如何利用Java虚拟Unix/Linux的文件路径

/**
* Creates a new File instance by converting the given
* pathname string into an abstract pathname. If the given string is
* the empty string, then the result is the empty abstract pathname.
*
* @param pathname A pathname string
* @throws NullPointerException
* If the pathname argument is null
*/
public File(String pathname) {
//new function
initmaps();

if (pathname == null) {
throw new NullPointerException();
}
//new function
pathname=getVirtualPath(pathname);

this.path = fs.normalize(pathname);
this.prefixLength = fs.prefixLength(this.path);
}

public File(String parent, String child) {
//new function
initmaps();

if (child == null) {
throw new NullPointerException();
}
//new function
child=getVirtualPath(child);
parent=getVirtualPath(parent);

if (parent != null) {
if (parent.equals("")) {

this.path = fs.resolve(fs.getDefaultParent(),
fs.normalize(child));
} else {

this.path = fs.resolve(fs.normalize(parent),
fs.normalize(child));
}
} else {
this.path = fs.normalize(child);
}
this.prefixLength = fs.prefixLength(this.path);
}


public File(File parent, String child) {
//new function
initmaps();
child=getVirtualPath(child);

if (child == null) {
throw new NullPointerException();
}
if (parent != null) {
if (parent.path.equals("")) {
this.path = fs.resolve(fs.getDefaultParent(),
fs.normalize(child));
} else {
String parentpath=getVirtualPath(parent.path); 
this.path = fs.resolve(parent.path,
fs.normalize(child));
}
} else {
this.path = fs.normalize(child);
}
this.prefixLength = fs.prefixLength(this.path);
}