Looping Over Real Test Data

A counter is useful, but the everyday job is looping over a set of values — passwords, browsers, rows. You hold many values in an array (you met String[] args in Chapter 1). Here it does real work:

public class L2 {
    public static void main(String[] args) {
        String[] passwords = {"", "123", "password", "admin", "P@ss!"};
        for (int i = 0; i < passwords.length; i++) {
            System.out.println("Attempt " + (i + 1) + ": trying '" + passwords[i] + "'");
        }
        System.out.println("Total attempts: " + passwords.length);
    }
}

Attempt 1: trying ''
Attempt 2: trying '123'
Attempt 3: trying 'password'
Attempt 4: trying 'admin'
Attempt 5: trying 'P@ss!'
Total attempts: 5

Three details worth noticing:

1. The counter starts at 0, not 1 — array positions in Java are numbered from zero: the first item is passwords[0], the fifth is passwords[4].
2. The condition uses passwords.length, the count of items — so the same loop works for five passwords or five hundred, with no edit.
3. passwords[i] reads the item at position i. You wrote i + 1 only to print a human-friendly "Attempt 1" instead of "Attempt 0".

You are using arrays here before they are fully explained. That is on purpose — loops and arrays are easier to learn together. The full treatment is Chapter 5. Until then: an array is a numbered row of boxes, counted from zero, and .length tells you how many.

For each: when you do not need the index

There is a cleaner way to say "do this for every item" when you do not need the position number — the enhanced for, often read aloud as "for each":

public class L3 {
    public static void main(String[] args) {
        String[] browsers = {"chrome", "firefox", "edge"};
        for (String browser : browsers) {
            System.out.println("Launching " + browser);
        }
    }
}

Launching chrome
Launching firefox
Launching edge

Read the header as "for each browser in browsers." No counter, no condition, no [i] — Java walks the array and hands you one item each pass. Use this form whenever you want every item and do not care about its index; use the counted form when you need the position, or when you are not walking an array at all.

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You can drive a password list and a browser list through one loop shape. The next lesson is for when you cannot answer "how many times?" — only "until what?": while and do-while, the shapes behind retries and polls.