public <U> CompletableFuture<U> supplyAsync(Supplier<U> supplier) {
    return CompletableFuture.supplyAsync(supplier, executor);
  }
Returns a new CompletableFuture that is asynchronously completed by a task running in the
dedicated executor with the value obtained by calling the given Supplier.

@param supplier a function returning the value to be used to complete the returned
       CompletableFuture
@param <U> the function's return type
@return the new CompletableFuture
geode-junit/src/main/java/org/apache/geode/test/junit/rules/ExecutorServiceRule.java