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：
& C# K9 ]: n7 s$ a9 k6 f# T7 vERROR [main] 21:46:56,324 saf.core.runtime.Boot - null
java.lang.NullPointerException
        at saf.core.runtime.Boot.init(Boot.java:79)
# D1 Z1 q( t! ~) Y  ~        at saf.core.runtime.Boot.main(Boot.java:250)
6 l( H% h6 `& e' N0 z. v6 Q( Q        at repast.simphony.runtime.RepastMain.main(RepastMain.java:43)
6 X1 q4 H) P" g5 \% ~2 C, {9 q; aERROR - null
/ X6 Z* s; `  }6 t; ~java.lang.NullPointerException
( Z% ~+ @" x4 r9 a7 H: P        at saf.core.runtime.Boot.init(Boot.java:79)
7 L. T" E+ U8 d& n; w7 r+ |        at saf.core.runtime.Boot.main(Boot.java:250)
& A: z- `/ `: u7 l0 m        at repast.simphony.runtime.RepastMain.main(RepastMain.java:43)
ERROR [main] 21:46:56,397 saf.core.runtime.Boot - null
& V) w7 v, U' W3 }java.lang.NullPointerException
; [6 s- n& P, Z% t        at saf.core.runtime.Boot.run(Boot.java:105)
7 X, y. F1 y: Q6 m. l4 T* N+ F        at saf.core.runtime.Boot.main(Boot.java:251)
6 j0 ^: P% q1 g% Y0 q" J; @- `        at repast.simphony.runtime.RepastMain.main(RepastMain.java:43)
ERROR - null
. f+ b0 P( T! ]8 [java.lang.NullPointerException
        at saf.core.runtime.Boot.run(Boot.java:105)
        at saf.core.runtime.Boot.main(Boot.java:251)
        at repast.simphony.runtime.RepastMain.main(RepastMain.java:43)
; u4 B$ M2 r& t请问怎么解决哇，谢谢各位