Fix #2204

release-notes/VERSION-2.x

@@ -16,6 +16,7 @@ Project: jackson-databind
 #2126: `DeserializationContext.instantiationException()` throws `InvalidDefinitionException`
 #2153: Add `JsonMapper` to replace generic `ObjectMapper` usage
 #2187: Make `JsonNode.toString()` use shared `ObjectMapper` to produce valid json
+#2204: Add `JsonNode.isEmpty()` as convenience alias
 
 2.9.8 (not yet released)
 

src/main/java/com/fasterxml/jackson/databind/JsonNode.java

@@ -81,6 +81,17 @@ protected JsonNode() { }
     @Override
     public int size() { return 0; }
 
+    /**
+     * Convenience method that is functionally same as:
+     *<pre>
+     *    size() == 0
+     *<pre>
+     * for all node types.
+     *
+     * @since 2.10
+     */
+    public boolean isEmpty() { return size() == 0; }
+
     @Override
     public final boolean isValueNode()
     {

src/main/java/com/fasterxml/jackson/databind/node/ArrayNode.java

@@ -99,14 +99,17 @@ public int size() {
         return _children.size();
     }
 
+    @Override // since 2.10
+    public boolean isEmpty() { return _children.isEmpty(); }
+
     @Override
     public Iterator<JsonNode> elements() {
         return _children.iterator();
     }
 
     @Override
     public JsonNode get(int index) {
-        if (index >= 0 && index < _children.size()) {
+        if ((index >= 0) && (index < _children.size())) {
             return _children.get(index);
         }
         return null;

src/main/java/com/fasterxml/jackson/databind/node/BaseJsonNode.java

@@ -105,12 +105,12 @@ public abstract void serializeWithType(JsonGenerator jgen, SerializerProvider pr
     */
 
    @Override
-   public final String toString() {
+   public String toString() {
        return InternalNodeMapper.nodeToString(this);
    }
 
    @Override
-   public final String toPrettyString() {
+   public String toPrettyString() {
        return InternalNodeMapper.nodeToPrettyString(this);
    }
 }

src/main/java/com/fasterxml/jackson/databind/node/ObjectNode.java

@@ -90,6 +90,9 @@ public int size() {
         return _children.size();
     }
 
+    @Override // since 2.10
+    public boolean isEmpty() { return _children.isEmpty(); }
+
     @Override
     public Iterator<JsonNode> elements() {
         return _children.values().iterator();

src/main/java/com/fasterxml/jackson/databind/node/ValueNode.java

@@ -48,9 +48,18 @@ public void serializeWithType(JsonGenerator g, SerializerProvider provider,
     }
 
     /*
-     **********************************************************************
-     * Navigation methods
-     **********************************************************************
+    /**********************************************************************
+    /* Basic property access
+    /**********************************************************************
+     */
+
+    @Override
+    public boolean isEmpty() { return true; }
+
+    /*
+    /**********************************************************************
+    /* Navigation methods
+    /**********************************************************************
      */
 
     @Override

src/test/java/com/fasterxml/jackson/databind/node/ArrayNodeTest.java

@@ -25,9 +25,11 @@ public void testDirectCreation() throws IOException
         assertStandardEquals(n);
         assertFalse(n.elements().hasNext());
         assertFalse(n.fieldNames().hasNext());
+        assertTrue(n.isEmpty());
         TextNode text = TextNode.valueOf("x");
         n.add(text);
         assertEquals(1, n.size());
+        assertFalse(n.isEmpty());
         assertFalse(0 == n.hashCode());
         assertTrue(n.elements().hasNext());
         // no field names for arrays
@@ -149,6 +151,7 @@ public void testAdds()
         n.add(new BigDecimal("0.2"));
         n.add(BigInteger.TEN);
         assertEquals(9, n.size());
+        assertFalse(n.isEmpty());
 
         assertNotNull(n.insertArray(0));
         assertNotNull(n.insertObject(0));

src/test/java/com/fasterxml/jackson/databind/node/NodeTestBase.java

@@ -25,6 +25,7 @@ protected void assertNodeNumbers(JsonNode n, int expInt, double expDouble)
         assertEquals((long) expInt, n.asLong(19L));
         assertEquals(expDouble, n.asDouble());
         assertEquals(expDouble, n.asDouble(-19.25));
-    }
 
+        assertTrue(n.isEmpty());
+    }
 }

src/test/java/com/fasterxml/jackson/databind/node/ObjectNodeTest.java

@@ -81,6 +81,7 @@ public void testSimpleObject() throws Exception
         assertFalse(root.isArray());
         assertTrue(root.isObject());
         assertEquals(2, root.size());
+        assertFalse(root.isEmpty());
 
         Iterator<JsonNode> it = root.iterator();
         assertNotNull(it);
@@ -127,7 +128,8 @@ public void testBasics()
     {
         ObjectNode n = new ObjectNode(JsonNodeFactory.instance);
         assertStandardEquals(n);
-
+        assertTrue(n.isEmpty());
+
         assertFalse(n.elements().hasNext());
         assertFalse(n.fields().hasNext());
         assertFalse(n.fieldNames().hasNext());

src/test/java/com/fasterxml/jackson/databind/node/TestNullNode.java

@@ -40,6 +40,7 @@ public void testBasicsWithNullNode() throws Exception
         assertEquals(BigInteger.ZERO, n.bigIntegerValue());
 
         assertEquals(0, n.size());
+        assertTrue(n.isEmpty());
         assertFalse(n.elements().hasNext());
         assertFalse(n.fieldNames().hasNext());
         // path is never null; but does point to missing node

src/test/java/com/fasterxml/jackson/databind/node/TextNodeTest.java

@@ -9,6 +9,9 @@ public void testText()
         assertStandardEquals(empty);
         assertSame(TextNode.EMPTY_STRING_NODE, empty);
 
+        assertEquals(0, empty.size());
+        assertTrue(empty.isEmpty());
+
         assertNodeNumbers(TextNode.valueOf("-3"), -3, -3.0);
         assertNodeNumbers(TextNode.valueOf("17.75"), 17, 17.75);