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public static int multAccum(int oldAcc, int newVal, int scale) {
// May result in overflow
return oldAcc + (newVal * scale);
}
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public static int multAccum(int oldAcc, int newVal, int scale) throws ArithmeticException {
preMultiply(newVal, Scale);
final int temp = newVal * scale;
preAdd(oldAcc, temp);
return oldAcc + temp;
}
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For all integral types other than long, the next larger integral type can represent the result of any single integral operation. For example, operations on values of type int can be safely performed using type long. As a result, we can perform an operation using the larger type and range-check before downcasting down casting to the original type. Note, however, that this guarantee holds only for a single arithmetic operation; larger expressions without per-operation bounds checking may overflow the larger type.
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public static long intRangeCheck(long value) throws ArithmeticOverflow {
if ((value < Integer.MIN_VALUE) || (value > Integer.MAX_VALUE)) {
throw new ArithmeticException("Integer overflow");
}
return value;
}
public static int multAccum(int oldAcc, int newVal, int scale) throws ArithmeticException {
final long res =
intRangeCheck(((long) oldAcc) + intRangeCheck((long) newVal * (long) scale));
return (int) res; // safe down-cast
}
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private static final BigInteger bigMaxInt = BigInteger.valueOf(Int.MAX_VALUE);
private static final BigInteger bigMinInt = BigInteger.valueOf(Int.MIN_VALUE);
public static BigInteger intRangeCheck(BigInteger val) throws ArithmeticException {
if (val.compareTo(bigMaxInt) == 1 ||
val.compareTo(bigMinInt) == -1) {
throw new ArithmeticException("Integer overflow");
}
return val;
}
public static int multAccum(int oldAcc, int newVal, int scale) throws ArithmeticException {
BigInteger product =
BigInteger.valueOf(newVal).multiply(BigInteger.valueOf(scale));
BigInteger res = intRangeCheck(BigInteger.valueOf(oldAcc).add(product));
return res.intValue(); // safe conversion
}
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