removed the methods that return null for various getAs methods per discussions with Jesse and Joel.

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

@@ -17,8 +17,6 @@
 package com.google.gson;
 
 import java.io.IOException;
-import java.math.BigDecimal;
-import java.math.BigInteger;
 
 /**
  * A class representing a Json {@code null} value.
@@ -44,42 +42,6 @@ public final class JsonNull extends JsonElement {
     // 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");