API Change: Implemented various getAs methods to return null.

gson/src/main/java/com/google/gson/JsonNull.java

@@ -17,6 +17,8 @@
 package com.google.gson;
 
 import java.io.IOException;
+import java.math.BigDecimal;
+import java.math.BigInteger;
 
 /**
  * A class representing a Json {@code null} value.
@@ -35,13 +37,49 @@ public final class JsonNull extends JsonElement {
 
   /**
    * Creates a new JsonNull object.
-   * Deprecated. Use {@link #INSTANCE} instead
+   * Deprecated since Gson version 1.8. Use {@link #INSTANCE} instead
    */
   @Deprecated
   public JsonNull() {
     // Do nothing
   }
-  
+
+  /**
+   * Returns null
+   * @since 1.8
+   */
+  @Override
+  public Number getAsNumber() {
+    return null;
+  }
+
+  /**
+   * Returns null
+   * @Since 1.8
+   */
+  @Override
+  public String getAsString() {
+    return null;
+  }
+
+  /**
+   * Returns null
+   * @Since 1.8
+   */
+  @Override
+  public BigDecimal getAsBigDecimal() {
+    return null;
+  }
+
+  /**
+   * Returns null
+   * @Since 1.8
+   */
+  @Override
+  public BigInteger getAsBigInteger() {
+    return null;
+  }
+
   @Override
   protected void toString(Appendable sb, Escaper escaper) throws IOException {
     sb.append("null");