How to use array correctly

Question

I'm trying to initialize an array and insert some values into it in Java, but I get out of bounds exception. This is the code

int xPoints[] = new int[]{};
int i = 0;
for(Edge e : myVectorOfEdges){
    xPoints[i] = e.start;
    i++;

}

I must use this type of data structure, because I am working with polygons which accept only int[] type.

Your initialization of xPoints is incorrect. Try this: http://stackoverflow.com/questions/363681/generating-random-integers-in-a-specific-range — gtwd, May 08 '16 at 20:13
@Andrew it's Edge type, a class which created, it stores start and end point indexes in it — Keselme, May 08 '16 at 21:03

score 2 · Answer 1 · answered May 08 '16 at 20:13

2

You have initialized xPoints as an empty array, so any attempt to access one of its (non-existent) elements will result in an ArrayIndexOutOfBoundsException. Instead, you should initialize it to the same size as myVectorOfEdges which you are iterating:

int xPoints[] = new int[myVectorOfEdges.length];

answered May 08 '16 at 20:13

Mureinik

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The problem with this implementation is the length on the vector is much larger than I actually need to use, because it contains all edges from my input file, while I need to iterate through it and look for polygons, and than create xPoints[] for each polygon I find – Keselme May 08 '16 at 21:06

score 1 · Answer 2 · answered May 08 '16 at 20:10

1

int xPoints[] = new int[myVectorOfEdges.length];
    int i = 0;
    for(Edge e : myVectorOfEdges){
        xPoints[i] = e.start;
        i++;

    }

answered May 08 '16 at 20:10

Oussema Aroua

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score 0 · Answer 3 · answered May 08 '16 at 20:13

0

Just use the slow version:

    int[] xPoints = myVectorOfEdges.stream().mapToInt(e -> e.start).toArray();

answered May 08 '16 at 20:13

Tassos Bassoukos

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are you sure that `myVectorOfEdges` is not an array? – Andrew Tobilko May 08 '16 at 20:26

How to use array correctly

3 Answers3