repast运行出现java.lang.NullPointerException，怎么解决呢

silviasong

在对repastS中已有仿真例子运行中，会出现java.lang.NullPointerException，然后就运行不了了：
ERROR [main] 21:46:56,324 saf.core.runtime.Boot - null
) [" y! W  C/ rjava.lang.NullPointerException
        at saf.core.runtime.Boot.init(Boot.java:79)
4 T$ S: W# l, N. A        at saf.core.runtime.Boot.main(Boot.java:250)
0 q3 @! ~  t8 b, V/ m        at repast.simphony.runtime.RepastMain.main(RepastMain.java:43)
7 l3 L& d- ]7 ~- r. uERROR - null
/ K7 L1 E! {2 C) x! i6 Ujava.lang.NullPointerException
        at saf.core.runtime.Boot.init(Boot.java:79)
+ q8 R$ K' Y$ x- H% I3 d        at saf.core.runtime.Boot.main(Boot.java:250)
  ^* W9 `1 \+ [  E        at repast.simphony.runtime.RepastMain.main(RepastMain.java:43)
ERROR [main] 21:46:56,397 saf.core.runtime.Boot - null
' u6 w9 o9 o" K( d: P3 Zjava.lang.NullPointerException
        at saf.core.runtime.Boot.run(Boot.java:105)
! e) {1 M1 Z% u" X; d        at saf.core.runtime.Boot.main(Boot.java:251)
        at repast.simphony.runtime.RepastMain.main(RepastMain.java:43)
* p, h! @: m+ K! S: ~2 n: f7 m; T. `ERROR - null
java.lang.NullPointerException
        at saf.core.runtime.Boot.run(Boot.java:105)
" u3 U. j! h7 ]5 u+ K( s' ?$ |        at saf.core.runtime.Boot.main(Boot.java:251)
  _8 J* w! h0 Q' c; O! T1 {        at repast.simphony.runtime.RepastMain.main(RepastMain.java:43)
请问怎么解决哇，谢谢各位