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Add default capacity to EnumTypeAdapter maps #2959

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Merged
eamonnmcmanus merged 3 commits into from
Jan 12, 2026
+16 −3
Merged

Add default capacity to EnumTypeAdapter maps #2959

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Add default capacity to EnumTypeAdapter maps
MukjepScarlet Dec 3, 2025
8b4ab01
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MukjepScarlet Jan 11, 2026
1af3017
inline default load factor
MukjepScarlet Jan 12, 2026
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19 changes: 16 additions & 3 deletions gson/src/main/java/com/google/gson/internal/bind/EnumTypeAdapter.java
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Original file line number Diff line number Diff line change
Expand Up @@ -50,9 +50,16 @@ public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) {
}
};

private final Map<String, T> nameToConstant = new HashMap<>();
private final Map<String, T> stringToConstant = new HashMap<>();
private final Map<T, String> constantToName = new HashMap<>();
/**
* Taken from Java 19 method {@link HashMap.newHashMap}, using default load factor {@code 0.75F}.
*/
private static int calculateHashMapCapacity(int numMappings) {
return (int) Math.ceil(numMappings / 0.75F);
}

private final Map<String, T> nameToConstant;
private final Map<String, T> stringToConstant;
private final Map<T, String> constantToName;

private EnumTypeAdapter(Class<T> classOfT) {
try {
Expand All @@ -71,6 +78,12 @@ private EnumTypeAdapter(Class<T> classOfT) {
// one declared field which is not an enum constant, namely the implicit $VALUES array
fields = Arrays.copyOf(fields, constantCount);

int hashMapCapacity = calculateHashMapCapacity(constantCount);
nameToConstant = new HashMap<>(hashMapCapacity);
stringToConstant = new HashMap<>(hashMapCapacity);
// Don't use `EnumMap` here; that can break when using ProGuard or R8
constantToName = new HashMap<>(hashMapCapacity);

AccessibleObject.setAccessible(fields, true);

for (Field constantField : fields) {
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