NioFileNullCheck.java

package os;

import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;

public class FileNullCheck
{
    public static void main(String[] args) throws Exception
    {
        File tmp = new File("a.txt");
        try
        {
            tmp.createNewFile();
        }
        catch (IOException e)
        {
            e.printStackTrace();
            return;
        }
        
        String a = "a.txt";
        testExists("a.txt", a);
        
        String anull = new String(new byte[] { 'a', '.', 't', 'x', 't', 0x00 }, "UTF-8");
        testExists("a.txt (null)", anull);

        String anullx = new String(new byte[] { 'a', '.', 't', 'x', 't', 0x00, 'x' }, "UTF-8");
        testExists("a.txt (nullx)", anullx);
    }

    private static void testExists(String label, String filename) throws IOException
    {
        File file = new File(filename);
        File canonical = file.getCanonicalFile();
        boolean normalizedName = filename.length() != file.getCanonicalFile().getName().length();
        boolean canonName = file.getName().equals(canonical.getName());
        System.out.printf("%s exists: %b%n", label, file.exists());
        System.out.printf("  filename.length = %d%n", filename.length());
        System.out.printf("  normalized changed filename length = %b%n", normalizedName);
        System.out.printf("  canonName = %b%n",canonName);
        
        Path path = Paths.get(file.toURI());
        boolean symlink = Files.isSymbolicLink(path);
        System.out.printf("  nio issymlink = %b%n",symlink);
    }
}