随机字符生成器

MyRandomran=newMyRandom();System.out.println(ran.nextString(1));System.out.println(ran.nextString(50,OnlyNum));System.out.println(ran.nextString(50,OnlyBig));System.out.println(ran.nextString(50,OnlySmall));System.out.println(ran.nextString(50,MyRandom.NumAndSmall));System.