public class studenttest
{
    public static void main (String[] args)
    {
    studenttest tom = new studenttest(/*"Tom","200202410"*/);
    tom.setstudentname("Tom");
    tom.setstudentnumber("200202410");
    tom.setstudentsex("man");
    tom.setstudentaddress("American");
    tom.setstudentbirthday("1990.07.24");
    tom.setstudentspeciality("电子信息科学与技术");
    System.out.println(tom.toString());
 }


/*class student
{*/
    private String Strname;//学生姓名
    private    String Strnumber;//学号
    private String Strsex;//性别
    private String Strbirthday;//出生年月
    private String Strspeciality;//专业
    private String Straddress;//地址


/*public student(String name,String number)
{
    Strname=name;
    Strnumber=number;
}
*/
/*public String getstudentname()
{
    return Strname;
}*/

public void setstudentname(String name)
{
     Strname=name;
}

/*public String getstudentnumber()
{
     return Strnumber;
}
*/

public void setstudentnumber(String number)
{
     Strnumber=number;
}


/*public String getstudentsex()
{
    return Strsex;
}*/

public void setstudentsex(String sex)
{
     Strsex=sex;
}

/*public String getstudentbirthday()
{
    return Strbirthday;
}
*/
public void setstudentbirthday(String birthday)
{
     Strbirthday=birthday;
}

/*public String getstudentspeciality()
{
    return Strspeciality;
}
*/
public void setstudentspeciality(String speciality)
{
 Strspeciality=speciality;
}

/*public String getstudentaddress()
{
    return Straddress;
}*/

public void setstudentaddress(String address)
{
     Straddress=address;
}

public String toString()
{
     String information=" ";/*= "学生姓名=" + Strname + ",学号=" +Strnumber;*/
     if( !Strname.equals(""))
        information += "姓名=" + Strname;
     if( !Strnumber.equals(""))
        information += ",学号=" + Strnumber;
     if( !Strsex.equals(""))
        information += ",性别=" + Strsex;
     if( !Strbirthday.equals(""))
        information += ",出生年月=" + Strbirthday;
     if( !Strspeciality.equals(""))
        information += ",专业=" + Strspeciality;
     if( !Straddress.equals(""))
        information += ",籍贯=" + Straddress;   
        
     return information;
}
}
 

帮忙看下
if( !Strname.equals("") )
   information += "姓名=" + Strname;
里的!Strname.equals("")什么意思
本人菜鸟，求大侠赐教，谢谢

.equals() 的意思就是判断字符串是否相等的方法。
比如：Strname.equals("")
因为  private String Strname;//学生姓名
所以 这个意思就是判断你的学生姓名是不是为空（""）