编写非静态方法作为静态方法

Question

I'm trying to write this method as a static method but I don't fully understand how static methods work past them not creating objects to work with.

This is the method I'm trying to convert

public void process(String str)
{
    for (int i=0; i<str.length(); i++){
        char letter = str.charAt(i);
        int index = Character.toLowerCase(letter-'a');
        if (index>=0 && index<26){
            counts[index]++;
        }
    }
}

This method just takes a string and records the number of times each letter showed up in the String

Im trying to write this as a static method and I have this method stub

public static LetterCounter buildCounter(String str)
{

}

Answer 1

Since this is a learning exercise, I wouldn't write any code, but describe what needs to be done:

1. Create a new instance of LetterCounter
2. Call an instance method process on it, passing str that you got in your buildCounter
3. Return the instance of LetterCounter that you created in step 1.

You are done!

Answer 2

Your current code would require that counts[] be declared as static also, meaning there is only one counts[], and every time you call MyClass.process("blah") it would increase the class variable counts[index]

I am guessing but I think what you are trying to do is create a static "utility' function to return an array of counts for the various charactors in the passed in string? So something similar to this (untested) code. then you would call something like MyUtilClass.process("xxyz"); In this case "static" means that the process does is not associated with an object, it is more like a "function" or "subroutine"

public static int[] process(String str) {
    int[] counts = new int[25];
    for (int i=0; i<str.length(); i++){
        char letter = str.charAt(i);
        int index = Character.toLowerCase(letter-'a');
        if (index>=0 && index<26){
            counts[index]++;
        }
    }
 return counts;
}