在看Thinking in Java，有一段实在没看懂

package com.company.allAreTheObjective.Symbol; import java.util.*; /** * Created by Francis on 12/05/2016. */ public class VowelsAndConsonants { public static void main(String args[]){ Random rand = new Random(47); for (int i = 0; i < 100; i++){ int c = rand.nextInt(26) + 'a'; System.out.print((char)c+","+ c +":"); switch(c){ case 'u' : System.out.println("vowel");break; case 'w' : System.out.println("Sometimes a vowel");break; default : System.out.println("constant"); } } } }

这一段为什么输出恒为
y,121:constant
n,110:constant
z,122:constant
b,98:constant
r,114:constant
n,110:constant
y,121:constant