java代码段有哪些 常用的Java代码段有哪些

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String a = String.valueOf(2); //integer to numeric string

int i = Integer.parseInt(a); //numeric string to an int

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BufferedWriter out = null;

try {

out = new BufferedWriter(new FileWriter(”filename”, true));

out.write(”aString”);

} catch (IOException e) {

// error processing code

} finally {

if (out != null) {

out.close();

}

}

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

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

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SimpleDateFormat format = new SimpleDateFormat( "dd.MM.yyyy" );

Date date = format.parse( myString );

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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();

}

}

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java.util.Date utilDate = new java.util.Date();

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

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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();

}

}

}

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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();

}

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import org.json.JSONObject;

...

...

JSONObject json = new JSONObject();

json.put("city", "Mumbai");

json.put("country", "India");

...

String output = json.toString();

...

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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();

}

}

}