意思不相同。in class这个词组的意思是“在课堂上；上课中”，侧重强调的是上课。in the class这个词组的意思是“在班级里”，不强调上课或在课堂上。class意思是班；班级；课；上课；(某科目的)系列课程。
in class例句
We are required to speak English in class.
上课时要求我们说英语。
Tom was admonished for chewing gum in class.
汤姆在课堂上嚼口香糖，受到了告诫。
My Chinese teacher loves to tell jokes in class.
我的语文老师喜欢在课堂上讲笑话。
in the class例句
There is an equal number of boys and girls in the class.
这个班男女生人数相等。
Tom is probably the brightest student in the class.
汤姆大概是班里最聪明的学生。
Everyone in the class seemed eager to learn.
班上每个人似乎都热爱学习。
