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Upstream Bug: JsonNumber.of(double) hardcodes decimalOffset causing toLong to fail #118
Description
Summary
The JsonNumber.of(double) factory method has a bug where it hardcodes decimalOffset=0 and exponentOffset=0 when creating the JsonNumberImpl. This causes toLong() to fail for integral doubles like 123.0.
Root Cause
In JsonNumber.java line 117:
static JsonNumber of(double num) {
if (!Double.isFinite(num)) {
throw new IllegalArgumentException("Not a valid JSON number");
}
var str = Double.toString(num);
return new JsonNumberImpl(str.toCharArray(), 0, str.length(), 0, 0);
// ^^^^^ BUG: hardcoded offsets
}For Double.toString(123.0) which returns "123.0":
decimalOffsetshould be3(position of.) but is passed as0- This causes
initNumLong()inJsonNumberImplto misparse the number
Reproduction
var jn = JsonNumber.of(123.0);
jn.toString(); // "123.0" - OK
jn.toDouble(); // 123.0 - OK
jn.toLong(); // THROWS: "123.0 cannot be represented as a long"
// EXPECTED: 123L (per API docs, "123.0" should be convertible)Comparison with Json.parse()
var parsed = Json.parse("123.0");
parsed.toLong(); // 123L - WORKS correctlyThe difference is that Json.parse() correctly computes the decimalOffset during parsing.
Suggested Fix
Option 1 - Reuse JsonNumber.of(String) which delegates to parser:
static JsonNumber of(double num) {
if (!Double.isFinite(num)) {
throw new IllegalArgumentException("Not a valid JSON number");
}
return JsonNumber.of(Double.toString(num));
}Option 2 - Compute correct offsets:
static JsonNumber of(double num) {
if (!Double.isFinite(num)) {
throw new IllegalArgumentException("Not a valid JSON number");
}
var str = Double.toString(num);
var chars = str.toCharArray();
int dec = str.indexOf('.');
int exp = str.indexOf('e');
if (exp == -1) exp = str.indexOf('E');
return new JsonNumberImpl(chars, 0, chars.length,
dec == -1 ? -1 : dec,
exp == -1 ? -1 : exp);
}This is an Upstream Bug
This bug exists in OpenJDK jdk-sandbox json branch at commit 91a479d. The upstream tests in TestJsonNumber.java do not cover this case - they test of(double).toDouble() but never of(double).toLong() for integral doubles.
Affected Versions
- jdk-sandbox json branch (upstream)
- java.util.json.Java21 backport 0.1.9 (this repo, synced from upstream)
Activity
simbo1905 commentedon Jan 26, 2026
Update: Upstream Bug Reporting
This is an upstream bug in OpenJDK jdk-sandbox. Per OpenJDK process, bugs should be reported via the core-libs-dev mailing list, not via GitHub issues on jdk-sandbox.
Local Workaround Applied: We've applied a local fix in this backport (delegating
of(double)toof(String)) until upstream addresses this. The fix is documented in README.md under "Upstream Bug Fixes".If anyone wishes to report this upstream:
JsonNumber.of(double)methodIssue #118 fix upstream bug in JsonNumber.of(double) hardcoding offsets
Issue #118 bump expected test count from 507 to 511
simbo1905 commentedon May 19, 2026
Fixed
This bug has been fixed in the backport.
JsonNumber.of(double)now delegates toJsonNumber.of(String)which usesJson.parse()to correctly compute thedecimalOffsetandexponentOffset:Verified:
JsonNumber.of(123.0).toLong()now correctly returns123L. All 27 tests pass.This fix was included in the sync to upstream commit
c1a4f80(release2026.02.05). The upstream bug remains unfixed in jdk-sandbox.Issue #145 port upstream tests, verify #118 closed, bump frontier docs