code: public static boolean equal(Object obj1, Object obj2) {
  //		return (obj1 != null) ? (obj1.equals(obj2)) : (obj2 == null);
  		return (obj1 == obj2) || (obj1 != null && obj1.equals(obj2));
  	}
docs: 比较两个对象是否相等。<br>
  相同的条件有两个，满足其一即可：<br>
  <ol>
  <li>obj1 == null &amp;&amp; obj2 == null</li>
  <li>obj1.equals(obj2)</li>
  </ol>
  1. obj1 == null &amp;&amp; obj2 == null 2. obj1.equals(obj2)
  
  @param obj1 对象1
  @param obj2 对象2
  @return 是否相等