分享非常有用的Java程序 (关键代码) (一)

 分享一些非常有用的Java程序 (关键代码) ,希望对你有所帮助。

1.  得到当前方法的名字

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

2. 转字符串到日期

java.util.Date = java.text.DateFormat.getDateInstance().parse(date String); 

或者是：

SimpleDateFormat format = new SimpleDateFormat( "dd.MM.yyyy" ); Date date = format.parse( myString ); 

3.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();       }   

4.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()); 

5.创建图片的缩略图

private void createThumbnail(String filename, int thumbWidth, int thumbHeight, int quality, String outFilename)           throws InterruptedException, FileNotFoundException, IOException       {           // load image from filename           Image image = Toolkit.getDefaultToolkit().getImage(filename);           MediaTracker mediaTracker = new MediaTracker(new Container());           mediaTracker.addImage(image, 0);           mediaTracker.waitForID(0);           // use this to test for errors at this point: System.out.println(mediaTracker.isErrorAny());              // determine thumbnail size from WIDTH and HEIGHT           double thumbRatio = (double)thumbWidth / (double)thumbHeight;           int imageWidth = image.getWidth(null);           int imageHeight = image.getHeight(null);           double imageRatio = (double)imageWidth / (double)imageHeight;           if (thumbRatio < imageRatio) {               thumbHeight = (int)(thumbWidth / imageRatio);           } else {               thumbWidth = (int)(thumbHeight * imageRatio);           }              // draw original image to thumbnail image object and           // scale it to the new size on-the-fly           BufferedImage thumbImage = new BufferedImage(thumbWidth, thumbHeight, BufferedImage.TYPE_INT_RGB);           Graphics2D graphics2D = thumbImage.createGraphics();           graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);           graphics2D.drawImage(image, 0, 0, thumbWidth, thumbHeight, null);              // save thumbnail image to outFilename           BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(outFilename));           JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(out);           JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParam(thumbImage);           quality = Math.max(0, Math.min(quality, 100));           param.setQuality((float)quality / 100.0f, false);           encoder.setJPEGEncodeParam(param);           encoder.encode(thumbImage);           out.close();   

6.使用iText JAR生成PDF

import java.io.File; 
import java.io.FileOutputStream; 
import java.io.OutputStream; 
import java.util.Date; 
import com.lowagie.text.Document; 
import com.lowagie.text.Paragraph; 
import com.lowagie.text.pdf.PdfWriter; 
public class GeneratePDF { 
public static void main(String[] args) { 
try { 
OutputStream file = new FileOutputStream(new File("C:\\Test.pdf")); 
Document document = new Document(); 
PdfWriter.getInstance(document, file); 
document.open(); 
document.add(new Paragraph("Hello Kiran")); 
document.add(new Paragraph(new Date().toString())); 
document.close(); 
file.close(); 
} catch (Exception e) { 
e.printStackTrace(); 
} 
} 
}