错误The operator != is undefined for the argument type(s) long, null

此处报错 if (users.getUsersid() != null)
The operator != is undefined for the argument type(s) long, null

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private long usersid; 

public long getUsersid() { 

 return this.usersid; 

 }

应该是Long
改正之后

private Long usersid; 

public Long getUsersid() { 

 return this.usersid; 

 }