如何查网站是织梦做的,个人适合网站类型,wordpress 站内搜索代码,seo如何分析网站转载自 20个非常有用的Java程序片段下面是20个非常有用的Java程序片段#xff0c;希望能对你有用。
1. 字符串有整型的相互转换String a String.valueOf(2); //integer to numeric string
int i Integer.parseInt(a); //numeric string to an int 2. 向文件末尾添加内…转载自 20个非常有用的Java程序片段下面是20个非常有用的Java程序片段希望能对你有用。
1. 字符串有整型的相互转换String a String.valueOf(2); //integer to numeric string
int i Integer.parseInt(a); //numeric string to an int
2. 向文件末尾添加内容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(); }
} 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 ); 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); conDriverManager.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. 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(); } 9. 创建 JSON 格式的数据
请先阅读这篇文章 了解一些细节并下面这个JAR 文件json-rpc-1.0.jar (75 kb)
import org.json.JSONObject;
...
...
JSONObject json new JSONObject();
json.put(city, Mumbai);
json.put(country, India);
...
String output json.toString();
... 10. 使用iText JAR生成PDF
阅读这篇文章 了解更多细节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(); } }
} 11. HTTP 代理设置
阅读这篇 文章 了解更多细节。System.getProperties().put(http.proxyHost, someProxyURL);
System.getProperties().put(http.proxyPort, someProxyPort);
System.getProperties().put(http.proxyUser, someUserName);
System.getProperties().put(http.proxyPassword, somePassword); 12. 单实例Singleton 示例
请先阅读这篇文章 了解更多信息public class SimpleSingleton { private static SimpleSingleton singleInstance new SimpleSingleton(); //Marking default constructor private //to avoid direct instantiation. private SimpleSingleton() { } //Get instance for class SimpleSingleton public static SimpleSingleton getInstance() { return singleInstance; }
} 另一种实现
public enum SimpleSingleton { INSTANCE; public void doSomething() { }
} //Call the method from Singleton:
SimpleSingleton.INSTANCE.doSomething(); 13. 抓屏程序
阅读这篇文章 获得更多信息。
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.Robot;
import java.awt.Toolkit;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import java.io.File; ... public void captureScreen(String fileName) throws Exception { Dimension screenSize Toolkit.getDefaultToolkit().getScreenSize(); Rectangle screenRectangle new Rectangle(screenSize); Robot robot new Robot(); BufferedImage image robot.createScreenCapture(screenRectangle); ImageIO.write(image, png, new File(fileName)); }
... 14. 列出文件和目录
File dir new File(directoryName); String[] children dir.list(); if (children null) { // Either dir does not exist or is not a directory } else { for (int i0; i children.length; i) { // Get filename of file or directory String filename children[i]; } } // 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); 15. 创建ZIP和JAR文件import java.util.zip.*;
import java.io.*; public class ZipIt { public static void main(String args[]) throws IOException { if (args.length 2) { System.err.println(usage: java ZipIt Zip.zip file1 file2 file3); System.exit(-1); } File zipFile new File(args[0]); if (zipFile.exists()) { System.err.println(Zip file already exists, please try another); System.exit(-2); } FileOutputStream fos new FileOutputStream(zipFile); ZipOutputStream zos new ZipOutputStream(fos); int bytesRead; byte[] buffer new byte[1024]; CRC32 crc new CRC32(); for (int i1, nargs.length; i n; i) { String name args[i]; File file new File(name); if (!file.exists()) { System.err.println(Skipping: name); continue; } BufferedInputStream bis new BufferedInputStream( new FileInputStream(file)); crc.reset(); while ((bytesRead bis.read(buffer)) ! -1) { crc.update(buffer, 0, bytesRead); } bis.close(); // Reset to beginning of input stream bis new BufferedInputStream( new FileInputStream(file)); ZipEntry entry new ZipEntry(name); entry.setMethod(ZipEntry.STORED); entry.setCompressedSize(file.length()); entry.setSize(file.length()); entry.setCrc(crc.getValue()); zos.putNextEntry(entry); while ((bytesRead bis.read(buffer)) ! -1) { zos.write(buffer, 0, bytesRead); } bis.close(); } zos.close(); }
} 16. 解析/读取XML 文件
XML文件
?xml version1.0?
students student nameJohn/name gradeB/grade age12/age /student student nameMary/name gradeA/grade age11/age /student student nameSimon/name gradeA/grade age18/age /student
/students Java代码package net.viralpatel.java.xmlparser; import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory; import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList; public class XMLParser { public void getAllUserNames(String fileName) { try { DocumentBuilderFactory dbf DocumentBuilderFactory.newInstance(); DocumentBuilder db dbf.newDocumentBuilder(); File file new File(fileName); if (file.exists()) { Document doc db.parse(file); Element docEle doc.getDocumentElement(); // Print root element of the document System.out.println(Root element of the document: docEle.getNodeName()); NodeList studentList docEle.getElementsByTagName(student); // Print total student elements in document System.out .println(Total students: studentList.getLength()); if (studentList ! null studentList.getLength() 0) { for (int i 0; i studentList.getLength(); i) { Node node studentList.item(i); if (node.getNodeType() Node.ELEMENT_NODE) { System.out .println(); Element e (Element) node; NodeList nodeList e.getElementsByTagName(name); System.out.println(Name: nodeList.item(0).getChildNodes().item(0) .getNodeValue()); nodeList e.getElementsByTagName(grade); System.out.println(Grade: nodeList.item(0).getChildNodes().item(0) .getNodeValue()); nodeList e.getElementsByTagName(age); System.out.println(Age: nodeList.item(0).getChildNodes().item(0) .getNodeValue()); } } } else { System.exit(1); } } } catch (Exception e) { System.out.println(e); } } public static void main(String[] args) { XMLParser parser new XMLParser(); parser.getAllUserNames(c:\\test.xml); }
} 17. 把 Array 转换成 Map import java.util.Map;
import org.apache.commons.lang.ArrayUtils; public class Main { public static void main(String[] args) { String[][] countries { { United States, New York }, { United Kingdom, London }, { Netherland, Amsterdam }, { Japan, Tokyo }, { France, Paris } }; Map countryCapitals ArrayUtils.toMap(countries); System.out.println(Capital of Japan is countryCapitals.get(Japan)); System.out.println(Capital of France is countryCapitals.get(France)); }
} 18. 发送邮件
import javax.mail.*;
import javax.mail.internet.*;
import java.util.*; public void postMail( String recipients[ ], String subject, String message , String from) throws MessagingException
{ boolean debug false; //Set the host smtp address Properties props new Properties(); props.put(mail.smtp.host, smtp.example.com); // create some properties and get the default Session Session session Session.getDefaultInstance(props, null); session.setDebug(debug); // create a message Message msg new MimeMessage(session); // set the from and to address InternetAddress addressFrom new InternetAddress(from); msg.setFrom(addressFrom); InternetAddress[] addressTo new InternetAddress[recipients.length]; for (int i 0; i recipients.length; i) { addressTo[i] new InternetAddress(recipients[i]); } msg.setRecipients(Message.RecipientType.TO, addressTo); // Optional : You can also set your custom headers in the Email if you Want msg.addHeader(MyHeaderName, myHeaderValue); // Setting the Subject and Content Type msg.setSubject(subject); msg.setContent(message, text/plain); Transport.send(msg);
} 19. 发送代数据的HTTP 请求import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL; public class Main { public static void main(String[] args) { try { URL my_url new URL(https://coolshell.cn/); 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(); } }
}20. 改变数组的大小/**
* Reallocates an array with a new size, and copies the contents
* of the old array to the new array.
* param oldArray the old array, to be reallocated.
* param newSize the new array size.
* return A new array with the same contents.
*/
private static Object resizeArray (Object oldArray, int newSize) { int oldSize java.lang.reflect.Array.getLength(oldArray); Class elementType oldArray.getClass().getComponentType(); Object newArray java.lang.reflect.Array.newInstance( elementType,newSize); int preserveLength Math.min(oldSize,newSize); if (preserveLength 0) System.arraycopy (oldArray,0,newArray,0,preserveLength); return newArray;
} // Test routine for resizeArray().
public static void main (String[] args) { int[] a {1,2,3}; a (int[])resizeArray(a,5); a[3] 4; a[4] 5; for (int i0; ia.length; i) System.out.println (a[i]);
}
