常用的Java代码段有哪些

String a = String.valueOf2);   //integer to numeric string  
int i = Integer.parseInta); //numeric string to an int

BufferedWriter out = null;  
try {  
    out = new BufferedWriternew FileWriter”filename”, true));  
    out.write”aString”);  
} catch IOException e) {  
    // error processing code  
} finally {  
    if out != null) {  
        out.close);  
    }  
}

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

java.util.Date = java.text.DateFormat.getDateInstance).parsedate String);

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

public class OracleJdbcTest  
{  
    String driverClass = "oracle.jdbc.driver.OracleDriver";  
 
    Connection con;  
 
    public void initFileInputStream fs) throws ClassNotFoundException, SQLException, FileNotFoundException, IOException  
    {  
        Properties props = new Properties);  
        props.loadfs);  
        String url = props.getProperty"db.url");  
        String userName = props.getProperty"db.user");  
        String password = props.getProperty"db.password");  
        Class.forNamedriverClass);  
 
        con=DriverManager.getConnectionurl, 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 mainString[] args)  
    {  
        OracleJdbcTest test = new OracleJdbcTest);  
        test.init);  
        test.fetch);  
    }  
}

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

public static void fileCopy File in, File out )  
            throws IOException  
    {  
        FileChannel inChannel = new FileInputStream in ).getChannel);  
        FileChannel outChannel = new FileOutputStream out ).getChannel);  
        try
        {  
//          inChannel.transferTo0, 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);  
            }  
        }  
    }

private void createThumbnailString filename, int thumbWidth, int thumbHeight, int quality, String outFilename)  
        throws InterruptedException, FileNotFoundException, IOException  
    {  
        // load image from filename  
        Image image = Toolkit.getDefaultToolkit).getImagefilename);  
        MediaTracker mediaTracker = new MediaTrackernew Container));  
        mediaTracker.addImageimage, 0);  
        mediaTracker.waitForID0);  
        // use this to test for errors at this point: System.out.printlnmediaTracker.isErrorAny));  
 
        // determine thumbnail size from WIDTH and HEIGHT  
        double thumbRatio = double)thumbWidth / double)thumbHeight;  
        int imageWidth = image.getWidthnull);  
        int imageHeight = image.getHeightnull);  
        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 BufferedImagethumbWidth, thumbHeight, BufferedImage.TYPE_INT_RGB);  
        Graphics2D graphics2D = thumbImage.createGraphics);  
        graphics2D.setRenderingHintRenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR);  
        graphics2D.drawImageimage, 0, 0, thumbWidth, thumbHeight, null);  
 
        // save thumbnail image to outFilename  
        BufferedOutputStream out = new BufferedOutputStreamnew FileOutputStreamoutFilename));  
        JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoderout);  
        JPEGEncodeParam param = encoder.getDefaultJPEGEncodeParamthumbImage);  
        quality = Math.max0, Math.minquality, 100));  
        param.setQualityfloat)quality / 100.0f, false);  
        encoder.setJPEGEncodeParamparam);  
        encoder.encodethumbImage);  
        out.close);  
    }

import org.json.JSONObject;  
...  
...  
JSONObject json = new JSONObject);  
json.put"city", "Mumbai");  
json.put"country", "India");  
...  
String output = json.toString);  
...

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 mainString[] args) {  
        try {  
            OutputStream file = new FileOutputStreamnew File"C:\\Test.pdf"));  
 
            Document document = new Document);  
            PdfWriter.getInstancedocument, file);  
            document.open);  
            document.addnew Paragraph"Hello Kiran"));  
            document.addnew Paragraphnew Date).toString)));  
 
            document.close);  
            file.close);  
 
        } catch Exception e) {  
 
            e.printStackTrace);  
        }  
    }  
}