常用的Java基本代碼匯總

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1.字串和整型的相互轉換

　　　　　　　　　String a= String.valueOf(2);　　　　　　　　　int i = Integer.parseInt(a);

 2. 向檔案末尾新增內容

　　　　　　　　　BufferedWriter out=null;try {out=new BufferedWriter(new FileWriter("filename",true));out.write("i am stringbuffer!");} catch (IOException e) {e.printStackTrace();}

 3. 得到當前方法的名字

String methodName = Thread.currentThread().getStackTrace()[1].getMethodName();

 4. 轉字串到日期與日期到字串

 //日期到字串 SimpleDateFormat sdf = new SimpleDateFormat( "yyyy年MM月dd日 ");     String str = sdf.format(new Date());     System.out.println(str);     //字串到日期     Date date = sdf.parse(str);     System.out.println(date);

 5. 使用JDBC連結Oracle

public class OracleJdbcTest {String driverClass = "oracle.jdbc.driver.OracleDriver";      Connection con;      public void init(FileInputStream fs)     throws ClassNotFoundException, SQLException, FileNotFoundException, IOException {          Properties props = new Properties();          props.load(fs);          String url = props.getProperty("db.url");          String userName = props.getProperty("db.user");          String password = props.getProperty("db.password");          Class.forName(driverClass);          con=DriverManager.getConnection(url, userName, password);      }        public void fetch() throws SQLException, IOException{          PreparedStatement ps = con.prepareStatement("select SYSDATE from dual");          ResultSet rs = ps.executeQuery();            while (rs.next()){              // do the thing you do          }          rs.close();          ps.close();      }        public static void main(String[] args){          OracleJdbcTest test = new OracleJdbcTest();          test.init();          test.fetch();      } }

 6. 把 Java util.Date 轉成 sql.Date

java.util.Date utilDate = new java.util.Date();  java.sql.Date sqlDate = new java.sql.Date(utilDate.getTime());

 7. 使用NIO進行快速的檔案拷貝

public static void fileCopy( File in, File out )              throws IOException  {          FileChannel inChannel = new FileInputStream( in ).getChannel();          FileChannel outChannel = new FileOutputStream( out ).getChannel();          try{          // inChannel.transferTo(0, inChannel.size(), outChannel);          // original -- apparently has trouble copying large files on Windows              // magic number for Windows, 64Mb - 32Kb)              int maxCount = (64 * 1024 * 1024) - (32 * 1024);              long size = inChannel.size();              long position = 0;              while ( position < size ){                 position += inChannel.transferTo(position, maxCount, outChannel );              }          }finally{              if (inChannel != null){                 inChannel.close();              }              if (outChannel != null){                  outChannel.close();              }          }      }

 8. 列出檔案和目錄

import java.io.File;import java.io.FileFilter;import java.io.FilenameFilter;public class Test {public static void main(String[] args) {  File dir = new File("F:\\韓順平java");    String[] children = dir.list();   if (children == null) {        // Either dir does not exist or is not a directory    } else {        for (int i=0; i < children.length; i++) {            // Get filename of file or directory            String filename = children[i];            System.out.println(i+"   ---"+filename);      }    }    // It is also possible to filter the list of returned files.    // This example does not return any files that start with ‘.‘.    FilenameFilter filter = new FilenameFilter() {        public boolean accept(File dir, String name) {            return !name.startsWith(".");        }    };    children = dir.list(filter);    // The list of files can also be retrieved as File objects    File[] files = dir.listFiles();      // This filter only returns directories    FileFilter fileFilter = new FileFilter() {        public boolean accept(File file) {            return file.isDirectory();        }    };    files = dir.listFiles(fileFilter);} }

9. 發送代資料的HTTP 要求

try {              URL my_url = new URL("連結地址");              BufferedReader br = new BufferedReader(new InputStreamReader(my_url.openStream()));              String strTemp = "";              while(null != (strTemp = br.readLine())){              System.out.println(strTemp);          }          } catch (Exception ex) {              ex.printStackTrace();          } 

　　

 

常用的Java基本代碼匯總