as a long.
-     * @see java.util.Map size()
+     * Returns the number of entries in this map.
+     *
+     * @return number of entries in this map
+     * @see Map#size()
      */
     long longSize();
 
     /**
-     * Get a value for a key if available.  If the value is Byteable, it will be assigned to
-     * reference the value, instead of copying the data for zero copy access to the collection.
+     * Returns the value to which the specified key is mapped, or {@code null} if this map contains
+     * no mapping for the key.
      *
-     * @param key   to lookup.
-     * @param value to reuse if possible. If null, a new object will be created.
-     * @return value found or null if not.
+     * <p>If the specified key if absent in the map, {@linkplain
+     * ChronicleMapBuilder#defaultValue(Object) default value} is taken or {@linkplain
+     * ChronicleMapBuilder#defaultValueProvider(DefaultValueProvider) default value provider}
+     * is called (depending on what was configured last in {@code ChronicleMapBuilder}).
+     * If it results to something different from {@code null}, this object is put to this map for
+     * the specified key, and then returned from this {@code get()} call. Otherwise, if default
+     * value is {@code null} and default value provider returns {@code null}, the map remains
+     * unchanged and {@code null} is returned.
+     *
+     * <p>If the value class allows reusing, particularly if it is a {@link Byteable} subclass,
+     * consider {@link #getUsing(Object, Object)} method instead of this to reduce garbage creation.
+     *
+     * @param key the key whose associated value is to be returned
+     * @return the value to which the specified key is mapped after this method call,
+     * or {@code null} if no value is mapped
+     * @see #getUsing(Object, Object)
+     */
+    @Override
+    V get(Object key);
+
+    /**
+     * Returns the value to which the specified key is mapped, read to the provided {@code value}
+     * object, if possible, or returns {@code null}, if this map contains no mapping for the key.
+     *
+     * <p>If the specified key is present in the map, the value data is read to the provided
+     * {@code value} object via value marshaller's {@link BytesMarshaller#read(Bytes, Object)
+     * read(Bytes, value)} or value reader's {@link BytesReader#read(Bytes, long, Object)
+     * read(Bytes, size, value)} method, depending on what deserialization strategy is configured
+     * on this map builder. If the value deserializer is able to reuse the given {@code value}
+     * object, calling this method instead of {@link #get(Object)} could help to reduce garbage
+     * creation.
+     *
+     * <p>The provided {@code value} object is allowed to be {@code null}, in this case
+     * {@code map.getUsing(key, null)} call is semantically equivalent to simple
+     * {@code map.get(key)} call.
+     *
+     * <p>If the specified key if absent in the map, {@linkplain
+     * ChronicleMapBuilder#defaultValue(Object) default value} is taken or {@linkplain
+     * ChronicleMapBuilder#defaultValueProvider(DefaultValueProvider) default value provider}
+     * is called. If it results to something different from {@code null}, this object is put
+     * to this map for the specified key, and then a new value is returned from this
+     * {@code getUsing()} call. Otherwise, if default value is {@code null} and default value
+     * provider, if specified, returns {@code null}, the map remains unchanged and {@code null}
+     * is returned. The provided {@code value} is untouched anyway in this case.
+     *
+     * @param key   the key whose associated value is to be returned
+     * @param value the object to read value data in, if possible
+     * @return the value mapped to the specified key after this method call, or {@code null} if no
+     * value is mapped
+     * @see #get(Object)
+     * @see ChronicleMapBuilder#valueMarshallerAndFactory(BytesMarshaller, ObjectFactory)
      */
     V getUsing(K key, V value);
 
@@ -41,15 +120,10 @@ public interface ChronicleMap<K, V> extends ConcurrentMap<K, V>, Closeable {
      * Acquire a value for a key, creating if absent. If the value is Byteable, it will be assigned
      * to reference the value, instead of copying the data.
      *
-     * @param key   to lookup.
+     * @param key   the key whose associated value is to be returned
      * @param value to reuse if possible. If null, a new object will be created.
      * @return value created or found.
      */
     V acquireUsing(K key, V value);
 
-    /**
-     * @return The file or directory for this ChronicleMap
-     */
-    File file();
-
 }