import java.io.*;

public class Demo{
    public static void main(String[] args){
          String filename="myfile.txt"; 
          String path="E:/mydir1/mkdir2"; 
          try{
                File dir = new File(path); 
                if(!dir.exists())
                    dir.mkdirs();
                
                File file=new File(path+File.separator+filename);
                if(!file.exists())
                    file.createNewFile();
          }catch(Exception e){
                e.printStackTrace();
          }

          System.out.println("Done");
    }
}

import java.io.*;   
class test{  
public static void main(String [] args){  
  String separator="\\";  
  String filename="myfile.txt";  
  String directory="mydir1"+separator+"mydir2";  
  File f=new File(directory,filename);  
  if(f.exists()){  
   System.out.println("文件名："+f.getAbsolutePath());  
   System.out.println("文件大小："+f.length());  
  }else{  
   f.getParentFile().mkdirs();  
   try{  
   f.createNewFile();  
   }catch(IOException e){  
   e.printStackTrace();  
   }  
   }  
  }  
}

import java.io.*;

public class Overloading {
    public static void main(String[] args) {
        String separator = ".separator";
        String filename = "myfile.txt";
        String directory = "mydir1" + separator + "mydir2";
        File f = new File(directory, filename);
        if (f.exists()) {
            System.out.println("文件名：" + f.getAbsolutePath());
            System.out.println("文件大小：" + f.length());
        } else {
            f.getParentFile().mkdirs();
            try {
                f.createNewFile();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

import java.io.File;

public class Files {
   
    public static void main(String []args)
    {
       Files.setFilesName("d:/");
    }
    public static void setFilesName(String url){
        
        File file=new File(url);
        File[] fis =file.listFiles();
        
        for(int i=0;i<fis.length;i++){
            if(fis[i].isFile()){
                System.out.println(fis[i].getName());
            }else{
                Files.setFilesName(fis[i].getAbsolutePath());
            }
        }
    }
}