为什么在Spring Boot framework源代码中将"Number"转换为"Float"或"Double"时不检查范围溢出

Question

请查看来自org.springframework.util.NumberUtils#convertNumberToTargetClass()的源代码片段，方法签名是+ <T extends Number> T convertNumberToTargetClass(number:Number, targetClass:Class<?>)

public static <T extends Number> T convertNumberToTargetClass(Number number, Class<T> targetClass)
            throws IllegalArgumentException {
    ... ...
    ... ...
    else if (Float.class == targetClass) {
        return (T) Float.valueOf(number.floatValue());
    }
    .... ....
    .... ....
}

将number转换为Float时，不检查number是否超出Float的范围。但它会检查将数字转换为 Byte、Integer 或 Short 时，如下所示：

    public static <T extends Number> T convertNumberToTargetClass(Number number, Class<T> targetClass)
            throws IllegalArgumentException {
        ... ...
        ... ...
        else if (Byte.class == targetClass) {
            long value = checkedLongValue(number, targetClass);
            if (value < Byte.MIN_VALUE || value > Byte.MAX_VALUE) {
                raiseOverflowException(number, targetClass);
            }
            return (T) Byte.valueOf(number.byteValue());
        }
        ... ...
        ... ...
    }

    private static long checkedLongValue(Number number, Class<? extends Number> targetClass) {
        BigInteger bigInt = null;
        if (number instanceof BigInteger) {
            bigInt = (BigInteger) number;
        }
        else if (number instanceof BigDecimal) {
            bigInt = ((BigDecimal) number).toBigInteger();
        }
        // Effectively analogous to JDK 8's BigInteger.longValueExact()
        if (bigInt != null && (bigInt.compareTo(LONG_MIN) < 0 || bigInt.compareTo(LONG_MAX) > 0)) {
            raiseOverflowException(number, targetClass);
        }
        return number.longValue();
    }

    private static void raiseOverflowException(Number number, Class<?> targetClass) {
        throw new IllegalArgumentException("Could not convert number [" + number + "] of type [" +
            number.getClass().getName() + "] to target class [" + targetClass.getName() + "]: overflow");
    }

我很好奇为什么！

Answer 1

因为没有溢出。

如果你这样做：

Float aFloat = NumberUtils.convertNumberToTargetClass(Double.MAX_VALUE, Float.class);

aFloat 的值将为 Infinity。

查看 API 文档：https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/Float.html

为什么在Spring Boot framework源代码中将"Number"转换为"Float"或"Double"时不检查范围溢出

Why don't check the range overflow when converting "Number" to "Float" or "Double" in Spring Boot framework source code

spring

frameworks

spring-boot