Java conditions, arrays, and loops

Count values that satisfy a boundary condition.

Java

class Main {
    public static void main(String[] args) {
        int[] scores = {49, 50, 80};
        int passed = 0;
        for (int score : scores) {
            if (score >= 50) passed++;
        }
        System.out.println(passed);
        if (passed != 2) throw new AssertionError("count");
    }
}

Output

Explanation

An enhanced for loop visits each array element. A comparison produces a boolean used by if to decide whether the counter changes.

The >= condition includes a score exactly equal to the pass threshold. The array has a fixed length; the loop reads its elements without changing them.

Explore the dry run

Guided walkthroughReady

1class Main {

2 public static void main(String[] args) {

3 int[] scores = {49, 50, 80};

4 int passed = 0;

5 for (int score : scores) {

6 if (score >= 50) passed++;

7 }

8 System.out.println(passed);

9 if (passed != 2) throw new AssertionError("count");

10 }

11}

Follow the example

Start to inspect the source, values, and output. These prepared steps explain the published sample; grouped loop steps describe multiple iterations.

View the complete dry-run table

Prepared trace of the published program. Some rows group repeated iterations.
What happens	State after step	Output so far
Create an array of three scores.	`scores = [49, 50, 80]`	—
Initialize the counter.	`passed = 0`	—
49 fails; 50 passes at the boundary.	`passed = 1`	—
80 also passes.	`passed = 2`	—
Print the final count.	`passed = 2`	2

Cost and common mistakes

O(n) time and O(1) auxiliary space.

Replacing >= with > would exclude score 50.
Changing the copied loop variable does not change the array's primitive element.

Try it yourself

Add score 0 and score 100.

Reveal answer and reasoning

The count becomes 3 because only 100 adds another passing score.

Java conditions, arrays, and loops

Explanation

Follow the example

Cost and common mistakes

Try it yourself

Further reading