Java常用基础技术
2012-06-18 15:02
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| java得到文件路径下的所有文件名 ] /* 4000 * @param 声明File对象,指定参数filePath */ File dir = new File(filePath); //返回此抽象路径下的文件 File[] files = dir.listFiles(); if (files == null) return; for (int i = 0; i < files.length; i++) { //判断此文件是否是一个文件 if (！files[i].isDirectory()) { System.out.println(files[i].getName()); } } -------------------------------- 1.创建文件: /** * 上传文件 * * @param file 上传文件实体 * @param filename 上传文件新命名 * @param dir 上传文件目录 * @return */ public static boolean uploadFile(File file, String dir, String filename) { boolean ret = false; try { if (file != null) { java.io.File filePath = new java.io.File(dir); if (!filePath.exists()) { filePath.mkdir(); } String target = dir + filename; FileOutputStream outputStream = new FileOutputStream(target); FileInputStream fileIn = new FileInputStream(file); byte[] buffer = new byte[1024]; int len; while ((len = fileIn.read(buffer)) > 0) { outputStream.write(buffer, 0, len); } fileIn.close(); outputStream.close(); ret = true; } } catch (Exception ex) { log.info("上传文件无法处理，请确认上传文件！"); } return ret; } --------------------------------- 删除文件: /** * 删除文件 * * @param filePathAndName 删除文件完整路径:d:/filedir/filename * @return */ public static boolean delFile(String filePathAndName) { boolean ret = false; try { new File(filePathAndName.toString()).delete(); ret = true; } catch (Exception e) { System.out.println("删除文件操作出错"); e.printStackTrace(); } return ret; } ---------------------------------------- 删除目录下全部文件: /** * 删除目录下的文件 * * @param dir 文件目录 d:/filedir/ * @return */ public static boolean delFiles(String dir) { boolean ret = false; try { File filePath = new File(dir);// 查询路径 String[] files = filePath.list();// 存放所有查询结果 int i = 0; for (i = 0; i < files.length; i++) { new java.io.File(dir + "/" + files[i]).delete(); } ret = true; } catch (Exception e) { e.printStackTrace(); } return ret; } -------------------------------------------- .判断文件是否存在 /** * 判断文件是否存在 * * @param filename * @return */ public static boolean isExist(String filename) { boolean ret = false; try { File file = new File(filename.toString()); if (file.exists()) { ret = true; } } catch (Exception e) { e.printStackTrace(); } return ret; } ------------------------------------------------- 根据制定路径，可以获取当前正在操作的文件的大小，容量为byte. import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; public class FileByte { private String filePath = "D:\\m07012600030000001_z.wav"; private void getFileByte(){ File f = new File(filePath) ; try{ FileInputStream fis = new FileInputStream(f) ; try { System.out.println(fis.available()) ; }catch(IOException e1){ e1.printStackTrace(); } }catch(FileNotFoundException e2){ e2.printStackTrace(); } } public static void main(String[] args) { FileByte fb = new FileByte(); fb.getFileByte(); } } ------------------------------------------------------- 如何用java获取网络文件的大小(多线程 import java.io.BufferedInputStream; import java.io.File; import java.io.FileNotFoundException; import java.io.FileOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.RandomAccessFile; import java.net.HttpURLConnection; import java.net.MalformedURLException; import java.net.URL; public class saveToFile { public void saveToFile(String destUrl, String fileName) throws IOException { FileOutputStream fos = null; BufferedInputStream bis = null; HttpURLConnection httpUrl = null; URL url = null; byte[] buf = new byte[2]; int size = 0; int s=0; //建立链接 url = new URL(destUrl); httpUrl = (HttpURLConnection) url.openConnection(); //连接指定的资源 httpUrl.connect(); //获取网络输入流 bis = new BufferedInputStream(httpUrl.getInputStream()); //建立文件 fos = new FileOutputStream(fileName); System.out.println("正在获取链接[" + destUrl + "]的内容...\n将其保存为文件[" + fileName + "]"); //保存文件 while ( (size = bis.read(buf)) != -1) { fos.write(buf, 0, size); //++s; System.out.println(size); //System.out.println(s/1024+"M"); } fos.close(); bis.close(); httpUrl.disconnect(); } //多线程文件下载程序: public class DownloadNetTest { private File fileOut; private java.net.URL url; private long fileLength=0; //初始化线程数 private int ThreadNum=5; public DownloadNetTest(){ try{ System.out.println("正在链接URL"); url=new URL("http://211.64.201.201/uploadfile/nyz.mp3"); HttpURLConnection urlcon=(HttpURLConnection)url.openConnection(); //根据响应获取文件大小 fileLength=urlcon.getContentLength(); if(urlcon.getResponseCode()>=400){ System.out.println("服务器响应错误"); System.exit(-1); } if(fileLength<=0) System.out.println("无法获知文件大小"); //打印信息 printMIME(urlcon); System.out.println("文件大小为"+fileLength/1024+"K"); //获取文件名 String trueurl=urlcon.getURL().toString(); String filename=trueurl.substring(trueurl.lastIndexOf('/')+1); fileOut=new File("D://",filename); } catch(MalformedURLException e){ System.err.println(e); } catch(IOException e){ System.err.println(e); } init(); } private void init(){ DownloadNetThread [] down=new DownloadNetThread[ThreadNum]; try { for(int i=0;i<ThreadNum;i++){ RandomAccessFile randOut=new RandomAccessFile(fileOut,"rw"); randOut.setLength(fileLength); long block=fileLength/ThreadNum+1; randOut.seek(block*i); down[i]=new DownloadNetThread(url,randOut,block,i+1); down[i].setPriority(7); down[i].start(); } //循环判断是否下载完毕 boolean flag=true; while (flag) { Thread.sleep(500); flag = false; for (int i = 0; i < ThreadNum; i++) if (!down[i].isFinished()) { flag = true; break; } }// end while System.out.println("文件下载完毕，保存在"+fileOut.getPath() ); } catch (FileNotFoundException e) { System.err.println(e); e.printStackTrace(); } catch(IOException e){ System.err.println(e); e.printStackTrace(); } catch (InterruptedException e) { System.err.println(e); } } private void printMIME(HttpURLConnection http){ for(int i=0;;i++){ String mine=http.getHeaderField(i); if(mine==null) return; System.out.println(http.getHeaderFieldKey(i)+":"+mine); } } //线程类 public class DownloadNetThread extends Thread{ private InputStream randIn; private RandomAccessFile randOut; private URL url; private long block; private int threadId=-1; private boolean done=false; public DownloadNetThread(URL url,RandomAccessFile out,long block,int threadId){ this.url=url; this.randOut=out; this.block=block; this.threadId=threadId; } public void run(){ try{ HttpURLConnection http=(HttpURLConnection)url.openConnection(); http.setRequestProperty("Range","bytes="+block*(threadId-1)+"-"); randIn=http.getInputStream(); } catch(IOException e){ System.err.println(e); } //////////////////////// byte [] buffer=new byte[1024]; int offset=0; long localSize=0; System.out.println("线程"+threadId+"开始下载"); try { while ((offset = randIn.read(buffer)) != -1&&localSize<=block) { randOut.write(buffer,0,offset); localSize+=offset; } randOut.close(); randIn.close(); done=true; System.out.println("线程"+threadId+"完成下载"); this.interrupt(); } catch(Exception e){ System.err.println(e); } } public boolean isFinished(){ return done; } } } /*public static void main(String[] args) { DownloadNetTest app=new DownloadNetTest(); } */ } ---------------------------- pom.xml里面声明java的jar dependency> <groupId>com.sun</groupId> <artifactId>tools</artifactId> <version>1.6.0< ersion> <scope>system</scope> <systemPath>C:/Program Files/Java k1.6.0_05 b/tools.jar</systemPath> </dependency> ---------------------------------------------- 获取的路径里有空格变成20%以后，用什么把这个还原 String path = "111120%"; path=path.replace（"20%"," "）; 13795111413 ---------------------------------------- 70 到 110 之间怎么随机呢？ int ss=(int)(71+Math.random()*(100-71+1)); System.out.println(ss); ------------------------------------------ 使用Calendar 处理时间格式 public static long parse(String dstr) { if (dstr == null || dstr.length() == 0) { return 0; } if (NumberUtils.isNumber(dstr)) { return Long.parseLong(dstr) * 86400000; } String year = ""; String month = ""; String day = ""; int flag = 1; char prech = 0; dstr=dstr.trim(); for (char ch : dstr.toCharArray()) { if (ch <= '9' && ch >= '0') { switch (flag) { case 1: year += ch; break; case 2: month += ch; break; case 3: day += ch; break; } } else { if (prech <= '9' && prech >='0') flag++; } prech = ch; } int y = year.equals("") ? 1970 : Integer.parseInt(year); int m = month.equals("") ? 1 : Integer.parseInt(month); int d = day.equals("") ? 1 : Integer.parseInt(day); Calendar cal = Calendar.getInstance(); cal.set(Calendar.YEAR, y); cal.set(Calendar.MONTH, m-1); cal.set(Calendar.DAY_OF_MONTH, d); return cal.getTimeInMillis(); } ------------------------------- 输出任何格式的时间 截取时间 public void InterceptionTime() { //先制造一个完整的时间. DateFormat allTimeFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.SSS"); Date allTime = null; try { allTime = allTimeFormat.parse("2009-06-05 10:12:24.577"); } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } //截取时间,也可以使用下边的SimpleDateFormat DateFormat format = new SimpleDateFormat("HH:mm:ss.SSS"); String value = format.format(allTime); System.out.println(value); SimpleDateFormat dateFormat = new SimpleDateFormat ("yyyy-MM-dd"); String value2=dateFormat.format(allTime); System.out.println(value2); } --------------------------------- 转换2进制， lang包中Integer类中有个static String toBinaryString(int i) ---------------------------------------------- oracle怎么判断表是否存在 select count(*) into num from USER_TABLES where TABLE_NAME='T2' if num>0 then --存在 end if; ------------------------------------------------------ 记住帐号和密码 JS // 存cookie Cookie user = new Cookie("User_Name", "hsyd"); Cookie pass = new Cookie("Password", "hsyd"); response.addCookie(user); response.addCookie(pass); // 取cookie Cookie[] cookies = request.getCookies(); // ...找到匹配的cookie即可。 |
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