用java命令运行程序为何出错？而jbuilder可正常运行？javaw和java的区别是什么？

有源程序（全文）：
import java.io.*;
public class PassTest{
float ptValue;
public static void main(String args[]){
int val;
PassTest pt=new PassTest();
val=11;
System.out.println("Original Int Value is :"+val);
pt.changeInt(val);
System.out.println("Int Value after Change is :"+val);
pt.ptValue=101f;
System.out.println("Original ptValue is:"+pt.ptValue);
pt.changeObjValue(pt);
System.out.println("ptValue after Change is:"+pt.ptValue);
}
public void changeInt(int value){
value=55;
}
public void changeObjValue(PassTest ref){
ref.ptValue=99f;
}
}
然后用javac 编译得到passtess.class,
在cmd中用java passtess.class运行确却有错误提示：
“Exception in thread "main" java.lang.NoClassDefFoundError: passtest/java"
而在jbuilder中运行却得到正确的结果：
Original Int Value is :11
Int Value after Change is :11
Original ptValue is:101.0
ptValue after Change is:99.0
郁闷呀！