It worth nothing that BigInteger and BigDecimal are Number's.

[GoogleCodeExporter]

These Numbers can have overflow and rounding errors if converted to an int
value.  A double is the safest default choice. (Even for long it should be
fine.)

The following program prints
forConstantValue(-1) is NEVER
forConstantValue2(-1) is NEVER
forConstantValue(-0.1) is ALWAYS // rounded to 0.
forConstantValue2(-0.1) is NEVER
forConstantValue(-9999999999) is NEVER
forConstantValue2(-9999999999) is NEVER
forConstantValue(-999999999999) is ALWAYS // overflow to a postive number.
forConstantValue2(-999999999999) is NEVER
forConstantValue(9999999999) is ALWAYS
forConstantValue2(9999999999) is ALWAYS
forConstantValue(999999999999) is NEVER // overflow to a negative number.
forConstantValue2(999999999999) is ALWAYS
forConstantValue(NaN) is ALWAYS // Is not signed e.g. should fail @Signed test.
forConstantValue2(NaN) is UNKNOWN

public static void main(String... args) {
    for (Number n : new Number[]{
            new BigDecimal("-1"),
            new BigDecimal("-0.1"),
            new BigInteger("-9999999999"),
            new BigInteger("-999999999999"),
            new BigInteger("9999999999"),
            new BigInteger("999999999999"),
            Double.NaN,
    }) {
        System.out.println("forConstantValue(" + n + ") is " +
forConstantValue(n));
        System.out.println("forConstantValue2(" + n + ") is " +
forConstantValue2(n));
    }
}

// from Nonnegative
public static When forConstantValue(Object v) {
    if (!(v instanceof Number))
        return When.NEVER;
    boolean isNegative;
    Number value = (Number) v;
    if (value instanceof Long)
        isNegative = value.longValue() < 0;
    else if (value instanceof Double)
        isNegative = value.doubleValue() < 0;
    else if (value instanceof Float)
        isNegative = value.floatValue() < 0;
    else
        isNegative = value.intValue() < 0;

    if (isNegative)
        return When.NEVER;
    else
        return When.ALWAYS;
}

public static When forConstantValue2(Object v) {
    if (!(v instanceof Number))
        return When.NEVER;

    double value = ((Number) v).doubleValue();
    if (Double.isNaN(value))
        return When.UNKNOWN;
    else
        return value < 0 ? When.NEVER : When.ALWAYS;
}

> What steps will reproduce the problem?
1. run the program above 

> What is the expected output? 
forConstantValue2

> What do you see instead?
In valid conversion of BigInteger and BigDecimal

Original issue reported on code.google.com by peter.la...@gmail.com on 27 Jan 2009 at 5:49