Java中的文件目录操作

1. 使用FileOutputStream向文件中写入内容

package com;

import java.io.*;
import java.nio.charset.Charset;

public class HelloIO {	
	public static void main(String[] args) throws IOException{
		String fileName = "e:\\test.txt";
		
		/*File file = new File(fileName);
		
		//判断文件是否存在，如果存在则删除
 		if(file.exists()){		 
			System.out.println(String.format("file %s is exists",fileName));
			file.delete();
			System.out.println("deleted");
		}
		 */

		FileOutputStream out = null;
		String content = "hello IO 玉开";
		try{
			boolean append = true;
			out = new FileOutputStream(fileName,append);
			String charsetName = "utf-8";
			byte[] byteArray = content.getBytes(Charset.forName(charsetName));
			out.write(byteArray);
			System.out.println("done");
		}
		finally{
			if(out != null){
				out.close();
				out = null;
			}
		}
	}
}

 

2. 逐行读取文件内容

import java.io.*;

public class HelloFileReader {

	public static void main(String[] args) throws IOException{
		String fileName = "E:\\test.txt";
		InputStreamReader rdr = null;
		try{
			FileInputStream stream = new FileInputStream(fileName);
			rdr = new InputStreamReader(stream,"utf-8"); 
			
			//逐行读取类
			LineNumberReader lineRdr = new LineNumberReader(rdr);
			String line;
			
			while((line = lineRdr.readLine()) != null){
				System.out.println(line);
			}
			
			stream.close();
		}finally{
			if(rdr != null){
				rdr.close();
				rdr = null;
			}
		}
	}
	
}

 3. 创建或者列出文件目录

package org.zyk;

import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.util.Calendar;
import java.util.Date;

public class HelloJavaDir {
		public static void main(String[] args) throws IOException{
			String dir = "E:/test/test";
			File file = new File(dir);
			
			if(!file.exists()){
				//mkdirs可以创建多级目录
				file.mkdirs();
				System.out.println("create new dir");				
			}else{
				System.out.println("dir is exists");
				//这儿删除只是删除了最后一级目录
				//file.delete();
				//System.out.println("delete it");
			}
			
			/*在不确认目录是否存在的情况下创建文件*/
			String fileName ="e:/test/test/test.txt";
			File testFile = new File(fileName);
			if(testFile.exists()){
				System.out.println("testFile is exists");
			}else{
				File testParentFile = testFile.getParentFile();
				if(!testParentFile.exists()){
					//使用mkdirs可以创建多级目录
					testParentFile.mkdirs();
				}
				testFile.createNewFile();
				System.out.println("创建了testFile");
			}

			Date now = new Date();
			Calendar cal = Calendar.getInstance();
			cal.setTime(now);
			int year = cal.get(Calendar.YEAR);
			String strYear = String.valueOf(year);
			String dirYearName = dir + File.separator + strYear;
			//创建年目录
			File dirYear = new File(dirYearName);
			if(!dirYear.exists()){
				dirYear.mkdir();
				System.out.println("create year dir");
			}else{
				System.out.println("year dir exists");
			}
			
			String yearDefaultFileName = dirYearName + File.separator + "default.htm";
			File yearDefaultFile = new File(yearDefaultFileName);
			if(yearDefaultFile.exists()){
				System.out.println("yearDefaultFile exists");
			}else{
				yearDefaultFile.createNewFile();
				System.out.println("yearDefaultFile created");
			}
			
			//创建12个月的目录 
			for(int month = 1;month<=12;month++){
				String monthDirName = dirYearName + File.separator + String.format("%02d",month);
				File dirMonth = new File(monthDirName);
				//创建月的目录
				if(!dirMonth.exists()){
					dirMonth.mkdir();
					System.out.println("create month dir");
				}else{
					System.out.println("month dir exists");
				}
				
				//创建月的文件
				for(int fileIndex = 0;fileIndex<5;fileIndex ++){
					String monthFileName;
					if(fileIndex == 0)
						monthFileName = monthDirName + File.separator + "default.html";
					else
						monthFileName = monthDirName + File.separator + String.format("list-%d.html",fileIndex);
					File fileMonth = new File(monthFileName);
					if(!fileMonth.exists()){
						fileMonth.createNewFile();
						System.out.println("create month file");
					}else{
						System.out.println("month file exists");
					}
				}
			}
			
			//输出year目录下的所有文件和目录
			String[] yearChildren = dirYear.list();
			System.out.println("children of the yeardir :");
			for(String cFilePath : yearChildren){
				System.out.println("\t" + cFilePath);
			}
			
			//输出year目录下的所有文件和目录
			File[] yearChildrenFiles = dirYear.listFiles();
			System.out.println("children files of the yeardir :");
			for(File cFile :yearChildrenFiles){
				System.out.println("\t" + cFile.getAbsolutePath());
			}
			
			//输出year目录下的所有子目录
			//注意这个java抽象类实现，很方便
			FilenameFilter filterForFolder = new FilenameFilter(){
				@Override
				public boolean accept(File dir, String name) {
					File child = new File(dir.getAbsolutePath() + File.separator + name);
					
					return child.isDirectory();
				}
			};
			String[] filters = dirYear.list(filterForFolder);
			for(String filter : filters){
				System.out.println(filter);
			}
		}
}