从相对文件名路径获取绝对文件名路径

import java.io.File;


public class Main {
/*
时   代    Java - nowjava.com 提 供
*/

  public void m() {

    File file = new File("filename.txt");

    file = file.getAbsoluteFile(); // c:\temp\filename.txt


    file = new File("dir" + File.separatorChar + "filename.txt");

    file = file.getAbsoluteFile(); // c:\temp\dir\filename.txt


    file = new File(".." + File.separatorChar + "filename.txt");

    file = file.ge