separated filename shortening layer from metadata hiding layer

main/commons/src/main/java/org/cryptomator/common/LazyInitializer.java

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+package org.cryptomator.common;
+
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.function.Supplier;
+
+public final class LazyInitializer {
+
+	private LazyInitializer() {
+	}
+
+	/**
+	 * Threadsafe lazy initialization pattern as proposed on http://stackoverflow.com/a/30247202/4014509
+	 * 
+	 * @param <T> Type of the value
+	 * @param reference A reference to a maybe not yet initialized value.
+	 * @param factory A factory providing a value for the reference, if it doesn't exist yet. The factory may be invoked multiple times, but only one result will survive.
+	 * @return The initialized value
+	 */
+	public static <T> T initializeLazily(AtomicReference<T> reference, Supplier<T> factory) {
+		final T existingInstance = reference.get();
+		if (existingInstance != null) {
+			return existingInstance;
+		} else {
+			final T newInstance = factory.get();
+			if (reference.compareAndSet(null, newInstance)) {
+				return newInstance;
+			} else {
+				return reference.get();
+			}
+		}
+	}
+
+}