Generate Possion Dis.
step1:Generate a random number between [0,1]
step2:Let u=F(x)=1-[(1/e)x]
step3:Slove x=1/F(u)
step4:Repeat Step1~Step3 by using different u,you can get x1,x2,x3,...,xn
step5:If the first packet was generated at time [0], than the
second packet will be generated at time [0+x1],The third packet will be generated at time [0+x1+x2],
and so on ….
Random-number generation
1.static method random from class Math
-Returns doubles in the range 0.0 <= x < 1.0
2.class Random from package java.util
-Can produce pseudorandom boolean, byte, float, double, int, long and Gaussian values
-Is seeded with the current time of day to generate different sequences of numbers each time the program executes
