[I] Avoid a slow exception catch in JdkMapAdapterStringMap constructor (logging-log4j2)

[via GitHub]

ppkarwasz opened a new issue, #2238:
URL: https://github.com/apache/logging-log4j2/issues/2238

   ### Discussed in https://github.com/apache/logging-log4j2/discussions/2235
   
   <div type='discussions-op-text'>
   
   <sup>Originally posted by **jdgenerix** January 24, 2024</sup>
   The `org.apache.logging.log4j.core.impl.JdkMapAdapterStringMap` constructor 
is called from `org.apache.logging.log4j.core.impl.ThreadContextDataInjector` 
with an UnmodiableMap (`copy`) and the constructor is trying to modify and 
catch an exception to detect if this is an immutable Map.
   This code is triggered a lot of time and could be more efficient.
   Adding a package protected constructor which take the immutable boolean flag 
as an argument and using it from `ThreadContextDataInjector` would avoid this 
slow try catch.
   
   ```java
           @Override
           public ReadOnlyStringMap rawContextData() {
               final ReadOnlyThreadContextMap map = 
ThreadContext.getThreadContextMap();
               if (map instanceof ReadOnlyStringMap) {
                   return (ReadOnlyStringMap) map;
               }
               // note: default ThreadContextMap is null
               final Map<String, String> copy = 
ThreadContext.getImmutableContext();
               return copy.isEmpty() ? 
ContextDataFactory.emptyFrozenContextData() : new JdkMapAdapterStringMap(copy);
           }
   
   
           public JdkMapAdapterStringMap(final Map<String, String> map) {
                this.map = Objects.requireNonNull(map, "map");
                try {
                        map.replace(Strings.EMPTY, Strings.EMPTY, 
Strings.EMPTY);
                } catch (final UnsupportedOperationException ignored) {
                        immutable = true;
                }
        }
   ```</div>


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