java日常笔记2016-12-27

1：File.separator

File file1 = new File (“C:\tmp\test.txt”);

File myFile = new File(“C:” + File.separator + “tmp” + File.separator, “test.txt”);

2：过滤器   FileFilter

File[] ff = f.listFiles(new FileFilter() {}

3：两种流（字节流、包装流）

is = new FileInputStream(f);int value = -1;while((value=is.read())!=-1){System.out.println((char)value);}

is = new FileInputStream(f);int value = -1;byte[] tong = new byte[512];while((value=is.read(tong)) !=-1){String string = new String(tong, 0, value,"GBK");System.out.println(string);}

4：类路径加载资源

第一种：获取类加载的根路径   D:\git\daotie\daotie\target\classesFile f = new File(this.getClass().getResource("/").getPath());

第三种：  file:/D:/git/daotie/daotie/target/classes/URL xmlpath = this.getClass().getClassLoader().getResource("");

5：加载属性文件（properties文件、默认十六机制写中文会自动转码、写注释#）

6：

//资源路径有两种方式， //1:一种以 / 开头，则这样的路径是指定绝对路径，//2:如果不以 / 开头， 则路径是相对与这个class所在的包的public class Relation_Absolute {public static void main(String[] args) throws Exception {//绝对路径/*File file = new File("./src/test20161227/text.txt");System.out.println(file.length()); System.out.println(file.getAbsolutePath());*///相对路径/*InputStream is = Relation_Absolute.class.getClassLoader().getResourceAsStream("test20161227/text.txt");System.out.println(is.available());*//*InputStream is = Relation_Absolute.class.getResourceAsStream("/test20161227/text.txt");System.out.println(is.available());*/}

7：

/* * 以  字节流 形式读取properties文件 */public class ReadPropertiesDemo_Stream {public static void main(String[] args) {String path = "test20161227/jdbc.txt";String content = getTxtContentFromPath(path);String[] rows = content.split("[\\u000a\\u000d]");Map<String,String> map = new HashMap<>();for (String row : rows) {if((row!=null && row.trim().length()>0) && !row.trim().startsWith("#")){String[] strs = row.split("=");String key = row.split("=")[0];if(strs.length<2){map.put(key, "");}else{String val = row.split("=")[1];map.put(key, val);}}}for (String key : map.keySet()) {System.out.println(key+":"+map.get(key)); }}private static String getTxtContentFromPath(String path) {InputStream is = ReadPropertiesDemo_Stream.class.getClassLoader().getResourceAsStream(path);BufferedInputStream bis = new BufferedInputStream(is);byte[] bs = new byte[512];StringBuilder strb = new StringBuilder();while(true){try {int count =bis.read(bs);if(count==-1){break;}strb.append(new String(bs,0,count,"UTF-8"));} catch (UnsupportedEncodingException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}return strb.toString();}

/* * 以字符流的形式读属性文件 *  */public class ReadPropertiesDemo_Reader {public static void main(String[] args) {try {String path = "test20161227/jdbc.txt";Map<String, String> map = new HashMap<>();InputStream is = ReadPropertiesDemo_Reader.class.getClassLoader().getResourceAsStream(path);BufferedReader br = new BufferedReader(new InputStreamReader(is, "utf-8"));while(true){String row = br.readLine();if(row==null){break;}if((row!=null&&row.trim().length()>0)&&!row.trim().startsWith("#")){String[] strs = row.split("=");String key = row.split("=")[0];if(strs.length<2){map.put(key, "");}else{String val = row.split("=")[1];map.put(key, val);}}}for (String key : map.keySet()) {System.out.println(key+":"+map.get(key));}} catch (UnsupportedEncodingException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}

8：

/* * 字节流 */public class InputStreamDemo {public static void main(String[] args)  {//找到文件再说！！File file = new File("e://aa.txt");if(file.exists()){InputStream is = null;try {is = new FileInputStream(file);byte[] bs = new byte[512];int countOfRead = -1;while((countOfRead=is.read(bs))!=-1){String str = new String(bs,0,countOfRead,"GBK");System.out.print(str);}} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally{try {if(is!=null){is.close();}} catch (IOException e) {e.printStackTrace();}}}}

/* * 输出流 */public class OutPutStreamDemo {public static void main(String[] args)  {//找到文件再说！！System.out.println("用铲更好用！！");File fileIn = new File("e://aa.txt");File dir = new File("e://images");if(!dir.exists()){dir.mkdir();}File fileOut = new File(dir,123456+".txt");long currentTimeMillis = System.currentTimeMillis();if(fileIn.exists()){InputStream is = null;OutputStream os = null;try {is = new FileInputStream(fileIn);os = new FileOutputStream(fileOut,false);byte[] bs = new byte[1024];int countOfRead = -1;while((countOfRead=is.read(bs))!=-1){os.write(bs, 0, countOfRead);os.flush();}System.out.println(System.currentTimeMillis() - currentTimeMillis);} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally{try {if(is!=null){is.close();}} catch (IOException e) {e.printStackTrace();}try {if(os!=null){os.close();}} catch (IOException e) {e.printStackTrace();}}}}

9：

/* * 基本的字符流读复制文本 */public class copy_print {public static void main(String[] args) throws Exception {File fileIn = new File("e://aa.txt");File fileOut = new File("e://a_gbk.txt");if (fileOut.exists()) {fileOut.delete();}fileOut.createNewFile();//先得到字节流,转换成字符流,这样可以设置编码Reader reader = new InputStreamReader(new FileInputStream(fileIn),"GBK");//new FileReader(fileIn,"GBK");//这个代码是错的，直接读取文本,不能指定编码BufferedReader br = new BufferedReader(reader);BufferedWriter out = new BufferedWriter(new FileWriter(fileOut));while(true){String txt = br.readLine();if(txt==null){break;}out.write(txt+"\r\n");out.flush();System.out.println(txt);}br.close();out.close();}

public static void main(String[] args) throws Exception {File fileIn = new File("e://aa.txt");File fileOut = new File("e://aaaa.txt");if (fileOut.exists()) {fileOut.delete();}fileOut.createNewFile();BufferedReader br = new BufferedReader(new FileReader(fileIn));//BufferedWriter out = new BufferedWriter(new FileWriter(fileOut));PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter(fileOut)));while(true){String txt = br.readLine();if(txt==null){break;}System.out.println(txt);out.println(txt); out.flush();//不能省！}br.close();out.close();}

10：FileReader:不能指定文件编码        inputstreamRedader可以指定编码