如何匹配逗号分隔字符串列表中的确切字符串值

Question

我有大约100万条记录。这类似于

之类的数组

String[] a1 =  {"A,B,C","C,D,E",...so on};
String[] a2 =  {"F,G,H","I,J,K",...so on};
.
.
.
String[] ax =  {"X1,X2,X3","X4,X5,X6",...so on}; //x is near to one million.

如果字符串数组包含特定字，即A或B，最好的方法是什么？