I would like to ask a simple question but seems to be complex if we talk in context of Apex programming. Like in java we have a simple method to get the array of characters by using

public char[] toCharArray(): String

Do we have such kind of provision or some kind of custom logic to define not much complex without making use of subString() method in Apex?

EDIT: I would like to convert a String "banana" such that each of its characters can be manipulated.