diff --git a/paper-server/src/main/java/org/bukkit/craftbukkit/util/Waitable.java b/paper-server/src/main/java/org/bukkit/craftbukkit/util/Waitable.java new file mode 100644 index 0000000000..5cd1154348 --- /dev/null +++ b/paper-server/src/main/java/org/bukkit/craftbukkit/util/Waitable.java @@ -0,0 +1,46 @@ +package org.bukkit.craftbukkit.util; + +import java.util.concurrent.ExecutionException; + + +public abstract class Waitable implements Runnable { + private enum Status { + WAITING, + RUNNING, + FINISHED, + } + Throwable t = null; + T value = null; + Status status = Status.WAITING; + + public final void run() { + synchronized (this) { + if (status != Status.WAITING) { + throw new IllegalStateException("Invalid state " + status); + } + status = Status.RUNNING; + } + try { + value = evaluate(); + } catch (Throwable t) { + this.t = t; + } finally { + synchronized (this) { + status = Status.FINISHED; + this.notifyAll(); + } + } + } + + protected abstract T evaluate(); + + public synchronized T get() throws InterruptedException, ExecutionException { + while (status != Status.FINISHED) { + this.wait(); + } + if (t != null) { + throw new ExecutionException(t); + } + return value; + } +}