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Dahua ICC Open API SDK for Java

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package com.dahuatech.hutool.json;

import java.io.Serializable;

/**
 * 用于定义null，与Javascript中null相对应

 * Java中的null值在js中表示为undefined。
 *
 * @author Looly
 */
public class JSONNull implements Serializable {
  /**
   * NULL 对象用于减少歧义来表示Java 中的null 

   * NULL.equals(null) 返回 true. 

   * NULL.toString() 返回 "null".
   */
  public static final JSONNull NULL = new JSONNull();
  private static final long serialVersionUID = 2633815155870764938L;

  /**
   * There is only intended to be a single instance of the NULL object, so the clone method returns
   * itself. 克隆方法只返回本身，此对象是个单例对象
   *
   * @return NULL.
   */
  @Override
  protected final Object clone() {
    return this;
  }

  /**
   * A Null object is equal to the null value and to itself. 对象与其本身和null值相等
   *
   * @param object An object to test for nullness.
   * @return true if the object parameter is the JSONObject.NULL object or null.
   */
  @Override
  public boolean equals(Object object) {
    return object == null || object == this;
  }

  @Override
  public int hashCode() {
    return super.hashCode();
  }

  /**
   * Get the "null" string value. 获得“null”字符串
   *
   * @return The string "null".
   */
  @Override
  public String toString() {
    return "null";
  }
}