JAVA中File的相关操作

1. Creation of a file if it does not exist; Deletion of a file if it already exists.

   package com.han;
   
   import java.io.File;
   
   /**
    * Creation of a file if it does not exist;
    * Deletion of a file if it already exists.
    * @author han
    *
    */
   public class FileTest {
   
   	public static void main(String[] args) {
   		// TODO Auto-generated method stub
   		File file=new File("/home/han/Documents","word.txt");
   		if(file.exists()){
   			System.out.println(file.getPath());
   			file.delete();
   			System.out.println("文件已删除");
   		}else{
   			try{
   				file.createNewFile();
   				System.out.println("文件已创建");
   			}catch(Exception e){
   				e.printStackTrace();
   			}
   		}
   
   	}
   
   }
   

   
   
   
2. Get a specified file properties, including its name, length, and existence or if it is hidden.

   package com.han;
   
   import java.io.File;
   
   /**
    * Get a specified file properties, 
    * including its name, length, and existence or if it is hidden.
    * @author han
    *
    */
   public class FileTest2 {
   
   	public static void main(String[] args) {
   		// TODO Auto-generated method stub
   		File file=new File("/home/han/Documents","word.txt");
   		if(file.exists()){
   			String name=file.getName();
   			long length=file.length();
   			boolean hidden=file.isHidden(); //if the file is hidden or not.
   			System.out.println("文件名称： "+name);
   			System.out.println("文件长度： "+length);
   			System.out.println("该文件是隐藏文件吗？ "+hidden);
   		}else{
   			try{
   				System.out.println("该文件不存在");
   			}catch(Exception e){
   				e.printStackTrace();
   			}
   		}
   	}
   
   }
   

   
   
   
3. write a string content to a text file using a FileInputStream and FileOutputStream

   package com.han;
   
   import java.io.*;
   
   /**
    * write a string content to a text file 
    * using a FileInputStream and FileOutputStream
    * @author han
    *
    */
   public class FileTest3 {
   	public static void main(String[] args) {
   		// TODO Auto-generated method stub
   		File file=new File("/home/han/Documents","word.txt");
   		try{
   			FileOutputStream out=new FileOutputStream(file); //创建输出流
   			byte[] content_to_output="我有一只小毛驴，我从来也不骑。".getBytes();
   			out.write(content_to_output);
   			out.close(); //关闭输出流
   		}catch(Exception e){
   			e.printStackTrace();
   		}
   		
   		try{
   			FileInputStream in=new FileInputStream(file); //创建输入流
   			byte[] content_to_input=new byte[1024];
   			int len=in.read(content_to_input);
   			in.close(); //关闭输入流
   			System.out.println(new String(content_to_input,0,len));
   			System.out.println("文件长度为： "+len);
   		}catch(Exception e){
   			e.printStackTrace();
   		}
   	}
   }
   

   
   
   
4. Rename a file.

   package com.han;
   
   import java.io.*;
   
   /**
    * Rename a file.
    * @author han
    *
    */
   public class FileTest4 {
   	public static void main(String[] args) {
   		/*Use to renameTo() method of the File class to complete the rename job*/
   		File file=new File("/home/han/Documents","word.txt");
   		File file_renamed=new File("/home/han/Documents","word_renamed.txt");
   		try{
   			FileOutputStream out=new FileOutputStream(file); //创建输出流
   			byte[] content_to_output="我有一只小毛驴，我从来也不骑。".getBytes();
   			out.write(content_to_output);
   			out.close(); //关闭输出流
   			file.renameTo(file_renamed);
   		}catch(Exception e){
   			e.printStackTrace();
   		}
   		/*Use the stream to copy a file to another*/
   		try{
   			FileInputStream in=new FileInputStream(file_renamed); //创建输入流
   			File file_copy=new File("/home/han/Documents","word_copy.txt");
   			FileOutputStream out_copy=new FileOutputStream(file_copy); //创建副本输出流
   			/*int input_byte=in.read(); 
   			while(input_byte!=-1){
   				out_copy.write(input_byte);
   				input_byte=in.read();
   			}*/
   			int input_byte=0;
   			while((input_byte=in.read())!=-1){ //(input_byte=in.read())!=-1 这种形式要会使用
   				out_copy.write(input_byte);
   			}
   			out_copy.close(); //关闭副本输出流
   			in.close(); //关闭输入流
   			System.out.println("副本文件名称为： "+file_copy.getName());
   			System.out.println("副本文件长度为： "+file_copy.length());
   			System.out.println("副本文件是隐藏文件吗？ "+file_copy.isHidden());
   		}catch(Exception e){
   			e.printStackTrace();
   		}
   	}
   }
   

   
   
   

5. write a string content to a specified text file. and then read it to the default command screen.

   package com.han;
   
   import java.io.*;
   
   /**
    * write a string content to a specified text file.
    * and then read it to the default command screen.
    * <p>
    * It used the FileReader and FileWriter, 
    * moreover, the BufferedReader and BufferedWriter.
    * @author han
    *
    */
   public class FileTest5 {
   
   	/**
   	 * @param args
   	 */
   	public static void main(String[] args) {
   		// TODO Auto-generated method stub
   		String[] content={"好久不见","最近好吗","常联系"};
   		File file=new File("/home/han/Documents","word.txt");
   		try {
   			FileWriter out=new FileWriter(file);
   			BufferedWriter bw=new BufferedWriter(out);
   			for (int i=0;i<content.length;i++){
   				bw.write(content[i]);
   				bw.newLine();
   			}
   			bw.close();
   			out.close();
   		} catch (IOException e) {
   			// TODO Auto-generated catch block
   			e.printStackTrace();
   		}
   		try {
   			FileReader in=new FileReader(file);
   			BufferedReader br=new BufferedReader(in);
   			String s=null;
   			int i=0;
   			while((s=br.readLine())!=null){
   				System.out.println("第"+(i+1)+"行： "+s);
   				i++;
   			}
   			br.close();
   			in.close();
   		} catch (IOException e) {
   			// TODO Auto-generated catch block
   			e.printStackTrace();
   		}
   		
   	}
   
   }
   

   
   

   It used the FileReader and FileWriter, moreover, the BufferedReader and BufferedWriter.