IO，File对象-构造函数和常用方法

 import java.io.File;
 import java.text.DateFormat;
 import java.util.Date;

 public class FileDemo {
     public static void main(String[] args) throws Exception{
         creatAndDelect();
         getDemo();
         isDmeo();
         reNameToName();
         listDemo();
         listRootDmeo();
     }
     // 1， 获取
     public static void getDemo() {
         // 文件或文件夹名称
         File file = new File("D:/1.txt");
         // 绝对路劲
         String name = file.getName();
         System.out.println(name);
         // 相对路径
         String absolutePath = file.getAbsolutePath();
         System.out.println(absolutePath);
         // 文件大小
         long len = file.length();
         System.out.println(len);
         // 最后一次修改时间
         long time = file.lastModified();
         Date date = new Date(time);
         DateFormat dateFormat = DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.FULL);
         String str_time = dateFormat.format(date);
         System.out.println(str_time);
     }
     // 2， 创建和删除
     public static void creatAndDelect() throws Exception{
         File file = new File("D:\\2.txt");
         boolean b = file.mkdirs();
         System.out.println(b);
         System.out.println(file.delete());
         //文件
 //        File file2 = new File("D:\\3.txt");
 //        boolean b1 = file2.createNewFile();
 //        boolean b2 = file2.delete();
 //        System.out.println(b1);
 //        System.out.println(b2);
     }
     // 3， 判断
     public static void isDmeo() {
         File file = new File("D:\\1.txt");
         //存在
         System.out.println("exists:" + file.exists());
         //目录
         System.out.println("isDirectory:" + file.isDirectory());
         //文件
         System.out.println("isFile:" + file.isFile());
         //隐藏
         System.out.println("isHidden:" + file.isHidden());
     }
     // 4， 重命名
     public static void reNameToName() {
         File file = new File("D:\\1.txt");
         File f = new File("D:\\4.txt");
         System.out.println(file.renameTo(f));
     }
     // 5， 系统根目录和容量获取
     public static void listRootDmeo() {
         File file[] = File.listRoots();
         for(File f : file) {
             System.out.println(f);
             System.out.println("FreeSpace:" + f.getFreeSpace());
             System.out.println("TotalSpace:" + f.getTotalSpace());
             System.out.println("UsableSpace:" + f.getUsableSpace());
         }
     }

     public static void listDemo() {
         File file = new File("C:\\");
         String names[] = file.list();
         for(String name : names) {
             System.out.println(name);
         }
     }
 }