java 读写工具类

public class Util {
	/**
	 * 读文件到内存，返回的编码方式是utf-8
	 * @param fileName 
	 * @return
	 * 2011-11-2
	 */
	public static String readFile(String fileName){
		File file = new File(fileName);
	    Reader reader = null;
	    StringBuffer buf = new StringBuffer();
	    String outString ="";
	    try {
	    	//以utf-8的形式读入文件
	        reader = new InputStreamReader(new FileInputStream(file),"utf-8");
	        int tempchar;
	        while ((tempchar = reader.read()) != -1) {
	            if (((char) tempchar) != '\r') {
	            	char aa = (char) tempchar;
	                buf.append((char) tempchar);
	            }
	        }
	        outString = buf.toString();
	        //判断读入的文件编码方式是否是gb2312的形式，要是不是，重新以gb2312的形式读入文件，之后再改成utf-8的形式
	        if(buf.toString().contains("charset=gb2312")){
	        	buf = new StringBuffer();
	        	//以gb2312的形式读入文件
	        	reader = new InputStreamReader(new FileInputStream(file),"gb2312");
		        while ((tempchar = reader.read()) != -1) {
		            if (((char) tempchar) != '\r') {
		            	char aa = (char) tempchar;
		                buf.append((char) tempchar);
		            }
		        }
		        outString = Util.code2code(buf.toString(), "gb2312", "utf-8");
		    }
	        reader.close();
	    } catch (Exception e) {
	        e.printStackTrace();
	    }
		return outString;
	}
	/**
	 * 输出文件
	 * @param fileName
	 * @param s
	 * 2011-11-2
	 */
	public static void writerFile(String fileName,String s){
		String mkd = fileName.substring(0, fileName.lastIndexOf("\\"));
		//生成目录
		new File(mkd).mkdirs();
		FileWriter fw;
		try {
			fw = new FileWriter(fileName);
			fw.write(s);
			fw.flush();  
			fw.close();
		} catch (IOException e) {
			e.printStackTrace();
		} 
	}
	
	/**
	 * 读目录，把目录下的文件名生成List
	 * @param delpath
	 * @return
	 * 2011-11-2
	 */
	public static List readDirectory(String delpath){
		List list = new ArrayList();
		File file = new File(delpath);
		String[] monthlist = file.list();
		int l=1;
		for (int i = 0; i < monthlist.length; i++) {
			
			File monthfile = new File(delpath + "\\" + monthlist[i]);
			String monthpath=monthfile.getPath();
			
			String[] daylist = monthfile.list();
			for(int j = 0 ; j < daylist.length ; j++){
				File dayfile = new File(monthpath + "\\" + daylist[j]);
				String[] contentlist = dayfile.list();
				String datepath=dayfile.getPath();
				if(contentlist!=null){
					for(int k =0;k < contentlist.length;k++){
						File content = new File(datepath + "\\" + contentlist[k]);
						String path = content.getPath();
						list.add(content.getPath());
						
						System.out.println(l++);
//						System.out.println(content.getPath());
					}
				}
				
			}
			
		}
		System.out.println("******");
		return list;
	}
	
	/**
	 * 编码转换
	 * @param strIn 要转换的字符串
	 * @param sourceCode 原来的编码方式
	 * @param targetCode 目标编码方式
	 * @return
	 * 2011-11-2
	 */
	public static String code2code(String strIn, String sourceCode,String targetCode) {
		String strOut = null;
		if (strIn == null || (strIn.trim()).equals(""))
			return strIn;
		try {
			byte[] b = strIn.getBytes(sourceCode);
			String str = new String(b, sourceCode);
			byte[] c = str.getBytes(targetCode);
			strOut = new String(c, targetCode);
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
		return strOut;
	}
}