IO，File对象-构造函数和常用方法

 1 import java.io.File;
 2 import java.text.DateFormat;
 3 import java.util.Date;
 4 
 5 public class FileDemo {
 6     public static void main(String[] args) throws Exception{
 7         creatAndDelect();
 8         getDemo();
 9         isDmeo();
10         reNameToName();
11         listDemo();
12         listRootDmeo();
13     }
14     // 1， 获取
15     public static void getDemo() {
16         // 文件或文件夹名称
17         File file = new File("D:/1.txt");
18         // 绝对路劲
19         String name = file.getName();
20         System.out.println(name);
21         // 相对路径
22         String absolutePath = file.getAbsolutePath();
23         System.out.println(absolutePath);
24         // 文件大小
25         long len = file.length();
26         System.out.println(len);
27         // 最后一次修改时间
28         long time = file.lastModified();
29         Date date = new Date(time);
30         DateFormat dateFormat = DateFormat.getDateTimeInstance(DateFormat.FULL, DateFormat.FULL);
31         String str_time = dateFormat.format(date);
32         System.out.println(str_time);
33     }
34     // 2， 创建和删除
35     public static void creatAndDelect() throws Exception{
36         File file = new File("D:\\2.txt");
37         boolean b = file.mkdirs();
38         System.out.println(b);
39         System.out.println(file.delete());
40         //文件
41 //        File file2 = new File("D:\\3.txt");
42 //        boolean b1 = file2.createNewFile();
43 //        boolean b2 = file2.delete();
44 //        System.out.println(b1);
45 //        System.out.println(b2);
46     }
47     // 3， 判断
48     public static void isDmeo() {
49         File file = new File("D:\\1.txt");
50         //存在
51         System.out.println("exists:" + file.exists());
52         //目录
53         System.out.println("isDirectory:" + file.isDirectory());
54         //文件
55         System.out.println("isFile:" + file.isFile());
56         //隐藏
57         System.out.println("isHidden:" + file.isHidden());
58     }
59     // 4， 重命名
60     public static void reNameToName() {
61         File file = new File("D:\\1.txt");
62         File f = new File("D:\\4.txt");
63         System.out.println(file.renameTo(f));
64     }
65     // 5， 系统根目录和容量获取
66     public static void listRootDmeo() {
67         File file[] = File.listRoots();
68         for(File f : file) {
69             System.out.println(f);
70             System.out.println("FreeSpace:" + f.getFreeSpace());
71             System.out.println("TotalSpace:" + f.getTotalSpace());
72             System.out.println("UsableSpace:" + f.getUsableSpace());
73         }
74     }
75     
76     public static void listDemo() {
77         File file = new File("C:\\");
78         String names[] = file.list();
79         for(String name : names) {
80             System.out.println(name);
81         }
82     }
83 }