Java - Large array advice on how to break it down

Question

I hope you're doing good. I was making the code for a program that will be dealing with a large number of array elements. For example, array A[] will have all the words that start with a letter "a". Now, if i put all in one class the program can't run due to not enough memory. I was going to make each array its own class. But in general, is there a better way to approach this instead of arrays? Or any other advice to wrestle with the many elements? I might be looking at 500k-1.xmil elements in the whole thing. Thank you in advance!