1.字符串和整型的相互转换
String a= String.valueOf(2); int i = Integer.parseInt(a);
2. 向文件末尾添加内容
BufferedWriter out=null; try { out=new BufferedWriter(new FileWriter("filename",true)); out.write("i am stringbuffer!"); } catch (IOException e) { e.printStackTrace(); }
3. 得到当前方法的名字
String methodName = Thread.currentThread().getStackTrace()[1].getMethodName();
4. 转字符串到日期与日期到字符串
//日期到字符串 SimpleDateFormat sdf = new SimpleDateFormat( "yyyy年MM月dd日 "); String str = sdf.format(new Date()); System.out.println(str); //字符串到日期 Date date = sdf.parse(str); System.out.println(date);
5. 使用JDBC链接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 转成 sql.Date
java.util.Date utilDate = new java.util.Date(); java.sql.Date sqlDate = new java.sql.Date(utilDate.getTime());
7. 使用NIO进行快速的文件拷贝
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. 列出文件和目录
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:\韩顺平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. 发送代数据的HTTP 请求
try { URL my_url = new URL("链接地址"); 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(); }