How to get file size in Java

Use the length() method in the File class. From the javadocs:

Returns the length of the file denoted by this abstract pathname. The return value is unspecified if this pathname denotes a directory.

UPDATED Nowadays we should use the Files.size() method:

Path path = Paths.get("/path/to/file");
long size = Files.size(path);

For the second part of the question, straight from File's javadocs:

• getUsableSpace() Returns the number of bytes available to this virtual machine on the partition named by this abstract pathname

• getTotalSpace() Returns the size of the partition named by this abstract pathname

• getFreeSpace() Returns the number of unallocated bytes in the partition named by this abstract path name

Try this:

long length = f.length();