feat : java-sdk main implementation

sdk/java-sdk/src/main/java/org/lightswitch/sdk/model/FeatureFlag.java

@@ -0,0 +1,56 @@
+package org.lightswitch.sdk.model;
+
+import org.lightswitch.sdk.user.LightSwitchUser;
+
+import java.util.Collections;
+import java.util.Map;
+
+public class FeatureFlag {
+
+    private final String key;
+    private final Object defaultValue;
+    private final Map<Map<String, String>, Object> filters; // filtering rules
+
+    public FeatureFlag(String key, Object defaultValue, Map<Map<String, String>, Object> filters) {
+        this.key = key;
+        this.defaultValue = defaultValue;
+        this.filters = filters != null ? filters : Collections.emptyMap();
+    }
+
+    public String getKey() {
+        return key;
+    }
+
+    public Object getDefaultValue() {
+        return defaultValue;
+    }
+
+    public Map<Map<String, String>, Object> getConditions() {
+        return Collections.unmodifiableMap(filters);
+    }
+
+    /**
+     * Find and return appropriate flag values based on user properties
+     */
+    public Object evaluate(LightSwitchUser user) {
+        for (Map.Entry<Map<String, String>, Object> entry : filters.entrySet()) {
+            Map<String, String> conditions = entry.getKey();
+            boolean match = conditions.entrySet().stream()
+                    .allMatch(cond -> user.getAttributes().getOrDefault(cond.getKey(), "").equals(cond.getValue()));
+
+            if (match) {
+                return entry.getValue();
+            }
+        }
+        return defaultValue;
+    }
+
+    @Override
+    public String toString() {
+        return "FeatureFlag{" +
+                "key='" + key + '\'' +
+                ", defaultValue=" + defaultValue +
+                ", filters=" + filters +
+                '}';
+    }
+}