用instanceof类型转换是不是只能转换一个对象？

     Jiaoche jiaoche = new Jiaoche();

feiji plane = new feiji();

    Jiaotonggongju jiaotonggongju = jiaoche;

if(jiaotonggongju instanceof feiji) {

feiji plane2 = (feiji) jiaotonggongju;

}else {

System.out.println("123");

}

if(jiaotonggongju instanceof Jiaoche) {

Jiaoche jiaoche2 = (Jiaoche)jiaotonggongju;}

else {System.out.println("321");}

这样子只能转换Jiaoche，feiji就转换不了了，当我两种都转换的时候就报错了