java IO

IO流
一、 列出指定目录下所有文件

import java.io.*;
class IOTest1 
{
	public static void main(String[] args) 
	{
		File dir = new File("D:\\图库");
		new IOTest1().showDir(dir, 1);
	}
	public void showDir(File dir, int level) {
		File[] files = dir.listFiles();
		StringBuilder sb = new StringBuilder();
		sb.append("|--");
		for(int i = 1; i < level; i++) {
			sb.insert(0,"   ");
		}
		for(int i = 0; i < files.length; i++) {
			System.out.println(sb.toString() + files[i].getName());
			if(files[i].isDirectory()) {
				 showDir(files[i], level + 1);
			}
		}
	}
}

递归使用的两个条件：1、要有判断，能够让程序结束；2、注意递归运算的次数，避免内存溢出。
二、 删除文件夹下面所有目录及文件

import java.io.*;
class DeleteDemo 
{
	public static void main(String[] args) 
	{
		File dir = new File("d:\\Test");
		deleteAll(dir);
	}
	public static void deleteAll(File dir) {
		File[] files = dir.listFiles();
		for(int i = 0; i < files.length; i++) {
			if(files[i].isDirectory())
				deleteAll(files[i]);
			else
				System.out.println(files[i].toString() + "==file==" + files[i].delete());
		}
		System.out.println(dir + "--dir--" + dir.delete());
	}
}

三、 Properties类的使用(继承Hashtable，是集合类)

import java.util.*;
class PropertiesTest 
{
	public static void main(String[] args) 
	{
		getAndSet();
	}
	public static void getAndSet() {
		Properties prop = new Properties();
		prop.setProperty("qin","rui");
		prop.setProperty("c","yuan");
		//System.out.println(prop);
		Set<String> keys = prop.stringPropertyNames();
		for(String key : keys) {
			System.out.println(key + "==" + prop.getProperty(key));
		}
	}
}

四、 Properties类结合IO流读写配置文件

import java.util.*;
import java.io.*;
class PropertiesIOTest 
{
	public static void main(String[] args) 
	{
		Properties props = new Properties();
		InputStreamReader fr = null;
		try
		{
			fr = new InputStreamReader(new FileInputStream("D:\\java1\\IO\\info.txt"));
			//从文件中获取配置信息存入Properties中
			props.load(fr);
			getInfo(props);
			setInfo(props);
			getInfo(props);
		}
		catch (IOException e)
		{
			e.printStackTrace();
		} finally {
			try {
				if(fr != null) {
					fr.close();
					fr = null;
				}
				
			}
			catch (IOException e){
				e.printStackTrace();
			}
		}
	}
	public static void getInfo(Properties props) {
		//使用stringPropertyNames()获取，配置信息的键，返回一个Set集合
		Set<String> keys = props.stringPropertyNames();
		for(String key : keys) {
			System.out.println(key + "==" + props.getProperty(key));
		}
	}
	//设置配置信息并存入文件中
	public static void setInfo(Properties props) throws IOException {
		props.setProperty("love","yuanrui");
		PrintWriter pw = new PrintWriter(new PrintStream("D:\\java1\\IO\\info.txt"));
		//使用store方法把更改的信息存入文件中，会自动调用list()方法
		props.store(pw,null);
		//关闭IO流是必须要做的操作，减少内在占用
		pw.close();
	}
}

五、 软件使用计数器

import java.util.*;
import java.io.*;
class countDemo 
{
	public static void main(String[] args) throws IOException
	{
		Properties props = new Properties();
		File file = new File("conf.ini");
		//judge whether the file exist, if not creat a new one
		if(!file.exists()) {
			file.createNewFile();
		}
		BufferedReader br = new BufferedReader(new FileReader(file));
		//load the data from the file
		props.load(br);

		//declare a value to note the use time
		int count = 0;
		String value = props.getProperty("time");
		if(value != null) { 
			count = Integer.parseInt(value);
			if(count >= 5) {
				System.out.println("您的使用时间快到！请注册后再继续使用！");
				return ;
			}
		}
		count++;
		props.setProperty("time",count + "");

		//declare a writer to save the data to the file
		BufferedWriter bw = new BufferedWriter(new FileWriter(file));
		props.store(bw , null);
		System.out.println(props);
	}
}

六、 使用SequenceInputStream将多个文件整合

import java.io.*;
import java.util.*;
class SequenceDemo 
{
	public static void main(String[] args) throws IOException
	{
		//save the inputstream in the vector
		Vector<FileInputStream> vec = new Vector<FileInputStream>();
		vec.add(new FileInputStream("info.txt"));
		vec.add(new FileInputStream("conf.ini"));
		//use the method elements() to get the enum
		Enumeration<FileInputStream> en = vec.elements();

		//create a sequenceInputStream contains more than one inputStream
		SequenceInputStream sis = new SequenceInputStream(en);
		FileOutputStream fos = new FileOutputStream("add.ini");

		//create a space to restore the data read from the file
		byte[] bt = new byte[1024];
		int len = 0;
		while((len = sis.read(bt)) > 0) {
			fos.write(bt, 0, len);
		}
		sis.close();
		fos.close();
	}
}

七、 文件切割

import java.io.*;
class SplitDemo 
{
	public static void main(String[] args) throws IOException
	{
		splitFile();
	}
	public static void splitFile() throws IOException {
		File file = new File("D:\\图库\\我的图片\\个人图库\\八里沟\\1-4.jpg");
		FileInputStream fis = new FileInputStream(file);
		FileOutputStream fos = null;
		int len = 0;
		int count = 1;
		byte[] bt = new byte[1024*1024];
		while((len = fis.read(bt)) != -1) {
			fos = new FileOutputStream("D:\\java1\\IO\\split\\" + (count++) + ".part");
			fos.write(bt, 0, len);
			fos.close();
		}
		if(fos != null)
			fos.close();
		fis.close();
	}
}