done

src/Enemy.java

@@ -0,0 +1,61 @@
+public abstract class Enemy implements Character {
+
+    private final String name;
+    private int hitPoints;
+
+    protected Enemy(String name, int hitPoints) {
+        if (name == null || name.isBlank()) {
+            throw new IllegalArgumentException(
+                    "Name must not be blank"
+            );
+        }
+
+        if (hitPoints <= 0) {
+            throw new IllegalArgumentException(
+                    "Hit points must be positive"
+            );
+        }
+
+        this.name = name;
+        this.hitPoints = hitPoints;
+    }
+
+    @Override
+    public final String getName() {
+        return name;
+    }
+
+    @Override
+    public final int getHitPoints() {
+        return hitPoints;
+    }
+
+    @Override
+    public final boolean isDefeated() {
+        return hitPoints == 0;
+    }
+
+    protected final void takeDamage(int damage) {
+        if (damage < 0) {
+            throw new IllegalArgumentException(
+                    "Damage must not be negative"
+            );
+        }
+
+        hitPoints = Math.max(
+                0,
+                hitPoints - damage
+        );
+    }
+
+    @Override
+    public final String toString() {
+        return "%s{name='%s', hitPoints=%d, defeated=%s}"
+                .formatted(
+                        getClass().getSimpleName(),
+                        name,
+                        hitPoints,
+                        isDefeated()
+                );
+    }
+}