java开发之File类详细使用方法介绍

/*
 - File的构造函数
 - */
 public static void main(String[] args) {
  //File(String pathname) 将指定路径名转换成一个File对象
  File file = new File("D:\\1.txt");
  System.out.println(file);
  //File(String parent,String child) 根据指定的父路径和文件路径创建File对象
  File file1 = new File("D:\\a","1.txt");
  System.out.println(file1);
  //File(File parent,String child) 根据指定的父路径对象和文件路径创建File对象
  File parent = new File("D:\\a");
  File file2 = new File(parent, "1.txt");
  System.out.println(file2);
  File file3 = new File(new File("D:\\a"),"1.txt");
  System.out.println(file3);

 }

public static void main(String[] args) throws IOException {
 File file = new File("D:\\a\\1.txt");
 File file1 = new File("1.txt");
 boolean flag = file1.createNewFile();
 System.out.println(flag);

 File file2 = new File("b");
 boolean flag2 = file2.mkdir();
 System.out.println(flag);

 File file3 = new File("c\\d\\e");
 boolean d = file1.mkdir();
 boolean c = file1.mkdirs();
 System.out.println(d);
 System.out.println(c);
 File file4 = new File("c.txt");
 System.out.println(file4.mkdir());

 File file5 = new File("b");
 System.out.println(file2.delete());
}

public static void main(String[] args) throws IOException {
 // method();
 // method2();
 // method3();
 // method4();
}
//判断文件是否存在
public static void method() throws IOException {
 File file = new File("a.txt");
 file.createNewFile();
 boolean flag = file.exists();
 System.out.println(flag);
}
//判断当前路径是否为绝对路径
public static void method2() throws IOException{
 File file = new File("D:\\a\\1.txt");
 boolean flag = file.isAbsolute();
 System.out.println(flag);
}
//判断当前是文件夹还是文件
public static void method3() throws IOException{
 File file = new File("1.txt");
 File file1 = new File("b");
 file1.mkdir();
 boolean flag = file.isDirectory();
 boolean flag2 = file1.isFile();
 System.out.println(flag);
 System.out.println(flag2);
}
//判断当前路径是否为隐藏文件
public static void method4() throws IOException{
 File file = new File("D:\\a\\1.txt");
 System.out.println(file.isHidden());
}

public static void main(String[] args) throws IOException {
 // method();
 // method2();
 // method3();
 // method4();
}
public static void method(){
 File file = new File("D:\\a\\1.txt");
 File file1 = new File("1.txt");
 //以File对象返回的形式返回当前File对象所指向的绝对路径
 System.out.println(file1.getAbsoluteFile());
 //返回File对象所指向的绝对路径
 System.out.println(file1.getAbsolutePath());
}
public static void method2() throws IOException {
 File file = new File("a.txt");
 File file1 = new File("b","c.txt");
 System.out.println(file1.createNewFile());

 File parent = new File("b");
 File file2 = new File(parent,"c.txt");
 if (!parent.exists()){
  parent.mkdirs();
 }
 System.out.println(file2.createNewFile());
 System.out.println(file2.getParent());
 System.out.println(file2.getParentFile());
}
public static void method3() throws IOException{
 File file = new File("1.txt");
 File file1 = new File("D:\\a\\1.txt");
 File file2 = new File("b");

 System.out.println(file.getName());
 System.out.println(file1.getName());
 System.out.println(file2.getName());

 System.out.println(file.getPath());
 System.out.println(file1.getPath());
 System.out.println(file2.getPath());

 System.out.println(file.lastModified());
 Date date = new Date(1556085068524L);
 System.out.println(date.toLocaleString());

 System.out.println(file.length());
 System.out.println(file2.length());
}
public static void method4() throws IOException{
 File file = new File("a.txt");
 File file1 = new File("e.txt");
 System.out.println(file.renameTo(file1));
}

public static void main(String[] args) {
 //method();
 // method2();
 //method3();
}

public static void method(){
 File file = new File("b");
 File file1 = new File("D:\\QQ\\1916247350");
 File file2 = new File("e.txt");
 String[] files = file1.list();
 for (int i=0;i<files.length;i++){
  System.out.println(files[i]);
 }
}
public static void method2(){
 File file = new File("b");
 File file1 = new File("D:\\QQ\\1916247350");
 File file2 = new File("e.txt");

 File[] files = file1.listFiles();
 for (File file3 : files) {
  System.out.println(file3.getName());
 }
}
public static void method3(){
 File[] files = File.listRoots();
 for (File file : files) {
  System.out.println(file);
 }
}

public static void main(String[] args) {
 File file = new File("D:\\IDEA\\IDEAprogram");
 method(file);
}
public static void method(File file){
//判断文件是够是目录文件
 if (file.isDirectory()){
  File[] files = file.listFiles();
  for (File file1 : files) {
  //判断是否为文件
   if (file1.isFile()){
   //判断文件是否是以.java结尾的文件
    if (file1.getName().endsWith(".java")){
     System.out.println(file1.getName());
    }
   }else if (file1.isDirectory()){ 
   //回调，遍历file1
    method(file1);
   }
  }
 }
}

public static void main(String[] args) {
 File file = new File("D:\\a");
 method(file);
}
//删除指定目录下的文件
public static void method(File file){
 //删除自己所有的子文件和子目录
 //获取子文件和子目录
 if (file.isDirectory()){
  File[] files = file.listFiles();
  for (File file1 : files) {
   if (file1.isFile()){
    System.out.println(file1.getName());
    //干掉它
    file1.delete();
   }else if (file1.isDirectory()){
    //继续查看
    method(file1);
   }
  }
  //干掉自己
  System.out.println(file.getName());
  file.delete();
 }
}