1 files changed, 42 insertions, 0 deletions

diff --git a/src/main/java/zajc/gogarchiver/util/LazyValue.java b/src/main/java/zajc/gogarchiver/util/LazyValue.java
new file mode 100644
index 0000000..118193f
--- /dev/null
+++ b/src/main/java/zajc/gogarchiver/util/LazyValue.java
@@ -0,0 +1,42 @@
+//SPDX-License-Identifier: GPL-3.0
+/*
+ * gogarchiver-ng, an archival tool for GOG.com
+ * Copyright (C) 2024 Marko Zajc
+ *
+ * This program is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with this
+ * program. If not, see <https://www.gnu.org/licenses/>.
+ */
+package zajc.gogarchiver.util;
+
+import java.util.function.Supplier;
+
+import javax.annotation.*;
+
+public class LazyValue<T> {
+
+        @Nullable private volatile T value;
+
+        public T get(@Nonnull Supplier<T> generator) {
+                if (this.value != null)
+                        return this.value;
+                synchronized (this) {
+                        if (this.value != null) // double checked locking
+                                return this.value;
+                        else
+                                return this.value = generator.get();
+                }
+        }
+
+        public synchronized void unset() {
+                this.value = null;
+        }
+
+}