CODEWITHSUNDEEP
javafor-loopnested-loops
Mike
Mike

Reputation: 2339

Nested loops for specific numbers

I have a method that takes in 2 ints method(int ii, int xx). I want to loop through a range of values but I cant think of a way to do it without hard coding each value.

When ii = 21, i want xx = 19 through 9 when ii = 20, i want xx = 18 through 12

so hard coded it would be:

method(21,19)
method(21,18)
...
method(21,10)
method(21,9)
method(20,18)
method(20,17)
...
method(20,13)
method(20,12)

this is what i have so far but it doesnt handle spcific cases like i dont want it to do method(4,19)

            for(int ii = 9;ii<21;ii++){
                for(int xx = 4;xx<19;xx++){
                    method(ii,xx);
                }
            }

Upvotes: 0

Views: 250

Answers (2)

Kevin K
Kevin K

Reputation: 9584

As originally suggested by Edd, you'll want to use a map. I suggest creating a Range class to represent an integer range for the xx values, then you can build a map of Integer --> Range (ii --> xx):

static class Range {
    public final int start;
    public final int end;

    public Range(int start, int end) {
        this.start = start;
        this.end = end;
    }
}

static final Map<Integer,Range> RANGE_MAP = new HashMap<Integer,Range>();
static {
    RANGE_MAP.put(21, new Range(9,19));
    RANGE_MAP.put(20, new Range(12,18));
    // ...
}

void calling_method() {
    for(Entry<Integer,Range> entry : RANGE_MAP.entrySet()) {
        int ii = entry.getKey();
        Range r = entry.getValue();
        for(int xx = r.start; xx <= r.end; xx++){
            method(ii,xx);
        }
    }
}

void method(int ii, int xx) {
    // do stuff
}

Upvotes: 2

Edd
Edd

Reputation: 8570

It is hard coded but a list in a map could do this for you:

private static final Map<Integer,List<Integer>> map = new HashMap<Integer,List<Integer>>(){{
    put(21, new ArrayList<Integer>(){{
        add(19);
        add(18);
        add(17);
        ...
    }});
    put(20, new ArrayList<Integer>(){{
        add(18);
        add(17);
        ...
    }});
}};

Holding the map as static and final will mean you're not creating it each time you're using it.

Then you can loop through like so:

for(Integer ii : map.keySet()){
    for(Integer xx : map.get(ii)){
        method(ii,xx);
    }
}

Upvotes: 0

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