常用的Java基本代码汇总

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();
        }