如何在 Java 中的递归方法中获取 Sum

Question

I am trying to get a total of n in the following recursive method. But the problem is it prints n in each recursion call.

    public void recur2(Folder folder) {
    
    int n = 0;
    
    if (folder.getSubfolders() != null) {
        
        n += folder.getSubfolders().size();
        
        Set<Folder> folders = folder.getSubfolders();
        
        for(Folder fldr: folders) {
            recur2(fldr);
        }
    }
    System.out.println(n);
}

The output is something like this:

0 0 0 3 0 1 0 0 0 0 4 0 0 0 0 4 4 1

What I'm looking for is the total of the above numbers which is 17.

So, what would be the solution to this issue?

I looked at the same topics here and it looks like there isn't any useful answer to this problem. Please help me with the complete method.

Answer 1

public long getTotalSubfolders(Folder folder) {
    if(folder == null)
        return 0;
    if(folder.getSubfolders() == null)
        return 0;
    
    long n = folder.getSubfolders().size();
    
    for(Folder subFolder : folder.getSubfolders())
        n += getSubfolders(subFolder);
    
    return n;
}