I have a structure similar to the code block below. Somehow I get nullpointerException in CompletableFuture.allOf method:
What could be the problem here?
Thanks..

List<CompletableFuture<String>> completableFutures = new ArrayList<>();

for(Classx list : request.getlist()) {
    switch (list.getCases()) {
        case 1:
            completableFutures.add(asyncProcess(list));
            break;
        case 2:
            completableFutures.add(asyncProcess2(list));
            break;
    }
}
CompletableFuture<Void> allFutures = CompletableFuture.allOf(completableFutures.toArray(new CompletableFuture[0]));


@Async
public CompletableFuture<String> asyncProcess(Classx list) {
    try{
        //..some codes
    } catch(Exception e){
        //..some codes
    }
    return CompletableFuture.completedFuture(x.getX());
}


@Async
public CompletableFuture<String> asyncProcess2(Classx list) {
    try{
        //..some codes
    } catch(Exception e){
        //..some codes
    }
    return CompletableFuture.completedFuture(x.getX());
}

error message is :

java.lang.NullPointerException
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1306)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1305)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.andTree(CompletableFuture.java:1303)
at java.util.concurrent.CompletableFuture.allOf(CompletableFuture.java:2225)

When I change the code as follows, it throws the same error.

CompletableFuture allFutures = CompletableFuture.allOf(completableFutures.toArray(new CompletableFuture[completableFuture.size()]));