Recieve element and moving pointers in 2D array (Java)

Question

I'm a beginner in Java, and I need to write a next() method, which will return current value from 2D array and move pointer to the next element. It's similar to Iterators's next() method.

For example, we may have:

int[][] values = {{1, 2}, {3, 4}};

When we are using next() at the first time, it returns 1 (pointer moved to next index, now pointer stands at 2), second use - 2(+move of pointer), third - 3(+move pointer), etc.

I wrote some bad code to illustrate what I want to do:

public class ArrayConverter {
    private final int[][] values;
    private int upper = 0;
    private int lower = -1;

    public ArrayConverter(int[][] values) {
        this.values = values;
    }

    public int next() {
        lower++;
        int result = 0;
        try {
            result = values[upper][lower];
        } catch (ArrayIndexOutOfBoundsException a) {
            lower = 0;
            upper++;
            try {
                result = values[upper][lower];
            } catch (ArrayIndexOutOfBoundsException r) {
                upper = 0;
                lower = -1;
                System.out.print("Reached the end of data. Indexes will be zeroed.");
            }
        }
        return result;
    }
}

Are there any ways to do it better, especially without using try/catch blocks?

You should never catch an ArrayIndexOutOfBoundsException, just check whether the index is within bounds beforehand. — KarelPeeters
– KarelPeeters, Commented Feb 1, 2017 at 8:14
codereview.stackexchange.org is a better place to submit code fragments for improvement / suggestions — tucuxi
– tucuxi, Commented Feb 1, 2017 at 11:00
@tucuxi I'm pretty sure you mean codereview.stackexchange.**com** ... — Vogel612
– Vogel612, Commented Feb 1, 2017 at 11:03

Tobias G · Accepted Answer · 2017-02-01 08:17:23Z

1

Use array.length for range checks

Try this:

private int upper = 0;
private int lower = 0;

public int next() {
    if(lower >= values[upper].length){
        upper++;
        lower = 0;
    }
    if(upper >= values.length){
        throw new NoSuchElementException("Reached end");
    }
    int result = values[upper][lower++];
    return result;
}

answered Feb 1, 2017 at 8:17

Tobias G

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Recieve element and moving pointers in 2D array (Java)

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Use array.length for range checks

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