@FunctionalInterface
public interface FileFilter {
    /**
     * Tests whether or not the specified abstract pathname should be
     * included in a pathname list.
     *
     * @param  pathname  The abstract pathname to be tested
     * @return  <code>true</code> if and only if <code>pathname</code>
     *          should be included
     */
    boolean accept(File pathname);
}

@FunctionalInterface
public interface FilenameFilter {
    /**
     * Tests if a specified file should be included in a file list.
     *
     * @param   dir    the directory in which the file was found.
     * @param   name   the name of the file.
     * @return  <code>true</code> if and only if the name should be
     * included in the file list; <code>false</code> otherwise.
     */
    boolean accept(File dir, String name);
}

 @Test
    public void DireOperTest(){
       //是一个目录
        File file=new File("E:"+File.separator+"ideaWork"+File.separator+"Java2"+File.separator+"fileSrc");
        //只展示一级的
       String [] fileNames= file.list();
       for(String s:fileNames){
           System.out.println("文件名称:"+s);
       }
       System.out.println("***********************************");
       File[] files=file.listFiles();
       for(File f:files){
           System.out.println("文件名称:"+f.getName());
       }
       System.out.println("***********过滤操作*************");
       File[] filterFiles=file.listFiles(new FilenameFilter() {
           @Override
           public boolean accept(File dir, String name) {
              //第一个指目录文件， 第二个文件的名称。
               System.out.println("文件:"+dir.getAbsolutePath());
               System.out.println("name:"+name);
               //如果名称中包括 . 就返回 
               if(name.indexOf(".")>=0){
                   return true;
               }
               return false;
           }
       });
        System.out.println("最后过滤得到的信息1");
       for(File f:filterFiles){
           System.out.println("过滤后的文件名称:"+f.getName());
       }
        System.out.println("***********又一次过滤*************");
        File[] filter2Files=file.listFiles(new FileFilter() {
            @Override
            public boolean accept(File pathname) {
                //指的是下面的每一个文件
                System.out.println("名称pathname:"+pathname.getAbsolutePath());
                //是文件，就返回
                if(pathname.isFile()){
                    return true;
                }
                return false;
            }
        });
        System.out.println("最后过滤得到的信息2");
        for(File f:filter2Files){
            System.out.println("过滤后的文件名称:"+f.getName());
        }
    }

  @Test
    public void rootTest(){
       File[] files=File.listRoots();
       for(File f:files){
           // c:\  d:\  E:\
           System.out.println("文件路径:"+f.getAbsolutePath());
       }
    }

  @Test
    public void pathClassTest(){
        File file1=new File("E:"+File.separator+"ideaWork"+File.separator+"Java2"+File.separator+"fileSrc"
                +File.separator+"Hello.txt");
        Path path=file1.toPath();
        System.out.println("输出:"+path.getFileName());
    }