But it fails with java.util.concurrent.CompletionException: java.lang.Error: Unresolved compilation problems: References to interface static methods are allowed only at source level 1.8 or above Lambda expressions are allowed only at source level 1.8 or above Lambda expressions are allowed only at source level 1.8 or above at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:314) at java.base/java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:319) at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1702) at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.exec(CompletableFuture.java:1692) at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290) at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020) at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656) at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594) at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183) Caused by: java.lang.Error: Unresolved compilation problems: References to interface static methods are allowed only at source level 1.8 or above Lambda expressions are allowed only at source level 1.8 or above Lambda expressions are allowed only at source level 1.8 or above at inc.pulumi.firsttry.ExternalPulumi.getStorageAccountPrimaryKey(ExternalPulumi.java:86) at inc.pulumi.firsttry.ExternalPulumi.callMe(ExternalPulumi.java:76) at myproject.App.lambda$0(App.java:36) at com.pulumi.internal.PulumiInternal.lambda$runAsync$1(PulumiInternal.java:62) at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1700) ... 6 more Any ideas?