add AssetsManager

src/main/java/ghast/AssetsException.java

@@ -0,0 +1,13 @@
+package ghast;
+
+public class AssetsException extends RuntimeException {
+
+	public AssetsException(String message) {
+		super(message);
+	}
+
+	public AssetsException(String message, Throwable cause) {
+		super(message, cause);
+	}
+}
+

src/main/java/ghast/AssetsManager.java

@@ -0,0 +1,42 @@
+package ghast;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+import static java.text.MessageFormat.format;
+
+@SuppressWarnings("unused")
+public final class AssetsManager {
+
+	private AssetsManager() {
+		// this is utility class
+	}
+
+	public static void saveTo(String resourceName, Path targetPath) {
+		URL resourceUrl = AssetsManager.class.getClassLoader().getResource(resourceName);
+		if (resourceUrl == null) {
+			throw new AssetsException(format("Asset \"{0}\" not found", resourceName));
+		}
+
+		try (InputStream inputStream = resourceUrl.openStream();
+			 OutputStream outputStream = Files.newOutputStream(targetPath)) {
+
+			byte[] buffer = new byte[8192];
+			int count;
+			while((count = inputStream.read(buffer)) != -1) {
+				outputStream.write(buffer, 0, count);
+			}
+		} catch (IOException e) {
+			throw new AssetsException(format("Error save asset \"{0}\": {1}", resourceName, e.getMessage()), e);
+		}
+	}
+
+	public static void saveTo(String resourceName, File targetPath) {
+		saveTo(resourceName, targetPath.toPath());
+	}
+}