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
/ E4 O- w5 e4 z* h# cjava.lang.NullPointerException
        at saf.core.runtime.Boot.init(Boot.java:79)
        at saf.core.runtime.Boot.main(Boot.java:250)
( D" {' d  S$ L: ]- @1 U7 B        at repast.simphony.runtime.RepastMain.main(RepastMain.java:43)
5 [' Z% q! d3 Q* g( n. r% QERROR - null
) g5 n9 M0 z8 d) X* vjava.lang.NullPointerException
        at saf.core.runtime.Boot.init(Boot.java:79)
        at saf.core.runtime.Boot.main(Boot.java:250)
/ X1 i! ^1 E9 ~" Z  x        at repast.simphony.runtime.RepastMain.main(RepastMain.java:43)
) {; J9 [9 z( V" v. dERROR [main] 21:46:56,397 saf.core.runtime.Boot - null
java.lang.NullPointerException
        at saf.core.runtime.Boot.run(Boot.java:105)
1 [7 F$ Z& o+ K: Y1 J7 N        at saf.core.runtime.Boot.main(Boot.java:251)
4 B5 g' f5 z8 Q0 m! O/ L        at repast.simphony.runtime.RepastMain.main(RepastMain.java:43)
ERROR - null
java.lang.NullPointerException
! t) h( k4 j5 V7 N; O* p+ N" v        at saf.core.runtime.Boot.run(Boot.java:105)
        at saf.core.runtime.Boot.main(Boot.java:251)
( u2 @' Y. ~3 L" c- m        at repast.simphony.runtime.RepastMain.main(RepastMain.java:43)
请问怎么解决哇，谢谢各位