Port SimpleImmutableEntry for Android2.2 or below

src/main/java/org/msgpack/type/SequentialMapValueImpl.java

@@ -27,6 +27,7 @@
 import java.util.NoSuchElementException;
 import java.io.IOException;
 import org.msgpack.packer.Packer;
+import org.msgpack.util.PortedImmutableEntry;
 
 class SequentialMapValueImpl extends AbstractMapValue {
     private static SequentialMapValueImpl emptyInstance = new SequentialMapValueImpl(new Value[0], true);
@@ -89,6 +90,17 @@ private static class EntrySetIterator implements
             Iterator<Map.Entry<Value, Value>> {
         private Value[] array;
         private int pos;
+        private static final boolean hasDefaultImmutableEntry;
+        static {
+            boolean hasIt = true;
+            try {
+                Class.forName("java.util.AbstractMap.SimpleImmutableEntry");
+            } catch (ClassNotFoundException e) {
+                hasIt = false;
+            } finally {
+                hasDefaultImmutableEntry = hasIt;
+            }
+        }
 
         EntrySetIterator(Value[] array) {
             this.array = array;
@@ -105,8 +117,13 @@ public Map.Entry<Value, Value> next() {
             if (pos >= array.length) {
                 throw new NoSuchElementException(); // TODO message
             }
-            Map.Entry<Value, Value> pair =
-                new AbstractMap.SimpleImmutableEntry<Value, Value>(array[pos], array[pos + 1]);
+
+            Value key = array[pos];
+            Value value = array[pos + 1];
+            Map.Entry<Value, Value> pair = hasDefaultImmutableEntry ?
+                new AbstractMap.SimpleImmutableEntry<Value, Value>(key, value) :
+                new PortedImmutableEntry<Value, Value>(key, value);
+
             pos += 2;
             return pair;
         }

src/main/java/org/msgpack/util/PortedImmutableEntry.java

@@ -0,0 +1,87 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one or more
+ *  contributor license agreements.  See the NOTICE file distributed with
+ *  this work for additional information regarding copyright ownership.
+ *  The ASF licenses this file to You under the Apache License, Version 2.0
+ *  (the "License"); you may not use this file except in compliance with
+ *  the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+package org.msgpack.util;
+
+import java.io.Serializable;
+import java.util.Map;
+
+/**
+ * An immutable key-value mapping. Despite the name, this class is non-final
+ * and its subclasses may be mutable.
+ * 
+ * This class is ported from java.util.AbstractMap$SimpleImmutableEntry of
+ * https://github.com/OESF/OHA-Android-4.0.3_r1.0 (Apache License).
+ */
+public class PortedImmutableEntry<K, V> implements Map.Entry<K, V>, Serializable {
+    private static final long serialVersionUID = -4564047655287765373L;
+
+    private final K key;
+    private final V value;
+
+    public PortedImmutableEntry(K theKey, V theValue) {
+        key = theKey;
+        value = theValue;
+    }
+
+    /**
+     * Constructs an instance with the key and value of {@code copyFrom}.
+     */
+    public PortedImmutableEntry(Map.Entry<? extends K, ? extends V> copyFrom) {
+        key = copyFrom.getKey();
+        value = copyFrom.getValue();
+    }
+
+    public K getKey() {
+        return key;
+    }
+
+    public V getValue() {
+        return value;
+    }
+
+    /**
+     * This base implementation throws {@code UnsupportedOperationException}
+     * always.
+     */
+    public V setValue(V object) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override public boolean equals(Object object) {
+        if (this == object) {
+            return true;
+        }
+        if (object instanceof Map.Entry) {
+            Map.Entry<?, ?> entry = (Map.Entry<?, ?>) object;
+            return (key == null ? entry.getKey() == null : key.equals(entry
+                    .getKey()))
+                    && (value == null ? entry.getValue() == null : value
+                            .equals(entry.getValue()));
+        }
+        return false;
+    }
+
+    @Override public int hashCode() {
+        return (key == null ? 0 : key.hashCode())
+                ^ (value == null ? 0 : value.hashCode());
+    }
+
+    @Override public String toString() {
+        return key + "=" + value;
+    }
+}