Trim thread local string builder if large
Motivation: A previous change allocated a new thread local string builder if it was getting too large. This is a good change, these string builders can accidentally get too large and then never shrunk and that is sort of a memory leak. However, the change allocates an entirely new string builder which is more allocations than necessary. Instead, we can trim the string builder if its too large, this only allocates an extra backing array instead of a whole new object. Modifications: If the string builder is above a threshold, we trim the string builder and then ensure its capacity is reasonable to we do not allocate too much as we start using the string builder. Result: The thread local string builder do not serve as a memory yet we do not allocate too many new objects.
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@ -35,7 +35,6 @@ import java.util.WeakHashMap;
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*/
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public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap {
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private static final int STRING_BUILDER_MAX_CAPACITY = 1024 << 6;
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private static final int DEFAULT_ARRAY_LIST_INITIAL_CAPACITY = 8;
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public static final Object UNSET = new Object();
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@ -164,13 +163,17 @@ public final class InternalThreadLocalMap extends UnpaddedInternalThreadLocalMap
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}
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public StringBuilder stringBuilder() {
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StringBuilder builder = stringBuilder;
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if (builder == null || builder.capacity() > STRING_BUILDER_MAX_CAPACITY) {
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stringBuilder = builder = new StringBuilder(512);
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final int stringBuilderCapacity = 1024;
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if (stringBuilder == null) {
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stringBuilder = new StringBuilder(stringBuilderCapacity);
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} else {
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builder.setLength(0);
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if (stringBuilder.capacity() > stringBuilderCapacity) {
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stringBuilder.setLength(stringBuilderCapacity);
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stringBuilder.trimToSize();
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}
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return builder;
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stringBuilder.setLength(0);
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}
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return stringBuilder;
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}
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public Map<Charset, CharsetEncoder> charsetEncoderCache() {
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