ffdb-005: add synchronized factory for DB

src/main/java/com/sahilbondre/firefly/FireflyDB.java

@@ -1,5 +1,22 @@
 package com.sahilbondre.firefly;
 
+import java.util.HashMap;
+import java.util.Map;
+
 public class FireflyDB {
+    private static final Map<String, FireflyDB> instances = new HashMap<>();
+    private final String folderPath;
+
+    private FireflyDB(String folderPath) {
+        this.folderPath = folderPath;
+    }
+
+    public static synchronized FireflyDB getInstance(String folderPath) {
+        instances.computeIfAbsent(folderPath, FireflyDB::new);
+        return instances.get(folderPath);
+    }
 
+    public String getFolderPath() {
+        return folderPath;
+    }
 }

src/test/java/com/sahilbondre/firefly/FireflyDBTest.java

@@ -0,0 +1,53 @@
+package com.sahilbondre.firefly;
+
+import org.junit.jupiter.api.Test;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Modifier;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class FireflyDBTest {
+
+    private static final String FOLDER_A = "/path/to/folderA";
+    private static final String FOLDER_B = "/path/to/folderB";
+
+    @Test
+    void givenSameFolder_whenGetInstance_thenSameObjectReferenced() {
+        // Given
+        // Two instances with the same folder should reference the same object
+
+        // When
+        FireflyDB dbA1 = FireflyDB.getInstance(FOLDER_A);
+        FireflyDB dbA2 = FireflyDB.getInstance(FOLDER_A);
+
+        // Then
+        assertSame(dbA1, dbA2);
+        assertEquals(FOLDER_A, dbA1.getFolderPath());
+        assertEquals(FOLDER_A, dbA1.getFolderPath());
+    }
+
+    @Test
+    void givenDifferentFolders_whenGetInstance_thenDifferentObjectsReferenced() {
+        // Given
+        // Two instances with different folders should reference different objects
+
+        // When
+        FireflyDB dbA = FireflyDB.getInstance(FOLDER_A);
+        FireflyDB dbB = FireflyDB.getInstance(FOLDER_B);
+
+        // Then
+        assertNotSame(dbA, dbB);
+        assertEquals(FOLDER_A, dbA.getFolderPath());
+        assertEquals(FOLDER_B, dbB.getFolderPath());
+    }
+
+    @Test
+    void givenGetInstanceMethod_whenCheckSynchronizedModifier_thenTrue() throws NoSuchMethodException {
+        // Given
+        Method getInstanceMethod = FireflyDB.class.getDeclaredMethod("getInstance", String.class);
+
+        // When/Then
+        assertTrue(Modifier.isSynchronized(getInstanceMethod.getModifiers()));
+    }
+}