Here are results for a few sample runs using the a4 test data

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java test.DiskUsage a4

5 FILE /Users/bernhard/Desktop/204/a4/d1/inD1
11 FILE /Users/bernhard/Desktop/204/a4/d0/inD0
31 FILE /Users/bernhard/Desktop/204/a4/d0/d2/inD2
399958 FILE /Users/bernhard/Desktop/204/a4/d1/zzz
399963 DIR  /Users/bernhard/Desktop/204/a4/d1
400001 FILE /Users/bernhard/Desktop/204/a4/d0/d2/yyy
400004 FILE /Users/bernhard/Desktop/204/a4/xxx~
400004 FILE /Users/bernhard/Desktop/204/a4/zzz
400018 FILE /Users/bernhard/Desktop/204/a4/xxx
400032 DIR  /Users/bernhard/Desktop/204/a4/d0/d2
400043 DIR  /Users/bernhard/Desktop/204/a4/d0
2000032 DIR  /Users/bernhard/Desktop/204/a4

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java test.DiskUsage -s a4

2000032 DIR  /Users/bernhard/Desktop/204/a4

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java test.DiskUsage -s `pwd`

4191636 DIR  /Users/bernhard/Desktop/204

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java test.DiskUsage -s a4/d0

400043 DIR  /Users/bernhard/Desktop/204/a4/d0

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java test.DiskUsage  a4/d0

11 FILE /Users/bernhard/Desktop/204/a4/d0/inD0
31 FILE /Users/bernhard/Desktop/204/a4/d0/d2/inD2
400001 FILE /Users/bernhard/Desktop/204/a4/d0/d2/yyy
400032 DIR  /Users/bernhard/Desktop/204/a4/d0/d2
400043 DIR  /Users/bernhard/Desktop/204/a4/d0

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Just in case, here is a full listing of the unpacked tar file contents:

ls -lR a4
total 2360
drwxr-xr-x   4 bernhard  bernhard     136 Sep 12 23:11 d0
drwxr-xr-x   4 bernhard  bernhard     136 Sep 12 23:11 d1
-rw-r--r--   1 bernhard  bernhard  400018 Sep 12 23:10 xxx
-rw-r--r--   2 bernhard  bernhard  400004 Sep 12 23:06 xxx~
lrwxr-xr-x   1 bernhard  bernhard       3 Sep 12 23:07 yyy -> xxx
-rw-r--r--   2 bernhard  bernhard  400004 Sep 12 23:06 zzz

a4/d0:
total 8
drwxr-xr-x   4 bernhard  bernhard  136 Sep 12 23:11 d2
-rw-r--r--   1 bernhard  bernhard   11 Sep 12 23:11 inD0

a4/d0/d2:
total 792
-rw-r--r--   1 bernhard  bernhard      31 Sep 12 23:12 inD2
-rw-r--r--   1 bernhard  bernhard  400001 Sep 12 23:08 yyy

a4/d1:
total 792
-rw-r--r--   1 bernhard  bernhard       5 Sep 12 23:11 inD1
-rw-r--r--   1 bernhard  bernhard  399958 Sep 12 23:09 zzz