feat: Performance enhancements

src/main/java/dev/openfeature/sdk/FlagEvaluationDetails.java

@@ -1,6 +1,5 @@
 package dev.openfeature.sdk;
 
-import java.util.Optional;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
@@ -26,7 +25,7 @@ public class FlagEvaluationDetails<T> implements BaseEvaluation<T> {
     private String errorMessage;
 
     @Builder.Default
-    private ImmutableMetadata flagMetadata = ImmutableMetadata.builder().build();
+    private ImmutableMetadata flagMetadata = ImmutableMetadata.EMPTY;
 
     /**
      * Generate detail payload from the provider response.
@@ -37,15 +36,18 @@ public class FlagEvaluationDetails<T> implements BaseEvaluation<T> {
      * @return detail payload
      */
     public static <T> FlagEvaluationDetails<T> from(ProviderEvaluation<T> providerEval, String flagKey) {
-        return FlagEvaluationDetails.<T>builder()
-                .flagKey(flagKey)
-                .value(providerEval.getValue())
-                .variant(providerEval.getVariant())
-                .reason(providerEval.getReason())
-                .errorMessage(providerEval.getErrorMessage())
-                .errorCode(providerEval.getErrorCode())
-                .flagMetadata(Optional.ofNullable(providerEval.getFlagMetadata())
-                        .orElse(ImmutableMetadata.builder().build()))
-                .build();
+        var flagMetadata = providerEval.getFlagMetadata();
+        if (flagMetadata == null) {
+            flagMetadata = ImmutableMetadata.EMPTY;
+        }
+
+        return new FlagEvaluationDetails<>(
+                flagKey,
+                providerEval.getValue(),
+                providerEval.getVariant(),
+                providerEval.getReason(),
+                providerEval.getErrorCode(),
+                providerEval.getErrorMessage(),
+                flagMetadata);
     }
 }

src/main/java/dev/openfeature/sdk/FlagEvaluationOptions.java

@@ -9,7 +9,11 @@
 @SuppressWarnings("checkstyle:MissingJavadocType")
 @lombok.Value
 @Builder
 public class FlagEvaluationOptions {
+
+    public static final FlagEvaluationOptions EMPTY =
+            FlagEvaluationOptions.builder().build();
+
     @Singular
     List<Hook> hooks;
 

src/main/java/dev/openfeature/sdk/HashMapUtils.java

@@ -0,0 +1,11 @@
+package dev.openfeature.sdk;
+
+import java.util.HashMap;
+
+class HashMapUtils {
+    private HashMapUtils() {}
+
+    static <K, V> HashMap<K, V> forEntries(int expectedEntries) {
+        return new HashMap<>((int) Math.ceil(expectedEntries / .75));
+    }
+}

src/main/java/dev/openfeature/sdk/ImmutableContext.java

@@ -1,6 +1,7 @@
 package dev.openfeature.sdk;
 
 import dev.openfeature.sdk.internal.ExcludeFromGeneratedCoverageReport;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.function.Function;
@@ -20,7 +21,7 @@
 @SuppressWarnings("PMD.BeanMembersShouldSerialize")
 public final class ImmutableContext implements EvaluationContext {
 
-    public static final ImmutableContext EMPTY = new ImmutableContext();
+    public static final ImmutableContext EMPTY = new ImmutableContext(Collections.emptyMap());
 
     @Delegate(excludes = DelegateExclusions.class)
     private final ImmutableStructure structure;
@@ -58,7 +59,7 @@ public ImmutableContext(Map<String, Value> attributes) {
      * @param attributes   evaluation context attributes
      */
     public ImmutableContext(String targetingKey, Map<String, Value> attributes) {
-        if (targetingKey != null && !targetingKey.trim().isEmpty()) {
+        if (targetingKey != null && !targetingKey.isBlank()) {
             this.structure = new ImmutableStructure(targetingKey, attributes);
         } else {
             this.structure = new ImmutableStructure(attributes);

src/main/java/dev/openfeature/sdk/ImmutableStructure.java

@@ -4,7 +4,6 @@
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Map.Entry;
-import java.util.Optional;
 import java.util.Set;
 import lombok.EqualsAndHashCode;
 import lombok.ToString;
@@ -69,15 +68,21 @@ private static Map<String, Value> copyAttributes(Map<String, Value> in) {
     }
 
     private static Map<String, Value> copyAttributes(Map<String, Value> in, String targetingKey) {
-        Map<String, Value> copy = new HashMap<>();
+        Map<String, Value> copy;
         if (in != null) {
+            var numMappings = in.size();
+            if (targetingKey != null) {
+                numMappings++;
+            }
+            copy = HashMapUtils.forEntries(numMappings);
             for (Entry<String, Value> entry : in.entrySet()) {
-                copy.put(
-                        entry.getKey(),
-                        Optional.ofNullable(entry.getValue())
-                                .map((Value val) -> val.clone())
-                                .orElse(null));
+                var key = entry.getKey();
+                var value = entry.getValue();
+                Value cloned = value == null ? null : value.clone();
+                copy.put(key, cloned);
             }
+        } else {
+            copy = new HashMap<>(targetingKey == null ? 0 : 1);
         }
         if (targetingKey != null) {
             copy.put(EvaluationContext.TARGETING_KEY, new Value(targetingKey));

src/main/java/dev/openfeature/sdk/OpenFeatureClient.java

@@ -163,8 +163,13 @@ private <T> FlagEvaluationDetails<T> evaluateFlag(
         FlagEvaluationDetails<T> details = null;
         HookSupportData hookSupportData = new HookSupportData();
 
-        var flagOptions = ObjectUtils.defaultIfNull(
-                options, () -> FlagEvaluationOptions.builder().build());
+        FlagEvaluationOptions flagOptions;
+        if (options == null) {
+            flagOptions = FlagEvaluationOptions.EMPTY;
+        } else {
+            flagOptions = options;
+        }
+
         hookSupportData.hints = Collections.unmodifiableMap(flagOptions.getHookHints());
         var context = new LayeredEvaluationContext(
                 openfeatureApi.getEvaluationContext(),
@@ -323,8 +328,7 @@ public FlagEvaluationDetails<Boolean> getBooleanDetails(String key, Boolean defa
 
     @Override
     public FlagEvaluationDetails<Boolean> getBooleanDetails(String key, Boolean defaultValue, EvaluationContext ctx) {
-        return getBooleanDetails(
-                key, defaultValue, ctx, FlagEvaluationOptions.builder().build());
+        return getBooleanDetails(key, defaultValue, ctx, FlagEvaluationOptions.EMPTY);
     }
 
     @Override
@@ -356,8 +360,7 @@ public FlagEvaluationDetails<String> getStringDetails(String key, String default
 
     @Override
     public FlagEvaluationDetails<String> getStringDetails(String key, String defaultValue, EvaluationContext ctx) {
-        return getStringDetails(
-                key, defaultValue, ctx, FlagEvaluationOptions.builder().build());
+        return getStringDetails(key, defaultValue, ctx, FlagEvaluationOptions.EMPTY);
     }
 
     @Override
@@ -389,8 +392,7 @@ public FlagEvaluationDetails<Integer> getIntegerDetails(String key, Integer defa
 
     @Override
     public FlagEvaluationDetails<Integer> getIntegerDetails(String key, Integer defaultValue, EvaluationContext ctx) {
-        return getIntegerDetails(
-                key, defaultValue, ctx, FlagEvaluationOptions.builder().build());
+        return getIntegerDetails(key, defaultValue, ctx, FlagEvaluationOptions.EMPTY);
     }
 
     @Override
@@ -454,8 +456,7 @@ public FlagEvaluationDetails<Value> getObjectDetails(String key, Value defaultVa
 
     @Override
     public FlagEvaluationDetails<Value> getObjectDetails(String key, Value defaultValue, EvaluationContext ctx) {
-        return getObjectDetails(
-                key, defaultValue, ctx, FlagEvaluationOptions.builder().build());
+        return getObjectDetails(key, defaultValue, ctx, FlagEvaluationOptions.EMPTY);
     }
 
     @Override
@@ -466,7 +467,7 @@ public FlagEvaluationDetails<Value> getObjectDetails(
 
     @Override
     public ClientMetadata getMetadata() {
-        return () -> domain;
+        return this::getDomain;
     }
 
     /**