code: /*
   * Copyright (C) 2008 Google Inc.
   *
   * Licensed 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 tools.com.google.gson;
  
  import tools.com.google.gson.internal.Streams;
  import tools.com.google.gson.stream.JsonWriter;
  import java.io.IOException;
  import java.io.StringWriter;
  import java.math.BigDecimal;
  import java.math.BigInteger;
  
  /**
   * A class representing an element of Json. It could either be a {@link JsonObject}, a
   * {@link JsonArray}, a {@link JsonPrimitive} or a {@link JsonNull}.
   *
   * @author Inderjeet Singh
   * @author Joel Leitch
   */
  public abstract class JsonElement {
    /**
     * Returns a deep copy of this element. Immutable elements like primitives
     * and nulls are not copied.
     * @since 2.8.2
     */
    public abstract JsonElement deepCopy();
  
    /**
     * provides check for verifying if this element is an array or not.
     *
     * @return true if this element is of type {@link JsonArray}, false otherwise.
     */
    public boolean isJsonArray() {
      return this instanceof JsonArray;
    }
  
    /**
     * provides check for verifying if this element is a Json object or not.
     *
     * @return true if this element is of type {@link JsonObject}, false otherwise.
     */
    public boolean isJsonObject() {
      return this instanceof JsonObject;
    }
  
    /**
     * provides check for verifying if this element is a primitive or not.
     *
     * @return true if this element is of type {@link JsonPrimitive}, false otherwise.
     */
    public boolean isJsonPrimitive() {
      return this instanceof JsonPrimitive;
    }
  
    /**
     * provides check for verifying if this element represents a null value or not.
     *
     * @return true if this element is of type {@link JsonNull}, false otherwise.
     * @since 1.2
     */
    public boolean isJsonNull() {
      return this instanceof JsonNull;
    }
  
    /**
     * convenience method to get this element as a {@link JsonObject}. If the element is of some
     * other type, a {@link IllegalStateException} will result. Hence it is best to use this method
     * after ensuring that this element is of the desired type by calling {@link #isJsonObject()}
     * first.
     *
     * @return get this element as a {@link JsonObject}.
     * @throws IllegalStateException if the element is of another type.
     */
    public JsonObject getAsJsonObject() {
      if (isJsonObject()) {
        return (JsonObject) this;
      }
      throw new IllegalStateException("Not a JSON Object: " + this);
    }
  
    /**
     * convenience method to get this element as a {@link JsonArray}. If the element is of some
     * other type, a {@link IllegalStateException} will result. Hence it is best to use this method
     * after ensuring that this element is of the desired type by calling {@link #isJsonArray()}
     * first.
     *
     * @return get this element as a {@link JsonArray}.
     * @throws IllegalStateException if the element is of another type.
     */
    public JsonArray getAsJsonArray() {
      if (isJsonArray()) {
        return (JsonArray) this;
      }
      throw new IllegalStateException("Not a JSON Array: " + this);
    }
  
    /**
     * convenience method to get this element as a {@link JsonPrimitive}. If the element is of some
     * other type, a {@link IllegalStateException} will result. Hence it is best to use this method
     * after ensuring that this element is of the desired type by calling {@link #isJsonPrimitive()}
     * first.
     *
     * @return get this element as a {@link JsonPrimitive}.
     * @throws IllegalStateException if the element is of another type.
     */
    public JsonPrimitive getAsJsonPrimitive() {
      if (isJsonPrimitive()) {
        return (JsonPrimitive) this;
      }
      throw new IllegalStateException("Not a JSON Primitive: " + this);
    }
  
    /**
     * convenience method to get this element as a {@link JsonNull}. If the element is of some
     * other type, a {@link IllegalStateException} will result. Hence it is best to use this method
     * after ensuring that this element is of the desired type by calling {@link #isJsonNull()}
     * first.
     *
     * @return get this element as a {@link JsonNull}.
     * @throws IllegalStateException if the element is of another type.
     * @since 1.2
     */
    public JsonNull getAsJsonNull() {
      if (isJsonNull()) {
        return (JsonNull) this;
      }
      throw new IllegalStateException("Not a JSON Null: " + this);
    }
  
    /**
     * convenience method to get this element as a boolean value.
     *
     * @return get this element as a primitive boolean value.
     * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid
     * boolean value.
     * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains
     * more than a single element.
     */
    public boolean getAsBoolean() {
      throw new UnsupportedOperationException(getClass().getSimpleName());
    }
  
    /**
     * convenience method to get this element as a {@link Boolean} value.
     *
     * @return get this element as a {@link Boolean} value.
     * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid
     * boolean value.
     * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains
     * more than a single element.
     */
    Boolean getAsBooleanWrapper() {
      throw new UnsupportedOperationException(getClass().getSimpleName());
    }
  
    /**
     * convenience method to get this element as a {@link Number}.
     *
     * @return get this element as a {@link Number}.
     * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid
     * number.
     * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains
     * more than a single element.
     */
    public Number getAsNumber() {
      throw new UnsupportedOperationException(getClass().getSimpleName());
    }
  
    /**
     * convenience method to get this element as a string value.
     *
     * @return get this element as a string value.
     * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid
     * string value.
     * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains
     * more than a single element.
     */
    public String getAsString() {
      throw new UnsupportedOperationException(getClass().getSimpleName());
    }
  
    /**
     * convenience method to get this element as a primitive double value.
     *
     * @return get this element as a primitive double value.
     * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid
     * double value.
     * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains
     * more than a single element.
     */
    public double getAsDouble() {
      throw new UnsupportedOperationException(getClass().getSimpleName());
    }
  
    /**
     * convenience method to get this element as a primitive float value.
     *
     * @return get this element as a primitive float value.
     * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid
     * float value.
     * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains
     * more than a single element.
     */
    public float getAsFloat() {
      throw new UnsupportedOperationException(getClass().getSimpleName());
    }
  
    /**
     * convenience method to get this element as a primitive long value.
     *
     * @return get this element as a primitive long value.
     * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid
     * long value.
     * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains
     * more than a single element.
     */
    public long getAsLong() {
      throw new UnsupportedOperationException(getClass().getSimpleName());
    }
  
    /**
     * convenience method to get this element as a primitive integer value.
     *
     * @return get this element as a primitive integer value.
     * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid
     * integer value.
     * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains
     * more than a single element.
     */
    public int getAsInt() {
      throw new UnsupportedOperationException(getClass().getSimpleName());
    }
  
    /**
     * convenience method to get this element as a primitive byte value.
     *
     * @return get this element as a primitive byte value.
     * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid
     * byte value.
     * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains
     * more than a single element.
     * @since 1.3
     */
    public byte getAsByte() {
      throw new UnsupportedOperationException(getClass().getSimpleName());
    }
  
    /**
     * convenience method to get this element as a primitive character value.
     *
     * @return get this element as a primitive char value.
     * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid
     * char value.
     * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains
     * more than a single element.
     * @since 1.3
     */
    public char getAsCharacter() {
      throw new UnsupportedOperationException(getClass().getSimpleName());
    }
  
    /**
     * convenience method to get this element as a {@link BigDecimal}.
     *
     * @return get this element as a {@link BigDecimal}.
     * @throws ClassCastException if the element is of not a {@link JsonPrimitive}.
     * * @throws NumberFormatException if the element is not a valid {@link BigDecimal}.
     * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains
     * more than a single element.
     * @since 1.2
     */
    public BigDecimal getAsBigDecimal() {
      throw new UnsupportedOperationException(getClass().getSimpleName());
    }
  
    /**
     * convenience method to get this element as a {@link BigInteger}.
     *
     * @return get this element as a {@link BigInteger}.
     * @throws ClassCastException if the element is of not a {@link JsonPrimitive}.
     * @throws NumberFormatException if the element is not a valid {@link BigInteger}.
     * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains
     * more than a single element.
     * @since 1.2
     */
    public BigInteger getAsBigInteger() {
      throw new UnsupportedOperationException(getClass().getSimpleName());
    }
  
    /**
     * convenience method to get this element as a primitive short value.
     *
     * @return get this element as a primitive short value.
     * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid
     * short value.
     * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains
     * more than a single element.
     */
    public short getAsShort() {
      throw new UnsupportedOperationException(getClass().getSimpleName());
    }
  
    /**
     * Returns a String representation of this element.
     */
    @Override
    public String toString() {
      try {
        StringWriter stringWriter = new StringWriter();
        JsonWriter jsonWriter = new JsonWriter(stringWriter);
        jsonWriter.setLenient(true);
        Streams.write(this, jsonWriter);
        return stringWriter.toString();
      } catch (IOException e) {
        throw new AssertionError(e);
      }
    }
  }
  