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In this noncompliant code example, the integer hashKey references an element of the hash array. However, as the hash key is not guaranteed to be positive, the lookup function may fail, triggering a java.lang.ArrayIndexOutOfBoundsException on all negative inputs.

private int SIZE = 16;	
public int[] hash = new int[SIZE];
	
public int lookup(int hashKey) {
  return hash[hashKey % SIZE];
}

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This compliant solution calls a method that returns a modulus that is always positive.

// method imod() gives non-negative result
private int SIZE = 16;
public int[] hash = new int[SIZE];

private int imod(int i, int j) {
  return (i < 0) ? ((-i) % j) : (i % j);
}
	
public int lookup(int hashKey) {
  return hash[imod(hashKey, size)];
}

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Alternatively, an explicit range check must be performed on the numerator at every susceptible point as demonstrated in this compliant solution.

public int lookup(int hashKey) {
  if (hashKey < 0)
    return hash[(-hashKey) % size];
  return hash[hashKey % size];
}

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