Determine if a directory contains a file

I have java.io.File objects A and B, where A represents a directory and B represents a file. B can be an absolute path or a relative path that is 0 or more levels below A. what's the most effi开发者_如何学JAVAcient way to determine if B is contained by A?

For example,

A is C:\Users\bill\Desktop\abc\xyz123 and B is C:\Users\bob\Documents\inc\data.inc

or

A is C:\Users\bill\Desktop\abc\xyz123 and B is C:\Users\bob\Documents\x1\y1\inc\data.inc

or

A is C:\Users\bill\Desktop\abc\xyz123 and B is ..\..\..\Documents\inc\data.inc

You can check to see if A is the parent of B by doing

A.equals(B.getParentFile())

Edit: If you want to check if B is one or more levels below A, just keep getting the ParentFile until it's A or null

File C = B.getParentFile();

while(C != null) {
    if(A.equals(C))
        return true;

    C = C.getParentFile();
}

return false;

getParentFile(), which returns the parent directory, and getCanonicalFile() can be of use. Like so:

File bDir = b.getParentFile();
boolean same = bDir.equals(a) || bDir.getCanonicalFile().equals(a.getCanonicalFile());

Paths can be tricky. If you're lucky the just getParent() is all that's necessary. Using getCanonicalFile() should cover the more complicated cases.

Use the class FileUtils:

public static boolean directoryContains(File directory,
                                        File child)
                                 throws IOException

Determines whether the parent directory contains the child element (a file or directory).