wang-jiahua opened a new issue, #10511:
URL: https://github.com/apache/rocketmq/issues/10511
### Before Creating the Enhancement Request
- [x] I have confirmed that this should be classified as an enhancement
rather than a bug/feature.
### Summary
`LanguageCode.valueOf(byte)` and `SerializeType.valueOf(byte)` currently
call `values()` in a loop on every invocation. Since JDK requires
`Enum.values()` to return a fresh array each time (defensive copy), this
allocates a new array per call. Replace with a static `BY_CODE[]` array for
O(1) lookup with zero allocation.
### Motivation
JFR `settings=profile` shows these `valueOf(byte)` methods are called on
every RPC decode path. `values()` creates a new array on every call — a per-RPC
allocation that is completely unnecessary since the enum constants are fixed at
class load time.
### Describe the Solution You'd Like
```java
// LanguageCode.java
private static final LanguageCode[] BY_CODE;
static {
LanguageCode[] all = values();
int max = 0;
for (LanguageCode lc : all) {
max = Math.max(max, lc.code & 0xFF);
}
BY_CODE = new LanguageCode[max + 1];
for (LanguageCode lc : all) {
BY_CODE[lc.code & 0xFF] = lc;
}
}
public static LanguageCode valueOf(byte code) {
int idx = code & 0xFF;
return idx < BY_CODE.length ? BY_CODE[idx] : null;
}
```
Same pattern for `SerializeType` (which only has 2 values: JSON=0,
ROCKETMQ=1).
### Describe Alternatives You've Considered
- **HashMap<Byte, LanguageCode>**: Adds boxing overhead (`Byte.valueOf`) and
more memory than a simple array. Array lookup is simpler and faster.
- **Switch statement**: Not applicable since the lookup key is a `byte`
parameter, not a compile-time constant.
### Additional Context
This is the same pattern used in PR #10469 for
`MessageVersion.valueOfMagicCode()` (merged).
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