当包类进入dex时我得到一个错误。我可以解决它吗？

Question

当我使用ant将类封装到dex文件中时出错。

-dex:
   [echo] Converting compiled files and external libraries into bin/classes.dex...
   [apply] UNEXPECTED TOP-LEVEL ERROR:
   [apply] java.io.FileNotFoundException: bin\classes.dex
   [apply]  at java.io.FileOutputStream.open(Native Method)
   [apply]  at java.io.FileOutputStream.<init>(Unknown Source)
   [apply]  at java.io.FileOutputStream.<init>(Unknown Source)
   [apply]  at com.android.dx.command.dexer.Main.openOutput(Main.java:708)
   [apply]  at com.android.dx.command.dexer.Main.run(Main.java:239)
   [apply]  at com.android.dx.command.dexer.Main.main(Main.java:174)
   [apply]  at com.android.dx.command.Main.main(Main.java:95)