fixes #56: EMPTY_JSON_OBJECT and EMPTY_JSON_ARRAY should be immutable

api/src/main/java/javax/json/EmptyArray.java

@@ -0,0 +1,136 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ * Copyright (c) 2017 Oracle and/or its affiliates. All rights reserved.
+ *
+ * The contents of this file are subject to the terms of either the GNU
+ * General Public License Version 2 only ("GPL") or the Common Development
+ * and Distribution License("CDDL") (collectively, the "License").  You
+ * may not use this file except in compliance with the License.  You can
+ * obtain a copy of the License at
+ * https://oss.oracle.com/licenses/CDDL+GPL-1.1
+ * or LICENSE.txt.  See the License for the specific
+ * language governing permissions and limitations under the License.
+ *
+ * When distributing the software, include this License Header Notice in each
+ * file and include the License file at LICENSE.txt.
+ *
+ * GPL Classpath Exception:
+ * Oracle designates this particular file as subject to the "Classpath"
+ * exception as provided by Oracle in the GPL Version 2 section of the License
+ * file that accompanied this code.
+ *
+ * Modifications:
+ * If applicable, add the following below the License Header, with the fields
+ * enclosed by brackets [] replaced by your own identifying information:
+ * "Portions Copyright [year] [name of copyright owner]"
+ *
+ * Contributor(s):
+ * If you wish your version of this file to be governed by only the CDDL or
+ * only the GPL Version 2, indicate your decision by adding "[Contributor]
+ * elects to include this software in this distribution under the [CDDL or GPL
+ * Version 2] license."  If you don't indicate a single choice of license, a
+ * recipient has the option to distribute your version of this file under
+ * either the CDDL, the GPL Version 2 or to extend the choice of license to
+ * its licensees as provided above.  However, if you add GPL Version 2 code
+ * and therefore, elected the GPL Version 2 license, then the option applies
+ * only if the new code is made subject to such option by the copyright
+ * holder.
+ */
+package javax.json;
+
+import java.io.Serializable;
+import java.util.AbstractList;
+import java.util.Collections;
+import java.util.List;
+import java.util.RandomAccess;
+
+/**
+ * Private implementation of immutable {@link JsonArray}.
+ *
+ * @author Lukas Jungmann
+ */
+final class EmptyArray extends AbstractList<JsonValue> implements JsonArray, Serializable, RandomAccess {
+
+    private static final long serialVersionUID = 7295439472061642859L;
+
+    @Override
+    public JsonValue get(int index) {
+        throw new IndexOutOfBoundsException("Index: " + index);
+    }
+
+    @Override
+    public int size() {
+        return 0;
+    }
+
+    @Override
+    public JsonObject getJsonObject(int index) {
+        return (JsonObject) get(index);
+    }
+
+    @Override
+    public JsonArray getJsonArray(int index) {
+        return (JsonArray) get(index);
+    }
+
+    @Override
+    public JsonNumber getJsonNumber(int index) {
+        return (JsonNumber) get(index);
+    }
+
+    @Override
+    public JsonString getJsonString(int index) {
+        return (JsonString) get(index);
+    }
+
+    @Override
+    public <T extends JsonValue> List<T> getValuesAs(Class<T> clazz) {
+        return Collections.emptyList();
+    }
+
+    @Override
+    public String getString(int index) {
+        return getJsonString(index).getString();
+    }
+
+    @Override
+    public String getString(int index, String defaultValue) {
+        return defaultValue;
+    }
+
+    @Override
+    public int getInt(int index) {
+        return getJsonNumber(index).intValue();
+    }
+
+    @Override
+    public int getInt(int index, int defaultValue) {
+        return defaultValue;
+    }
+
+    @Override
+    public boolean getBoolean(int index) {
+        return get(index) == JsonValue.TRUE;
+    }
+
+    @Override
+    public boolean getBoolean(int index, boolean defaultValue) {
+        return defaultValue;
+    }
+
+    @Override
+    public boolean isNull(int index) {
+        return get(index) == JsonValue.NULL;
+    }
+
+    @Override
+    public ValueType getValueType() {
+        return ValueType.ARRAY;
+    }
+
+    // Preserves singleton property
+    private Object readResolve() {
+        return JsonValue.EMPTY_JSON_ARRAY;
+    }
+}

api/src/main/java/javax/json/EmptyObject.java

@@ -0,0 +1,126 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ * Copyright (c) 2017 Oracle and/or its affiliates. All rights reserved.
+ *
+ * The contents of this file are subject to the terms of either the GNU
+ * General Public License Version 2 only ("GPL") or the Common Development
+ * and Distribution License("CDDL") (collectively, the "License").  You
+ * may not use this file except in compliance with the License.  You can
+ * obtain a copy of the License at
+ * https://oss.oracle.com/licenses/CDDL+GPL-1.1
+ * or LICENSE.txt.  See the License for the specific
+ * language governing permissions and limitations under the License.
+ *
+ * When distributing the software, include this License Header Notice in each
+ * file and include the License file at LICENSE.txt.
+ *
+ * GPL Classpath Exception:
+ * Oracle designates this particular file as subject to the "Classpath"
+ * exception as provided by Oracle in the GPL Version 2 section of the License
+ * file that accompanied this code.
+ *
+ * Modifications:
+ * If applicable, add the following below the License Header, with the fields
+ * enclosed by brackets [] replaced by your own identifying information:
+ * "Portions Copyright [year] [name of copyright owner]"
+ *
+ * Contributor(s):
+ * If you wish your version of this file to be governed by only the CDDL or
+ * only the GPL Version 2, indicate your decision by adding "[Contributor]
+ * elects to include this software in this distribution under the [CDDL or GPL
+ * Version 2] license."  If you don't indicate a single choice of license, a
+ * recipient has the option to distribute your version of this file under
+ * either the CDDL, the GPL Version 2 or to extend the choice of license to
+ * its licensees as provided above.  However, if you add GPL Version 2 code
+ * and therefore, elected the GPL Version 2 license, then the option applies
+ * only if the new code is made subject to such option by the copyright
+ * holder.
+ */
+
+package javax.json;
+
+import java.io.Serializable;
+import java.util.AbstractMap;
+import java.util.Collections;
+import java.util.Set;
+
+/**
+ * Private implementation of immutable {@link JsonObject}.
+ *
+ * @author Lukas Jungmann
+ */
+final class EmptyObject extends AbstractMap<String, JsonValue> implements JsonObject, Serializable {
+
+    private static final long serialVersionUID = -1461653546889072583L;
+
+    @Override
+    public Set<Entry<String, JsonValue>> entrySet() {
+        return Collections.<Entry<String, JsonValue>>emptySet();
+    }
+
+    @Override
+    public JsonArray getJsonArray(String name) {
+        return (JsonArray) get(name);
+    }
+
+    @Override
+    public JsonObject getJsonObject(String name) {
+        return (JsonObject) get(name);
+    }
+
+    @Override
+    public JsonNumber getJsonNumber(String name) {
+        return (JsonNumber) get(name);
+    }
+
+    @Override
+    public JsonString getJsonString(String name) {
+        return (JsonString) get(name);
+    }
+
+    @Override
+    public String getString(String name) {
+        return getJsonString(name).getString();
+    }
+
+    @Override
+    public String getString(String name, String defaultValue) {
+        return defaultValue;
+    }
+
+    @Override
+    public int getInt(String name) {
+        return getJsonNumber(name).intValue();
+    }
+
+    @Override
+    public int getInt(String name, int defaultValue) {
+        return defaultValue;
+    }
+
+    @Override
+    public boolean getBoolean(String name) {
+        throw new NullPointerException();
+    }
+
+    @Override
+    public boolean getBoolean(String name, boolean defaultValue) {
+        return defaultValue;
+    }
+
+    @Override
+    public boolean isNull(String name) {
+        throw new NullPointerException();
+    }
+
+    @Override
+    public ValueType getValueType() {
+        return ValueType.OBJECT;
+    }
+
+    // Preserves singleton property
+    private Object readResolve() {
+        return JsonValue.EMPTY_JSON_OBJECT;
+    }
+}

api/src/main/java/javax/json/JsonArray.java

@@ -291,7 +291,7 @@ default <T, K extends JsonValue> List<T> getValuesAs(Function<K, T> func) {
      *
      * @param index index of the JSON null value
      * @return return true if the value at the specified location is
-     * {@code JsonValue.NUL}, otherwise false
+     * {@code JsonValue.NULL}, otherwise false
      * @throws IndexOutOfBoundsException if the index is out of range
      */
     boolean isNull(int index);

api/src/main/java/javax/json/JsonValue.java

@@ -43,29 +43,29 @@
 /**
  * <code>JsonValue</code> represents an immutable JSON value.
  *
- * 
+ *
  * <p>A JSON value is one of the following:
  * an object ({@link JsonObject}), an array ({@link JsonArray}),
  * a number ({@link JsonNumber}), a string ({@link JsonString}),
- * {@code true} ({@link JsonValue#TRUE JsonValue.TRUE}), {@code false} 
+ * {@code true} ({@link JsonValue#TRUE JsonValue.TRUE}), {@code false}
  * ({@link JsonValue#FALSE JsonValue.FALSE}),
  * or {@code null} ({@link JsonValue#NULL JsonValue.NULL}).
  */
 public interface JsonValue {
 
     /**
      * The empty JSON object.
-     * 
+     *
      * @since 1.1
      */
-    static final JsonObject EMPTY_JSON_OBJECT = Json.createObjectBuilder().build();
+    static final JsonObject EMPTY_JSON_OBJECT = new EmptyObject();
 
     /**
      * The empty JSON array.
-     * 
+     *
      * @since 1.1
      */
-    static final JsonArray EMPTY_JSON_ARRAY = Json.createArrayBuilder().build();
+    static final JsonArray EMPTY_JSON_ARRAY = new EmptyArray();
 
     /**
      * Indicates the type of a {@link JsonValue} object.