Sathish, would you mind elaborating on your use case a bit more, please? That is, I am not able to see where and how you want to leverage `Number#parseNumber(String)` in the `testNumberMemoryUsage()` method. Example: *"I have this test method verifying this behavior of that application. Given a `Number#parseNumber(String)`, I can improve this as follows."*
On Fri, Mar 28, 2025 at 6:31 PM Sathish Kumar Thiyagarajan < sathishkumar.thiyagara...@gmail.com> wrote: > Dear Core-Libs Dev Team, > > *Note:* I have now subscribed to the mailing list and am resending this > message as advised. > > I would like to propose an improvement to the JDK: a *generalized > Number.parseNumber(String) method*. > Motivation > > Java provides multiple number types (byte, short, int, long, etc.), and > developers typically choose them based on memory considerations. Currently, > Java offers String to Number conversions using concrete classes: > > - > > Long.parseLong(String) > - > > Integer.parseInt(String) > - > > Short.parseShort(String), etc. > > While these are useful, Java lacks a *generalized method* that returns > the most memory-efficient Number representation based on the input, like: > > Number.parseNumber(String numberAsText); > > Use Case: JSON Serialization > > This would be particularly useful in cases like *JSON serialization in > REST APIs (Using Jackson <https://github.com/FasterXML/jackson>)*, where > number types are often altered during serialization/deserialization. > Consider the following test case: > > @Test > void testNumberMemoryUsage() throws JsonProcessingException { > ObjectMapper mapper = new ObjectMapper(); > Map<String, Object> numbersObject = Map.of("aShort", (short) 1234, > "aFloat", (float) 1.33); > > final String jsonText = mapper.writeValueAsString(numbersObject); > Map<String, Object> parsedJsonObject = mapper.readValue(jsonText, new > TypeReference<>() {}); > > // Expected: Short.class | Actual: Integer.class > assertEquals(Short.class, parsedJsonObject.get("aShort").getClass()); > > // Expected: Float.class | Actual: Double.class > assertEquals(Float.class, parsedJsonObject.get("aFloat").getClass()); > } > > Reference Implementation > > Here’s a rough implementation to illustrate the idea: > > private static Number parseNumber(final String numberStr) { > try { > if (numberStr.contains(".")) { > double doubleValue = Double.parseDouble(numberStr); > return (doubleValue >= -Float.MAX_VALUE && doubleValue <= > Float.MAX_VALUE) ? > (float) doubleValue : doubleValue; > } else { > long longValue = Long.parseLong(numberStr); > if (longValue >= Byte.MIN_VALUE && longValue <= Byte.MAX_VALUE) { > return (byte) longValue; > } else if (longValue >= Short.MIN_VALUE && longValue <= > Short.MAX_VALUE) { > return (short) longValue; > } else if (longValue >= Integer.MIN_VALUE && longValue <= > Integer.MAX_VALUE) { > return (int) longValue; > } else { > return longValue; > } > } > } catch (NumberFormatException e) { > return parseBigNumber(numberStr); > } > } > > private static Number parseBigNumber(final String numberStr) { > try { > return new BigInteger(numberStr); // Try BigInteger first > } catch (NumberFormatException e) { > // Only create BigDecimal if BigInteger fails > BigDecimal bd = new BigDecimal(numberStr); > try { > // Convert to BigInteger if there's no fraction > return bd.toBigIntegerExact(); > } catch (ArithmeticException ex) { > return bd; // If it's a decimal, return BigDecimal > } > } > } > > Would love to hear your thoughts on this proposal. Appreciate your > feedback and guidance! > > Thanks & Regards, > Sathish Kumar Thiyagarajan >
