Windows下Java File对象创建文件夹时的一个"坑"

import java.io.File;
import java.io.IOException;

public class DirCreate {

    public static void main(String[] args) throws IOException {
        // TODO Auto-generated method stub
        String dirStr="D:";
        File dir=new File(dirStr);
        System.out.println("=================1=================");
        System.out.println(dir.getAbsolutePath());
        System.out.println(dir.getCanonicalPath());

        dir=new File(dirStr+File.separator);
        System.out.println("=================2=================");
        System.out.println(dir.getAbsolutePath());
        System.out.println(dir.getCanonicalPath());

        dir=new File(dirStr,"placeholder").getParentFile();
        System.out.println("=================3=================");
        System.out.println(dir.getAbsolutePath());
        System.out.println(dir.getCanonicalPath());
    }
}

output:

==================================
D:\testWorkspace//打印的是eclipse的workspace
D:\testWorkspace
==================================
D:\
D:\
==================================
D:\
D:\

解析：

 String java.io.File.getAbsolutePath()

Returns the absolute pathname string of this abstract pathname. 

If this abstract pathname is already absolute, then the pathname string is simply returned as if by the getPath method. If this abstract pathname is the empty abstract pathname then the pathname string of the current user directory, 
which is named by the system property user.dir, is returned. 
Otherwise this pathname is resolved in a system-dependent way. On UNIX systems, a relative pathname is made absolute by resolving it against the current user directory. On Microsoft Windows systems, a relative pathname is made absolute by resolving it against the current directory of the drive named by the pathname, if any; if not, it is resolved against the current user directory.

Returns:
The absolute pathname string denoting the same file or directory as this abstract pathname
Throws:
SecurityException - If a required system property value cannot be accessed.
See Also:
java.io.File.isAbsolute()