.equals（）和==在Java上整数（==工作但.equals没有!!）(.equals() and == in Java on Integer (== worked but .equals did not!!))

 码： 
 
call.getUserId().equals(ITConstants.SPECIALID)

public static final Integer SPECIALID= 0;
 
 POJO： 
 
public class ImCall implements java.io.Serializable {
private Integer userId;
 
 HBM： 
 
<property name="userId">
  <column name="USER_ID" />
</property>
 
 MySQL的： 
 
int(11) is the datatype in MySQL
 
 当UserId为零时“.equals（）”不起作用（返回false）但令人惊讶的是“==”工作（返回true）。 我以为是因为Tomcat Server中的一些问题。所以我清理它并重新启动。 仍然是同一个问题。 
 
 但是几天后，我上面提到的问题再次出现了。 但现在，==和.equals（）都有效！ 
 
 所以，我的第一个问题是，当“==”有效并且“.equals（）”没有时，是否存在任何情况。 第二个问题是，为什么“==”在这种情况下返回true？ 
 
 编辑： 
 
 Getters仅返回Integer。 
 
public Integer getUserId() {
    return userId;
}

public void setUserId(Integer userId) {
    this.userId = userId;
}

Code:
 
call.getUserId().equals(ITConstants.SPECIALID)

public static final Integer SPECIALID= 0;
 
POJO:
 
public class ImCall implements java.io.Serializable {
private Integer userId;
 
HBM:
 
<property name="userId">
  <column name="USER_ID" />
</property>
 
MySQL:
 
int(11) is the datatype in MySQL
 
When UserId was zero ".equals()" did not work(returned false) but surprisingly "==" worked(returned true). I thought it was because of some problem in Tomcat Server.So I cleaned it and restarted. Still the same issue.
 
But again after a couple of days,the problem I mentioned above did not reoccur. But now,both == and .equals() works!
 
So,my 1st question is,is there any situation when "==" works and ".equals()" does not. 2nd question is,Why "==" returns true in this case?
 
Edit : 
 
Getters return Integer only.
 
public Integer getUserId() {
    return userId;
}

public void setUserId(Integer userId) {
    this.userId = userId;
}

原文：https://stackoverflow.com/questions/20718592