public static boolean createFile(String filePath){ 
  boolean result = false; 
  File file = new File(filePath); 
  if(!file.exists()){ 
    try { 
      result = file.createNewFile(); 
    } catch (IOException e) { 
      e.printStackTrace(); 
    } 
  } 
   
  return result; 
} 

public static boolean createDirectory(String directory){ 
  boolean result = false; 
  File file = new File(directory); 
  if(!file.exists()){ 
    result = file.mkdirs(); 
  } 
   
  return result; 
} 

public static boolean deleteFile(String filePath){ 
  boolean result = false; 
  File file = new File(filePath); 
  if(file.exists() && file.isFile()){ 
    result = file.delete(); 
  } 
   
  return result; 
} 

public static void deleteDirectory(String filePath){ 
  File file = new File(filePath); 
  if(!file.exists()){ 
    return; 
  } 
   
  if(file.isFile()){ 
    file.delete(); 
  }else if(file.isDirectory()){ 
    File[] files = file.listFiles(); 
    for (File myfile : files) { 
      deleteDirectory(filePath + "/" + myfile.getName()); 
    } 
     
    file.delete(); 
  } 
} 

public static String readFileByBytes(String filePath){ 
  File file = new File(filePath); 
  if(!file.exists() || !file.isFile()){ 
    return null; 
  } 
   
  StringBuffer content = new StringBuffer(); 
   
  try { 
    byte[] temp = new byte[1024]; 
    FileInputStream fileInputStream = new FileInputStream(file); 
    while(fileInputStream.read(temp) != -1){ 
      content.append(new String(temp)); 
      temp = new byte[1024]; 
    } 
     
    fileInputStream.close(); 
  } catch (FileNotFoundException e) { 
    e.printStackTrace(); 
  } catch (IOException e) { 
    e.printStackTrace(); 
  } 
   
  return content.toString(); 
} 

public static String readFileByChars(String filePath){ 
  File file = new File(filePath); 
  if(!file.exists() || !file.isFile()){ 
    return null; 
  } 
   
  StringBuffer content = new StringBuffer(); 
  try { 
    char[] temp = new char[1024]; 
    FileInputStream fileInputStream = new FileInputStream(file); 
    InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream, "GBK"); 
    while(inputStreamReader.read(temp) != -1){ 
      content.append(new String(temp)); 
      temp = new char[1024]; 
    } 
     
    fileInputStream.close(); 
    inputStreamReader.close(); 
  } catch (FileNotFoundException e) { 
    e.printStackTrace(); 
  } catch (IOException e) { 
    e.printStackTrace(); 
  } 
   
  return content.toString(); 
} 

public static List<String> readFileByLines(String filePath){ 
  File file = new File(filePath); 
  if(!file.exists() || !file.isFile()){ 
    return null; 
  } 
   
  List<String> content = new ArrayList<String>(); 
  try { 
    FileInputStream fileInputStream = new FileInputStream(file); 
    InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream, "GBK"); 
    BufferedReader reader = new BufferedReader(inputStreamReader); 
    String lineContent = ""; 
    while ((lineContent = reader.readLine()) != null) { 
      content.add(lineContent); 
      System.out.println(lineContent); 
    } 
     
    fileInputStream.close(); 
    inputStreamReader.close(); 
    reader.close(); 
  } catch (FileNotFoundException e) { 
    e.printStackTrace(); 
  } catch (IOException e) { 
    e.printStackTrace(); 
  } 
   
  return content; 
} 

public static void writeFileByFileOutputStream(String filePath, String content) throws IOException{ 
  File file = new File(filePath); 
  synchronized (file) { 
    FileOutputStream fos = new FileOutputStream(filePath); 
    fos.write(content.getBytes("GBK")); 
    fos.close(); 
  } 
} 

public static void writeFileByBufferedOutputStream(String filePath, String content) throws IOException{ 
  File file = new File(filePath); 
  synchronized (file) { 
    BufferedOutputStream fos = new BufferedOutputStream(new FileOutputStream(filePath)); 
    fos.write(content.getBytes("GBK")); 
    fos.flush(); 
    fos.close(); 
  } 
} 

public static void writeFileByFileWriter(String filePath, String content) throws IOException{ 
    File file = new File(filePath); 
    synchronized (file) { 
      FileWriter fw = new FileWriter(filePath); 
      fw.write(content); 
      fw.close(); 
    } 
  } 

import java.io.File;

public class CreateDir {
  public static void main(String args[]) {
   String dirname = "/tmp/user/java/bin";
   File d = new File(dirname);
   // Create directory now.
   d.mkdirs();
 }
}

import java.io.File;

public class ReadDir {
  public static void main(String[] args) {

   File file = null;
   String[] paths;

   try{   
     // create new file object
     file = new File("/tmp");

     // array of files and directory
     paths = file.list();

     // for each name in the path array
     for(String path:paths)
     {
      // prints filename and directory name
      System.out.println(path);
     }
   }catch(Exception e){
     // if any error occurs
     e.printStackTrace();
   }
  }
}

test1.txt
test2.txt
ReadDir.java
ReadDir.class