Thread: Learning - could someone explain this code to me?

class Passer {
 
    void toUpperCase(String[] text) {
        for (int i = 0; i < text.length; i++) {
            text[i] = text[i].toUpperCase();
        }
    }
 
    public static void main(String[] arguments) {
        Passer passer = new Passer();
        passer.toUpperCase(arguments);
        for (int i = 0; i < arguments.length; i++) {
            System.out.print(arguments[i] + " ");
        }
        System.out.println();
    }
}

Can someone explain this code to me? I'm not quite sure I understand. This is what I'm thinknig...

From what I can understand here the toUpperCase method takes a string of text, and converts it into an array. It then loops through the entire array, turning each letter into an uppercase using this. text[i] = text[i].toUpperCase();


In the second method, called main, a string from the command-line arguments is taken and put into an array. an object called passer is created that references the upperCase method. and then from here I'm not exactly quite sure what is going on.

I see that the for loop in the main method is looping through the length of the argument string, turning each into an uppercase, but I'm not exactly sure why it works.

The void in the first method is confusing me. doesn't void mean that nothing gets returned? If nothing is getting returned, how is the main method able to get the capitalized letters from the toUpperCase method?

A few notes, for clarity:

You can see that an array of String objects is being used, not a single String. The main method is called first, and given an array of Strings. Then the Strings are modified a String at a time, not a character at a time.

As far as the method return value of void, java passes the array of strings to the method by reference, a pointer, or the address of where the array is. The method modifies the array, not a copy sent over.
Search keywords: "java pass by value" "java pass by reference"
Be sure to note the way primitives are treated vs the way objects are treated.

Hi, I think I understand what youre saying. The toUppercase method is void because it is not returning anything back to main. The way it is converting the strings to uppercase is via a direct reference. It is literally going into the strings and converting it to uppercase. Is this the correct way to think about it?