Add and throw custom invalid state error

src/main/java/net/lostluma/battery/api/Battery.java

@@ -1,5 +1,6 @@
 package net.lostluma.battery.api;
 
+import net.lostluma.battery.api.exception.InvalidStateError;
 import org.jetbrains.annotations.NotNull;
 
 import java.io.IOException;
@@ -127,7 +128,7 @@ public interface Battery {
      * Refresh battery information in-place.
      *
      * @throws IOException battery information couldn't be refreshed.
-     * @throws RuntimeException the associated manager is not active.
+     * @throws InvalidStateError the associated manager isn't active.
      */
-    void update() throws IOException, RuntimeException;
+    void update() throws IOException, InvalidStateError;
 }

src/main/java/net/lostluma/battery/api/Manager.java

@@ -1,5 +1,6 @@
 package net.lostluma.battery.api;
 
+import net.lostluma.battery.api.exception.InvalidStateError;
 import net.lostluma.battery.api.exception.LibraryLoadError;
 import net.lostluma.battery.impl.ManagerImpl;
 import org.jetbrains.annotations.NotNull;
@@ -32,9 +33,9 @@ public interface Manager extends AutoCloseable {
      *
      * @return the system's current batteries.
      * @throws IOException looking up the batteries failed.
-     * @throws RuntimeException the manager is already closed.
+     * @throws InvalidStateError the manager is already closed.
      */
-    @NotNull Collection<Battery> batteries() throws IOException, RuntimeException;
+    @NotNull Collection<Battery> batteries() throws IOException, InvalidStateError;
 
     /**
      * Close the manager.

src/main/java/net/lostluma/battery/api/exception/InvalidStateError.java

@@ -0,0 +1,14 @@
+package net.lostluma.battery.api.exception;
+
+import org.jetbrains.annotations.ApiStatus;
+
+/**
+ * Error thrown when calling a method on a closed object.
+ */
+// TODO (breaking): Subclass Error instead
+public class InvalidStateError extends RuntimeException {
+    @ApiStatus.Internal
+    public InvalidStateError(String message) {
+        super(message);
+    }
+}

src/main/java/net/lostluma/battery/impl/BatteryImpl.java

@@ -1,5 +1,6 @@
 package net.lostluma.battery.impl;
 
+import net.lostluma.battery.api.exception.InvalidStateError;
 import net.lostluma.battery.api.Battery;
 import net.lostluma.battery.api.State;
 import net.lostluma.battery.api.Technology;
@@ -49,11 +50,11 @@ private BatteryImpl(long ptr, ManagerImpl manager, Technology technology, @Nulla
     }
 
     @Override
-    public void update() throws IOException, RuntimeException {
+    public void update() throws IOException, InvalidStateError {
         if (this.manager.isActive()) {
             this.update0();
         } else {
-            throw new RuntimeException("Attached manager is closed.");
+            throw new InvalidStateError("Attached manager is closed.");
         }
     }
 

src/main/java/net/lostluma/battery/impl/ManagerImpl.java

@@ -2,6 +2,7 @@
 
 import net.lostluma.battery.api.Battery;
 import net.lostluma.battery.api.Manager;
+import net.lostluma.battery.api.exception.InvalidStateError;
 import net.lostluma.battery.api.exception.LibraryLoadError;
 import net.lostluma.battery.impl.util.NativeUtil;
 import org.jetbrains.annotations.ApiStatus;
@@ -41,7 +42,7 @@ boolean isActive() {
     }
 
     @Override
-    public @NotNull Collection<Battery> batteries() throws IOException, RuntimeException {
+    public @NotNull Collection<Battery> batteries() throws IOException, InvalidStateError {
         if (this.isActive()) {
             BatteryImpl[] batteries = this.batteries0();
 
@@ -57,7 +58,7 @@ boolean isActive() {
 
             return Arrays.asList(batteries);
         } else {
-            throw new RuntimeException("Manager can not be used after being closed!");
+            throw new InvalidStateError("Manager can not be used after being closed!");
         }
     }