X-Git-Url: https://git.opendaylight.org/gerrit/gitweb?a=blobdiff_plain;f=yang%2Fyang-data-api%2Fsrc%2Fmain%2Fjava%2Forg%2Fopendaylight%2Fyangtools%2Fyang%2Fdata%2Fapi%2FYangInstanceIdentifier.java;h=6f2c49cfa3d28a8d8d8f54c10c0e3a56fdfaf135;hb=41ad3de3b8ada6aaa77fab41f7a340d268055742;hp=53b8343cd18760a5977a2681c879672c10dcbfde;hpb=2832d604e4de5aa8136e65baca528a9be9154557;p=yangtools.git

diff --git a/yang/yang-data-api/src/main/java/org/opendaylight/yangtools/yang/data/api/YangInstanceIdentifier.java b/yang/yang-data-api/src/main/java/org/opendaylight/yangtools/yang/data/api/YangInstanceIdentifier.java
index 53b8343cd1..6f2c49cfa3 100644
--- a/yang/yang-data-api/src/main/java/org/opendaylight/yangtools/yang/data/api/YangInstanceIdentifier.java
+++ b/yang/yang-data-api/src/main/java/org/opendaylight/yangtools/yang/data/api/YangInstanceIdentifier.java
@@ -1,39 +1,44 @@
 /*
  * Copyright (c) 2014 Cisco Systems, Inc. and others. All rights reserved.
+ *
  * This program and the accompanying materials are made available under the
  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
  * and is available at http://www.eclipse.org/legal/epl-v10.html
  */
 package org.opendaylight.yangtools.yang.data.api;
 
-import com.google.common.base.Optional;
-import com.google.common.base.Preconditions;
-import com.google.common.collect.ImmutableList;
-import com.google.common.collect.ImmutableMap;
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Verify.verify;
+import static java.util.Objects.requireNonNull;
+
+import com.google.common.annotations.Beta;
+import com.google.common.cache.CacheBuilder;
+import com.google.common.cache.CacheLoader;
+import com.google.common.cache.LoadingCache;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Iterables;
-import com.google.common.collect.Lists;
-import java.io.IOException;
-import java.io.ObjectInputStream;
-import java.io.ObjectOutputStream;
-import java.io.ObjectStreamException;
+import com.google.common.collect.Sets;
 import java.io.Serializable;
 import java.lang.reflect.Array;
-import java.lang.reflect.Field;
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.Collections;
+import java.util.Collection;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
 import org.opendaylight.yangtools.concepts.Builder;
 import org.opendaylight.yangtools.concepts.Immutable;
 import org.opendaylight.yangtools.concepts.Path;
 import org.opendaylight.yangtools.util.HashCodeBuilder;
+import org.opendaylight.yangtools.util.ImmutableOffsetMap;
+import org.opendaylight.yangtools.util.SharedSingletonMap;
 import org.opendaylight.yangtools.yang.common.QName;
 import org.opendaylight.yangtools.yang.common.QNameModule;
 import org.opendaylight.yangtools.yang.data.api.schema.LeafSetEntryNode;
@@ -46,16 +51,18 @@ import org.opendaylight.yangtools.yang.data.api.schema.LeafSetEntryNode;
  * which conceptually is XPath expression minimized to uniquely identify element
  * in data tree which conforms to constraints maintained by YANG Model,
  * effectively this makes Instance Identifier a path to element in data tree.
+ *
  * <p>
  * Constraints put in YANG specification on instance-identifier allowed it to be
  * effectively represented in Java and it's evaluation does not require
  * full-blown XPath processor.
+ *
  * <p>
  * <h3>Path Arguments</h3>
  * Path to the node represented in instance identifier consists of
  * {@link PathArgument} which carries necessary information to uniquely identify
  * node on particular level in the subtree.
- * <p>
+ *
  * <ul>
  * <li>{@link NodeIdentifier} - Identifier of node, which has cardinality
  * <code>0..1</code> in particular subtree in data tree.</li>
@@ -67,73 +74,73 @@ import org.opendaylight.yangtools.yang.data.api.schema.LeafSetEntryNode;
  * <code>augmentation</code> node.</li>
  * </ul>
  *
- *
  * @see <a href="http://tools.ietf.org/html/rfc6020#section-9.13">RFC6020</a>
  */
-public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier>, Immutable, Serializable {
+public abstract class YangInstanceIdentifier implements Path<YangInstanceIdentifier>, Immutable, Serializable {
     /**
      * An empty {@link YangInstanceIdentifier}. It corresponds to the path of the conceptual
      * root of the YANG namespace.
      */
-    public static final YangInstanceIdentifier EMPTY = trustedCreate(Collections.<PathArgument>emptyList());
-    @SuppressWarnings("rawtypes")
-    private static final AtomicReferenceFieldUpdater<YangInstanceIdentifier, ImmutableList> LEGACYPATH_UPDATER =
-            AtomicReferenceFieldUpdater.newUpdater(YangInstanceIdentifier.class, ImmutableList.class, "legacyPath");
+    public static final YangInstanceIdentifier EMPTY = FixedYangInstanceIdentifier.EMPTY_INSTANCE;
+
     private static final AtomicReferenceFieldUpdater<YangInstanceIdentifier, String> TOSTRINGCACHE_UPDATER =
             AtomicReferenceFieldUpdater.newUpdater(YangInstanceIdentifier.class, String.class, "toStringCache");
-    private static final Field PATHARGUMENTS_FIELD;
+    private static final long serialVersionUID = 4L;
 
-    private static final long serialVersionUID = 3L;
-    private final transient Iterable<PathArgument> pathArguments;
     private final int hash;
-
-    private volatile ImmutableList<PathArgument> legacyPath = null;
     private transient volatile String toStringCache = null;
 
-    static {
-        final Field f;
-        try {
-            f = YangInstanceIdentifier.class.getDeclaredField("pathArguments");
-        } catch (NoSuchFieldException | SecurityException e) {
-            throw new ExceptionInInitializerError(e);
-        }
-        f.setAccessible(true);
-
-        PATHARGUMENTS_FIELD = f;
+    // Package-private to prevent outside subclassing
+    YangInstanceIdentifier(final int hash) {
+        this.hash = hash;
     }
 
-    private ImmutableList<PathArgument> getLegacyPath() {
-        // Temporary variable saves a volatile read
-        ImmutableList<PathArgument> ret = legacyPath;
-        if (ret == null) {
-            // We could have used a synchronized block, but the window is quite
-            // small and worst that can happen is duplicate object construction.
-            ret = ImmutableList.copyOf(pathArguments);
-            LEGACYPATH_UPDATER.lazySet(this, ret);
-        }
+    @Nonnull abstract YangInstanceIdentifier createRelativeIdentifier(int skipFromRoot);
 
-        return ret;
-    }
+    @Nonnull abstract Collection<PathArgument> tryPathArguments();
+
+    @Nonnull abstract Collection<PathArgument> tryReversePathArguments();
 
     /**
-     * Returns a list of path arguments.
+     * Check if this instance identifier has empty path arguments, e.g. it is
+     * empty and corresponds to {@link #EMPTY}.
      *
-     * @deprecated Use {@link #getPathArguments()} instead.
-     * @return Immutable list of path arguments.
+     * @return True if this instance identifier is empty, false otherwise.
      */
-    @Deprecated
-    public List<PathArgument> getPath() {
-        return getLegacyPath();
-    }
+    public abstract boolean isEmpty();
+
+    /**
+     * Return an optimized version of this identifier, useful when the identifier
+     * will be used very frequently.
+     *
+     * @return A optimized equivalent instance.
+     */
+    @Beta
+    public abstract YangInstanceIdentifier toOptimized();
+
+    /**
+     * Return the conceptual parent {@link YangInstanceIdentifier}, which has
+     * one item less in {@link #getPathArguments()}.
+     *
+     * @return Parent {@link YangInstanceIdentifier}, or null if this object is {@link #EMPTY}.
+     */
+    @Nullable public abstract YangInstanceIdentifier getParent();
+
+    /**
+     * Return the ancestor {@link YangInstanceIdentifier} with a particular depth, e.g. number of path arguments.
+     *
+     * @param depth Ancestor depth
+     * @return Ancestor {@link YangInstanceIdentifier}
+     * @throws IllegalArgumentException if the specified depth is negative or is greater than the depth of this object.
+     */
+    @Nonnull public abstract YangInstanceIdentifier getAncestor(int depth);
 
     /**
      * Returns an ordered iteration of path arguments.
      *
      * @return Immutable iteration of path arguments.
      */
-    public Iterable<PathArgument> getPathArguments() {
-        return pathArguments;
-    }
+    public abstract List<PathArgument> getPathArguments();
 
     /**
      * Returns an iterable of path arguments in reverse order. This is useful
@@ -141,9 +148,7 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
      *
      * @return Immutable iterable of path arguments in reverse order.
      */
-    public Iterable<PathArgument> getReversePathArguments() {
-        return getLegacyPath().reverse();
-    }
+    public abstract List<PathArgument> getReversePathArguments();
 
     /**
      * Returns the last PathArgument. This is equivalent of iterating
@@ -151,30 +156,19 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
      *
      * @return The last past argument, or null if there are no PathArguments.
      */
-    public PathArgument getLastPathArgument() {
-        return Iterables.getFirst(getReversePathArguments(), null);
-    }
+    public abstract PathArgument getLastPathArgument();
 
-    private YangInstanceIdentifier(final Iterable<PathArgument> path, final int hash) {
-        this.pathArguments = Preconditions.checkNotNull(path, "path must not be null.");
-        this.hash = hash;
-    }
+    public static YangInstanceIdentifier create(final Iterable<? extends PathArgument> path) {
+        if (Iterables.isEmpty(path)) {
+            return EMPTY;
+        }
 
-    private static YangInstanceIdentifier trustedCreate(final Iterable<PathArgument> path) {
         final HashCodeBuilder<PathArgument> hash = new HashCodeBuilder<>();
         for (PathArgument a : path) {
             hash.addArgument(a);
         }
 
-        return new YangInstanceIdentifier(path, hash.build());
-    }
-
-    public static YangInstanceIdentifier create(final Iterable<? extends PathArgument> path) {
-        if (Iterables.isEmpty(path)) {
-            return EMPTY;
-        }
-
-        return trustedCreate(ImmutableList.copyOf(path));
+        return FixedYangInstanceIdentifier.create(path, hash.build());
     }
 
     public static YangInstanceIdentifier create(final PathArgument... path) {
@@ -182,16 +176,8 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         return create(Arrays.asList(path));
     }
 
-    @Override
-    public int hashCode() {
-        /*
-         * The caching is safe, since the object contract requires
-         * immutability of the object and all objects referenced from this
-         * object.
-         * Used lists, maps are immutable. Path Arguments (elements) are also
-         * immutable, since the PathArgument contract requires immutability.
-         */
-        return hash;
+    boolean pathArgumentsEqual(final YangInstanceIdentifier other) {
+        return Iterables.elementsEqual(getPathArguments(), other.getPathArguments());
     }
 
     @Override
@@ -199,38 +185,35 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         if (this == obj) {
             return true;
         }
-        if (obj == null) {
-            return false;
-        }
-        if (getClass() != obj.getClass()) {
+        if (!(obj instanceof YangInstanceIdentifier)) {
             return false;
         }
         YangInstanceIdentifier other = (YangInstanceIdentifier) obj;
         if (this.hashCode() != obj.hashCode()) {
             return false;
         }
-        return Iterables.elementsEqual(pathArguments, other.pathArguments);
+
+        return pathArgumentsEqual(other);
     }
 
     /**
-     * Constructs a new Instance Identifier with new {@link NodeIdentifier} added to the end of path arguments
+     * Constructs a new Instance Identifier with new {@link NodeIdentifier} added to the end of path arguments.
      *
      * @param name QName of {@link NodeIdentifier}
      * @return Instance Identifier with additional path argument added to the end.
      */
-    public YangInstanceIdentifier node(final QName name) {
+    public final YangInstanceIdentifier node(final QName name) {
         return node(new NodeIdentifier(name));
     }
 
     /**
-     *
-     * Constructs a new Instance Identifier with new {@link PathArgument} added to the end of path arguments
+     * Constructs a new Instance Identifier with new {@link PathArgument} added to the end of path arguments.
      *
      * @param arg Path argument which should be added to the end
      * @return Instance Identifier with additional path argument added to the end.
      */
-    public YangInstanceIdentifier node(final PathArgument arg) {
-        return new YangInstanceIdentifier(Iterables.concat(pathArguments, Collections.singleton(arg)), HashCodeBuilder.nextHashCode(hash, arg));
+    public final YangInstanceIdentifier node(final PathArgument arg) {
+        return new StackedYangInstanceIdentifier(this, arg, HashCodeBuilder.nextHashCode(hash, arg));
     }
 
     /**
@@ -243,14 +226,21 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
      *         the specified parent is not in fact an ancestor of this object.
      */
     public Optional<YangInstanceIdentifier> relativeTo(final YangInstanceIdentifier ancestor) {
-        final Iterator<?> lit = pathArguments.iterator();
-        final Iterator<?> oit = ancestor.pathArguments.iterator();
+        if (this == ancestor) {
+            return Optional.of(EMPTY);
+        }
+        if (ancestor.isEmpty()) {
+            return Optional.of(this);
+        }
+
+        final Iterator<PathArgument> lit = getPathArguments().iterator();
+        final Iterator<PathArgument> oit = ancestor.getPathArguments().iterator();
         int common = 0;
 
         while (oit.hasNext()) {
             // Ancestor is not really an ancestor
             if (!lit.hasNext() || !lit.next().equals(oit.next())) {
-                return Optional.absent();
+                return Optional.empty();
             }
 
             ++common;
@@ -262,7 +252,72 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         if (!lit.hasNext()) {
             return Optional.of(EMPTY);
         }
-        return Optional.of(trustedCreate(Iterables.skip(pathArguments, common)));
+
+        return Optional.of(createRelativeIdentifier(common));
+    }
+
+    @Override
+    public final boolean contains(@Nonnull final YangInstanceIdentifier other) {
+        if (this == other) {
+            return true;
+        }
+
+        checkArgument(other != null, "other should not be null");
+        final Iterator<PathArgument> lit = getPathArguments().iterator();
+        final Iterator<PathArgument> oit = other.getPathArguments().iterator();
+
+        while (lit.hasNext()) {
+            if (!oit.hasNext()) {
+                return false;
+            }
+
+            if (!lit.next().equals(oit.next())) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    @Override
+    public final String toString() {
+        /*
+         * The toStringCache is safe, since the object contract requires
+         * immutability of the object and all objects referenced from this
+         * object.
+         * Used lists, maps are immutable. Path Arguments (elements) are also
+         * immutable, since the PathArgument contract requires immutability.
+         * The cache is thread-safe - if multiple computations occurs at the
+         * same time, cache will be overwritten with same result.
+         */
+        String ret = toStringCache;
+        if (ret == null) {
+            final StringBuilder builder = new StringBuilder("/");
+            PathArgument prev = null;
+            for (PathArgument argument : getPathArguments()) {
+                if (prev != null) {
+                    builder.append('/');
+                }
+                builder.append(argument.toRelativeString(prev));
+                prev = argument;
+            }
+
+            ret = builder.toString();
+            TOSTRINGCACHE_UPDATER.lazySet(this, ret);
+        }
+        return ret;
+    }
+
+    @Override
+    public final int hashCode() {
+        /*
+         * The caching is safe, since the object contract requires
+         * immutability of the object and all objects referenced from this
+         * object.
+         * Used lists, maps are immutable. Path Arguments (elements) are also
+         * immutable, since the PathArgument contract requires immutability.
+         */
+        return hash;
     }
 
     private static int hashCode(final Object value) {
@@ -270,7 +325,7 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
             return 0;
         }
 
-        if (value.getClass().equals(byte[].class)) {
+        if (byte[].class.equals(value.getClass())) {
             return Arrays.hashCode((byte[]) value);
         }
 
@@ -290,8 +345,8 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
     // Static factories & helpers
 
     /**
-     *
-     * Returns a new InstanceIdentifier with only one path argument of type {@link NodeIdentifier} with supplied QName
+     * Returns a new InstanceIdentifier with only one path argument of type {@link NodeIdentifier} with supplied
+     * QName.
      *
      * @param name QName of first node identifier
      * @return Instance Identifier with only one path argument of type {@link NodeIdentifier}
@@ -301,38 +356,38 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
     }
 
     /**
-     *
      * Returns new builder for InstanceIdentifier with empty path arguments.
      *
      * @return new builder for InstanceIdentifier with empty path arguments.
      */
     public static InstanceIdentifierBuilder builder() {
-        return new BuilderImpl();
+        return new YangInstanceIdentifierBuilder();
     }
 
     /**
-     *
      * Returns new builder for InstanceIdentifier with path arguments copied from original instance identifier.
      *
-     * @param origin Instace Identifier from which path arguments are copied.
+     * @param origin InstanceIdentifier from which path arguments are copied.
      * @return new builder for InstanceIdentifier with path arguments copied from original instance identifier.
      */
     public static InstanceIdentifierBuilder builder(final YangInstanceIdentifier origin) {
-        return new BuilderImpl(origin.getPathArguments(), origin.hashCode());
+        return new YangInstanceIdentifierBuilder(origin.getPathArguments(), origin.hashCode());
     }
 
     /**
-     * Path argument / component of InstanceIdentifier
-     *
+     * Path argument / component of InstanceIdentifier.
      * Path argument uniquely identifies node in data tree on particular
      * level.
+     *
      * <p>
      * This interface itself is used as common parent for actual
      * path arguments types and should not be implemented by user code.
+     *
      * <p>
      * Path arguments SHOULD contain only minimum of information
      * required to uniquely identify node on particular subtree level.
      *
+     * <p>
      * For actual path arguments types see:
      * <ul>
      * <li>{@link NodeIdentifier} - Identifier of container or leaf
@@ -346,6 +401,7 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
          * If applicable returns unique QName of data node as defined in YANG
          * Schema.
          *
+         * <p>
          * This method may return null, if the corresponding schema node, does
          * not have QName associated, such as in cases of augmentations.
          *
@@ -365,15 +421,14 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         String toRelativeString(PathArgument previous);
     }
 
-    private static abstract class AbstractPathArgument implements PathArgument {
-        private static final AtomicReferenceFieldUpdater<AbstractPathArgument, Integer> HASH_UPDATER =
-                AtomicReferenceFieldUpdater.newUpdater(AbstractPathArgument.class, Integer.class, "hash");
+    private abstract static class AbstractPathArgument implements PathArgument {
         private static final long serialVersionUID = -4546547994250849340L;
         private final QName nodeType;
-        private volatile transient Integer hash = null;
+        private transient int hashValue;
+        private transient volatile boolean hashGuard = false;
 
         protected AbstractPathArgument(final QName nodeType) {
-            this.nodeType = Preconditions.checkNotNull(nodeType);
+            this.nodeType = requireNonNull(nodeType);
         }
 
         @Override
@@ -382,7 +437,8 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         }
 
         @Override
-        public int compareTo(final PathArgument o) {
+        @SuppressWarnings("checkstyle:parameterName")
+        public int compareTo(@Nonnull final PathArgument o) {
             return nodeType.compareTo(o.getNodeType());
         }
 
@@ -392,13 +448,12 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
 
         @Override
         public final int hashCode() {
-            Integer ret = hash;
-            if (ret == null) {
-                ret = hashCodeImpl();
-                HASH_UPDATER.lazySet(this, ret);
+            if (!hashGuard) {
+                hashValue = hashCodeImpl();
+                hashGuard = true;
             }
 
-            return ret;
+            return hashValue;
         }
 
         @Override
@@ -421,7 +476,7 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         @Override
         public String toRelativeString(final PathArgument previous) {
             if (previous instanceof AbstractPathArgument) {
-                final QNameModule mod = ((AbstractPathArgument)previous).getNodeType().getModule();
+                final QNameModule mod = previous.getNodeType().getModule();
                 if (getNodeType().getModule().equals(mod)) {
                     return getNodeType().getLocalName();
                 }
@@ -431,63 +486,34 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         }
     }
 
-    /**
-     * Fluent Builder of Instance Identifier instances
-     */
-    public interface InstanceIdentifierBuilder extends Builder<YangInstanceIdentifier> {
-        /**
-         * Adds {@link NodeIdentifier} with supplied QName to path arguments of resulting instance identifier.
-         *
-         * @param nodeType QName of {@link NodeIdentifier} which will be added
-         * @return this builder
-         */
-        InstanceIdentifierBuilder node(QName nodeType);
-
-        /**
-         * Adds {@link NodeIdentifierWithPredicates} with supplied QName and key values to path arguments of resulting instance identifier.
-         *
-         * @param nodeType QName of {@link NodeIdentifierWithPredicates} which will be added
-         * @param keyValues Map of key components and their respective values for {@link NodeIdentifierWithPredicates}
-         * @return this builder
-         */
-        InstanceIdentifierBuilder nodeWithKey(QName nodeType, Map<QName, Object> keyValues);
-
-        /**
-         * Adds {@link NodeIdentifierWithPredicates} with supplied QName and key, value.
-         *
-         * @param nodeType QName of {@link NodeIdentifierWithPredicates} which will be added
-         * @param key QName of key which will be added
-         * @param value value of key which will be added
-         * @return this builder
-         */
-        InstanceIdentifierBuilder nodeWithKey(QName nodeType, QName key, Object value);
-
-        /**
-         *
-         * Builds an {@link YangInstanceIdentifier} with path arguments from this builder
-         *
-         * @return {@link YangInstanceIdentifier}
-         */
-        @Override
-        YangInstanceIdentifier build();
-
-        /*
-         * @deprecated use #build()
-         */
-        @Deprecated
-        YangInstanceIdentifier toInstance();
-    }
-
     /**
      * Simple path argument identifying a {@link org.opendaylight.yangtools.yang.data.api.schema.ContainerNode} or
      * {@link org.opendaylight.yangtools.yang.data.api.schema.LeafNode} leaf in particular subtree.
      */
     public static final class NodeIdentifier extends AbstractPathArgument {
         private static final long serialVersionUID = -2255888212390871347L;
+        private static final LoadingCache<QName, NodeIdentifier> CACHE = CacheBuilder.newBuilder().weakValues()
+                .build(new CacheLoader<QName, NodeIdentifier>() {
+                    @Override
+                    public NodeIdentifier load(@Nonnull final QName key) {
+                        return new NodeIdentifier(key);
+                    }
+                });
 
         public NodeIdentifier(final QName node) {
             super(node);
         }
+
+        /**
+         * Return a NodeIdentifier for a particular QName. Unlike the constructor, this factory method uses a global
+         * instance cache, resulting in object reuse for equal inputs.
+         *
+         * @param node Node's QName
+         * @return A {@link NodeIdentifier}
+         */
+        public static NodeIdentifier create(final QName node) {
+            return CACHE.getUnchecked(node);
+        }
     }
 
     /**
@@ -501,11 +527,13 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
 
         public NodeIdentifierWithPredicates(final QName node, final Map<QName, Object> keyValues) {
             super(node);
-            this.keyValues = ImmutableMap.copyOf(keyValues);
+            // Retains ImmutableMap for empty maps. For larger sizes uses a shared key set.
+            this.keyValues = ImmutableOffsetMap.unorderedCopyOf(keyValues);
         }
 
         public NodeIdentifierWithPredicates(final QName node, final QName key, final Object value) {
-            this(node, ImmutableMap.of(key, value));
+            super(node);
+            this.keyValues = SharedSingletonMap.unorderedOf(key, value);
         }
 
         public Map<QName, Object> getKeyValues() {
@@ -525,12 +553,18 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         }
 
         @Override
+        @SuppressWarnings("checkstyle:equalsHashCode")
         public boolean equals(final Object obj) {
             if (!super.equals(obj)) {
                 return false;
             }
 
             final Map<QName, Object> otherKeyValues = ((NodeIdentifierWithPredicates) obj).keyValues;
+
+            // TODO: benchmark to see if just calling equals() on the two maps is not faster
+            if (keyValues == otherKeyValues) {
+                return true;
+            }
             if (keyValues.size() != otherKeyValues.size()) {
                 return false;
             }
@@ -561,17 +595,17 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
      * Simple path argument identifying a {@link LeafSetEntryNode} leaf
      * overall data tree.
      */
-    public static final class NodeWithValue extends AbstractPathArgument {
+    public static final class NodeWithValue<T> extends AbstractPathArgument {
         private static final long serialVersionUID = -3637456085341738431L;
 
-        private final Object value;
+        private final T value;
 
-        public NodeWithValue(final QName node, final Object value) {
+        public NodeWithValue(final QName node, final T value) {
             super(node);
             this.value = value;
         }
 
-        public Object getValue() {
+        public T getValue() {
             return value;
         }
 
@@ -579,16 +613,17 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         protected int hashCodeImpl() {
             final int prime = 31;
             int result = super.hashCodeImpl();
-            result = prime * result + ((value == null) ? 0 : YangInstanceIdentifier.hashCode(value));
+            result = prime * result + YangInstanceIdentifier.hashCode(value);
             return result;
         }
 
         @Override
+        @SuppressWarnings("checkstyle:equalsHashCode")
         public boolean equals(final Object obj) {
             if (!super.equals(obj)) {
                 return false;
             }
-            final NodeWithValue other = (NodeWithValue) obj;
+            final NodeWithValue<?> other = (NodeWithValue<?>) obj;
             return Objects.deepEquals(value, other.value);
         }
 
@@ -604,9 +639,10 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
     }
 
     /**
-     * Composite path argument identifying a {@link org.opendaylight.yangtools.yang.data.api.schema.AugmentationNode} node in
-     * particular subtree.
+     * Composite path argument identifying a {@link org.opendaylight.yangtools.yang.data.api.schema.AugmentationNode}
+     * node in particular subtree.
      *
+     * <p>
      * Augmentation is uniquely identified by set of all possible child nodes.
      * This is possible
      * to identify instance of augmentation,
@@ -614,7 +650,6 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
      * statement must not add multiple nodes from same namespace
      * / module to the target node.
      *
-     *
      * @see <a href="http://tools.ietf.org/html/rfc6020#section-7.15">RFC6020</a>
      */
     public static final class AugmentationIdentifier implements PathArgument {
@@ -628,9 +663,8 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         }
 
         /**
-         *
          * Construct new augmentation identifier using supplied set of possible
-         * child nodes
+         * child nodes.
          *
          * @param childNames
          *            Set of possible child nodes.
@@ -640,7 +674,7 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         }
 
         /**
-         * Returns set of all possible child nodes
+         * Returns set of all possible child nodes.
          *
          * @return set of all possible child nodes.
          */
@@ -650,9 +684,7 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
 
         @Override
         public String toString() {
-            final StringBuilder sb = new StringBuilder("AugmentationIdentifier{");
-            sb.append("childNames=").append(childNames).append('}');
-            return sb.toString();
+            return "AugmentationIdentifier{" + "childNames=" + childNames + '}';
         }
 
         @Override
@@ -661,15 +693,15 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         }
 
         @Override
-        public boolean equals(final Object o) {
-            if (this == o) {
+        public boolean equals(final Object obj) {
+            if (this == obj) {
                 return true;
             }
-            if (!(o instanceof AugmentationIdentifier)) {
+            if (!(obj instanceof AugmentationIdentifier)) {
                 return false;
             }
 
-            AugmentationIdentifier that = (AugmentationIdentifier) o;
+            AugmentationIdentifier that = (AugmentationIdentifier) obj;
             return childNames.equals(that.childNames);
         }
 
@@ -679,7 +711,8 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         }
 
         @Override
-        public int compareTo(final PathArgument o) {
+        @SuppressWarnings("checkstyle:parameterName")
+        public int compareTo(@Nonnull final PathArgument o) {
             if (!(o instanceof AugmentationIdentifier)) {
                 return -1;
             }
@@ -688,14 +721,19 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
             int thisSize = childNames.size();
             int otherSize = otherChildNames.size();
             if (thisSize == otherSize) {
-                Iterator<QName> otherIterator = otherChildNames.iterator();
-                for (QName name : childNames) {
-                    int c = name.compareTo(otherIterator.next());
-                    if (c != 0) {
-                        return c;
-                    }
+                // Quick Set-based comparison
+                if (childNames.equals(otherChildNames)) {
+                    return 0;
                 }
-                return 0;
+
+                // We already know the sets are not equal, but have equal size, hence the sets differ in their elements,
+                // but potentially share a common set of elements. The most consistent way of comparing them is using
+                // total ordering defined by QName's compareTo. Hence convert both sets to lists ordered
+                // by QName.compareTo() and decide on the first differing element.
+                final List<QName> diff = new ArrayList<>(Sets.symmetricDifference(childNames, otherChildNames));
+                verify(!diff.isEmpty(), "Augmentation identifiers %s and %s report no difference", this, o);
+                diff.sort(QName::compareTo);
+                return childNames.contains(diff.get(0)) ? -1 : 1;
             } else if (thisSize < otherSize) {
                 return 1;
             } else {
@@ -704,128 +742,74 @@ public final class YangInstanceIdentifier implements Path<YangInstanceIdentifier
         }
     }
 
-    private static class BuilderImpl implements InstanceIdentifierBuilder {
-        private final HashCodeBuilder<PathArgument> hash;
-        private final List<PathArgument> path;
-
-        public BuilderImpl() {
-            this.hash = new HashCodeBuilder<>();
-            this.path = new ArrayList<>();
-        }
-
-        public BuilderImpl(final Iterable<PathArgument> prefix, final int hash) {
-            this.path = Lists.newArrayList(prefix);
-            this.hash = new HashCodeBuilder<>(hash);
-        }
-
-        @Override
-        public InstanceIdentifierBuilder node(final QName nodeType) {
-            final PathArgument arg = new NodeIdentifier(nodeType);
-            path.add(arg);
-            hash.addArgument(arg);
-            return this;
-        }
-
-        @Override
-        public InstanceIdentifierBuilder nodeWithKey(final QName nodeType, final QName key, final Object value) {
-            final PathArgument arg = new NodeIdentifierWithPredicates(nodeType, key, value);
-            path.add(arg);
-            hash.addArgument(arg);
-            return this;
-        }
-
-        @Override
-        public InstanceIdentifierBuilder nodeWithKey(final QName nodeType, final Map<QName, Object> keyValues) {
-            final PathArgument arg = new NodeIdentifierWithPredicates(nodeType, keyValues);
-            path.add(arg);
-            hash.addArgument(arg);
-            return this;
-        }
-
-        @Override
-        @Deprecated
-        public YangInstanceIdentifier toInstance() {
-            return build();
-        }
-
-        @Override
-        public YangInstanceIdentifier build() {
-            return new YangInstanceIdentifier(ImmutableList.copyOf(path), hash.build());
-        }
-    }
-
-    @Override
-    public boolean contains(final YangInstanceIdentifier other) {
-        Preconditions.checkArgument(other != null, "other should not be null");
-
-        final Iterator<?> lit = pathArguments.iterator();
-        final Iterator<?> oit = other.pathArguments.iterator();
-
-        while (lit.hasNext()) {
-            if (!oit.hasNext()) {
-                return false;
-            }
-
-            if (!lit.next().equals(oit.next())) {
-                return false;
-            }
-        }
+    /**
+     * Fluent Builder of Instance Identifier instances.
+     */
+    public interface InstanceIdentifierBuilder extends Builder<YangInstanceIdentifier> {
+        /**
+         * Adds a {@link PathArgument} to path arguments of resulting instance identifier.
+         *
+         * @param arg A {@link PathArgument} to be added
+         * @return this builder
+         */
+        InstanceIdentifierBuilder node(PathArgument arg);
 
-        return true;
-    }
+        /**
+         * Adds {@link NodeIdentifier} with supplied QName to path arguments of resulting instance identifier.
+         *
+         * @param nodeType QName of {@link NodeIdentifier} which will be added
+         * @return this builder
+         */
+        InstanceIdentifierBuilder node(QName nodeType);
 
-    @Override
-    public String toString() {
-        /*
-         * The toStringCache is safe, since the object contract requires
-         * immutability of the object and all objects referenced from this
-         * object.
-         * Used lists, maps are immutable. Path Arguments (elements) are also
-         * immutable, since the PathArgument contract requires immutability.
-         * The cache is thread-safe - if multiple computations occurs at the
-         * same time, cache will be overwritten with same result.
+        /**
+         * Adds {@link NodeIdentifierWithPredicates} with supplied QName and key values to path arguments of resulting
+         * instance identifier.
+         *
+         * @param nodeType QName of {@link NodeIdentifierWithPredicates} which will be added
+         * @param keyValues Map of key components and their respective values for {@link NodeIdentifierWithPredicates}
+         * @return this builder
          */
-        String ret = toStringCache;
-        if (ret == null) {
-            final StringBuilder builder = new StringBuilder("/");
-            PathArgument prev = null;
-            for (PathArgument argument : getPathArguments()) {
-                if (prev != null) {
-                    builder.append('/');
-                }
-                builder.append(argument.toRelativeString(prev));
-                prev = argument;
-            }
+        InstanceIdentifierBuilder nodeWithKey(QName nodeType, Map<QName, Object> keyValues);
 
-            ret = builder.toString();
-            TOSTRINGCACHE_UPDATER.lazySet(this, ret);
-        }
-        return ret;
-    }
+        /**
+         * Adds {@link NodeIdentifierWithPredicates} with supplied QName and key, value.
+         *
+         * @param nodeType QName of {@link NodeIdentifierWithPredicates} which will be added
+         * @param key QName of key which will be added
+         * @param value value of key which will be added
+         * @return this builder
+         */
+        InstanceIdentifierBuilder nodeWithKey(QName nodeType, QName key, Object value);
 
-    private void readObject(final ObjectInputStream inputStream) throws IOException, ClassNotFoundException {
-        inputStream.defaultReadObject();
+        /**
+         * Adds a collection of {@link PathArgument}s to path arguments of resulting instance identifier.
+         *
+         * @param args {@link PathArgument}s to be added
+         * @return this builder
+         * @throws NullPointerException if any of the arguments is null
+         */
+        @Beta
+        InstanceIdentifierBuilder append(Collection<? extends PathArgument> args);
 
-        try {
-            PATHARGUMENTS_FIELD.set(this, legacyPath);
-        } catch (IllegalArgumentException | IllegalAccessException e) {
-            throw new IOException(e);
+        /**
+         * Adds a collection of {@link PathArgument}s to path arguments of resulting instance identifier.
+         *
+         * @param args {@link PathArgument}s to be added
+         * @return this builder
+         * @throws NullPointerException if any of the arguments is null
+         */
+        @Beta
+        default InstanceIdentifierBuilder append(final PathArgument... args) {
+            return append(Arrays.asList(args));
         }
-    }
-
-    private Object readResolve() throws ObjectStreamException {
-        return legacyPath.isEmpty() ? EMPTY : this;
-    }
 
-    private void writeObject(final ObjectOutputStream outputStream) throws IOException {
-        /*
-         * This may look strange, but what we are doing here is side-stepping the fact
-         * that pathArguments is not generally serializable. We are forcing instantiation
-         * of the legacy path, which is an ImmutableList (thus Serializable) and write
-         * it out. The read path does the opposite -- it reads the legacyPath and then
-         * uses invocation API to set the field.
+        /**
+         * Builds an {@link YangInstanceIdentifier} with path arguments from this builder.
+         *
+         * @return {@link YangInstanceIdentifier}
          */
-        getLegacyPath();
-        outputStream.defaultWriteObject();
+        @Override
+        YangInstanceIdentifier build();
     }
 }