20个非常有用的Java程序片段

来源：互联网发布：电子音乐制作软件水果编辑：程序博客网时间：2024/06/07 07:10

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

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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

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BufferedWriter out =null;  
try {  
    out =new BufferedWriter(newFileWriter(”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

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

　　4. 转字符串到日期

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<span style="width: auto; height: auto; float: none;"id="12_nwp"><a style="text-decoration: none;"mpid="12" target="_blank" href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_id=0&c=news&cf=1001&ch=0&di=128&fv=10&is_app=0&jk=4aaf3ef6388c118e&k=java&k0=java&kdi0=0&luki=3&n=10&p=baidu&q=06011078_cpr&rb=0&rs=1&seller_id=1&sid=8e118c38f63eaf4a&ssp2=1&stid=0&t=tpclicked3_hc&td=1922429&tu=u1922429&u=http%3A%2F%2Fwww%2Eadmin10000%2Ecom%2Fdocument%2F6065%2Ehtml&urlid=0"id="12_nwl"><span style="color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">java</span></a></span>.util.Date = java.text.DateFormat.getDateInstance().parse(date String);

　　或者是：

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

　　5. 使用JDBC链接Oracle

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public class OracleJdbcTest  
{  
    String driverClass ="oracle.jdbc.driver.OracleDriver"; 
 
    Connection con; 
 
    publicvoid 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); 
    } 
 
    publicvoid fetch() throwsSQLException, 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(); 
    } 
 
    publicstatic void main(String[] args)  
    { 
        OracleJdbcTest test =new OracleJdbcTest(); 
        test.init(); 
        test.fetch(); 
    } 
}

　　6. 把 Java util.Date 转成 sql.Date

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<span style="width: auto; height: auto; float: none;"id="11_nwp"><a style="text-decoration: none;"mpid="11" target="_blank" href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_id=0&c=news&cf=1001&ch=0&di=128&fv=10&is_app=0&jk=4aaf3ef6388c118e&k=java&k0=java&kdi0=0&luki=3&n=10&p=baidu&q=06011078_cpr&rb=0&rs=1&seller_id=1&sid=8e118c38f63eaf4a&ssp2=1&stid=0&t=tpclicked3_hc&td=1922429&tu=u1922429&u=http%3A%2F%2Fwww%2Eadmin10000%2Ecom%2Fdocument%2F6065%2Ehtml&urlid=0"id="11_nwl"><span style="color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">java</span></a></span>.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

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public static void fileCopy( File in, File out ) 
            throwsIOException  
    { 
        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) 
            intmaxCount = (64 * 1024 * 1024) - (32* 1024); 
            longsize = inChannel.size();  
            longposition = 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

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private void createThumbnail(String filename, intthumbWidth, intthumbHeight, intquality, String outFilename)  
        throwsInterruptedException, FileNotFoundException, IOException 
    { 
        // load image from filename 
        Image image = Toolkit.getDefaultToolkit().getImage(filename); 
        MediaTracker mediaTracker =new MediaTracker(newContainer());  
        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 
        <span style="width: auto; height: auto; float: none;"id="10_nwp"><a style="text-decoration: none;"mpid="10" target="_blank" href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_id=0&c=news&cf=1001&ch=0&di=128&fv=10&is_app=0&jk=4aaf3ef6388c118e&k=double&k0=double&kdi0=0&luki=2&n=10&p=baidu&q=06011078_cpr&rb=0&rs=1&seller_id=1&sid=8e118c38f63eaf4a&ssp2=1&stid=0&t=tpclicked3_hc&td=1922429&tu=u1922429&u=http%3A%2F%2Fwww%2Eadmin10000%2Ecom%2Fdocument%2F6065%2Ehtml&urlid=0"id="10_nwl"><span style="color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">double</span></a></span> thumbRatio = (double)thumbWidth / (double)thumbHeight; 
        intimageWidth = image.getWidth(null); 
        intimageHeight = image.getHeight(null); 
        doubleimageRatio = (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(newFileOutputStream(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)

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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

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import <span style="width: auto; height: auto; float: none;"id="9_nwp"><a style="text-decoration: none;"mpid="9" target="_blank" href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_id=0&c=news&cf=1001&ch=0&di=128&fv=10&is_app=0&jk=4aaf3ef6388c118e&k=java&k0=java&kdi0=0&luki=3&n=10&p=baidu&q=06011078_cpr&rb=0&rs=1&seller_id=1&sid=8e118c38f63eaf4a&ssp2=1&stid=0&t=tpclicked3_hc&td=1922429&tu=u1922429&u=http%3A%2F%2Fwww%2Eadmin10000%2Ecom%2Fdocument%2F6065%2Ehtml&urlid=0"id="9_nwl"><span style="color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">java</span></a></span>.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 {  
 
    publicstatic void main(String[] args) {  
        try{  
            OutputStream file =new FileOutputStream(newFile("C:\\Test.pdf")); 
 
            Document document =new Document(); 
            PdfWriter.getInstance(document, file); 
            document.open(); 
            document.add(newParagraph("Hello Kiran")); 
            document.add(newParagraph(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。

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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

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public class SimpleSingleton {  
    privatestatic SimpleSingleton singleInstance = new SimpleSingleton(); 
 
    //Marking default constructor private 
    //to avoid direct instantiation. 
    privateSimpleSingleton() {  
    } 
 
    //Get instance for class SimpleSingleton 
    publicstatic SimpleSingleton getInstance() { 
 
        returnsingleInstance;  
    } 
}

　　另一种实现

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public enum SimpleSingleton {  
    INSTANCE; 
    publicvoid 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。

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import <span style="width: auto; height: auto; float: none;"id="8_nwp"><a style="text-decoration: none;"mpid="8" target="_blank" href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_id=0&c=news&cf=1001&ch=0&di=128&fv=10&is_app=0&jk=4aaf3ef6388c118e&k=java&k0=java&kdi0=0&luki=3&n=10&p=baidu&q=06011078_cpr&rb=0&rs=1&seller_id=1&sid=8e118c38f63eaf4a&ssp2=1&stid=0&t=tpclicked3_hc&td=1922429&tu=u1922429&u=http%3A%2F%2Fwww%2Eadmin10000%2Ecom%2Fdocument%2F6065%2Ehtml&urlid=0"id="8_nwl"><span style="color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">java</span></a></span>.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) throwsException {  
 
   Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize(); 
   Rectangle screenRectangle =new Rectangle(screenSize); 
   Robot robot =new Robot();  
   BufferedImage image = robot.createScreenCapture(screenRectangle); 
   ImageIO.write(image,"png", newFile(fileName));  
 
}  
...

　　14. 列出文件和目录

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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 i=0; 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() { 
      publicboolean 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() { 
      publicboolean accept(File file) { 
          returnfile.isDirectory();  
      } 
  }; 
  files = dir.listFiles(fileFilter);

　　15. 创建ZIP和JAR文件

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import <span style="width: auto; height: auto; float: none;"id="7_nwp"><a style="text-decoration: none;"mpid="7" target="_blank" href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_id=0&c=news&cf=1001&ch=0&di=128&fv=10&is_app=0&jk=4aaf3ef6388c118e&k=java&k0=java&kdi0=0&luki=3&n=10&p=baidu&q=06011078_cpr&rb=0&rs=1&seller_id=1&sid=8e118c38f63eaf4a&ssp2=1&stid=0&t=tpclicked3_hc&td=1922429&tu=u1922429&u=http%3A%2F%2Fwww%2Eadmin10000%2Ecom%2Fdocument%2F6065%2Ehtml&urlid=0"id="7_nwl"><span style="color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">java</span></a></span>.util.zip.*; 
import java.io.*;  
 
public class ZipIt {  
    publicstatic 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); 
        intbytesRead;  
        byte[] buffer =new byte[1024]; 
        CRC32 crc =new CRC32();  
        for(int i=1, n=args.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( 
                newFileInputStream(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( 
                newFileInputStream(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

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<?xml version="1.0"?>
<students> 
    <student>
        <name>John</name>
        <grade>B</grade>
        <age>12</age>
    </student>
    <student>
        <name>Mary</name>
        <grade>A</grade>
        <age>11</age>
    </student>
    <student>
        <name>Simon</name>
        <grade>A</grade>
        <age>18</age>
    </student>
</students>

　　Java代码

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package net.viralpatel.<span style="width: auto; height: auto; float: none;"id="4_nwp"><a style="text-decoration: none;"mpid="4" target="_blank" href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_id=0&c=news&cf=1001&ch=0&di=128&fv=10&is_app=0&jk=4aaf3ef6388c118e&k=java&k0=java&kdi0=0&luki=3&n=10&p=baidu&q=06011078_cpr&rb=0&rs=1&seller_id=1&sid=8e118c38f63eaf4a&ssp2=1&stid=0&t=tpclicked3_hc&td=1922429&tu=u1922429&u=http%3A%2F%2Fwww%2Eadmin10000%2Ecom%2Fdocument%2F6065%2Ehtml&urlid=0"id="4_nwl"><span style="color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">java</span></a></span>.<span style="width: auto; height: auto; float: none;"id="5_nwp"><a style="text-decoration: none;"mpid="5" target="_blank" href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_id=0&c=news&cf=1001&ch=0&di=128&fv=10&is_app=0&jk=4aaf3ef6388c118e&k=xml&k0=xml&kdi0=0&luki=1&n=10&p=baidu&q=06011078_cpr&rb=0&rs=1&seller_id=1&sid=8e118c38f63eaf4a&ssp2=1&stid=0&t=tpclicked3_hc&td=1922429&tu=u1922429&u=http%3A%2F%2Fwww%2Eadmin10000%2Ecom%2Fdocument%2F6065%2Ehtml&urlid=0"id="5_nwl"><span style="color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">xml</span></a></span>parser; 
 
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 {  
 
    publicvoid 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); 
        } 
    } 
    publicstatic void main(String[] args) {  
 
        XMLParser parser =new XMLParser(); 
        parser.getAllUserNames("c:\\test.<span style="width: auto; height: auto;float: none;" id="6_nwp"><a style="text-decoration: none;" mpid="6" target="_blank" href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_id=0&c=news&cf=1001&ch=0&di=128&fv=10&is_app=0&jk=4aaf3ef6388c118e&k=xml&k0=xml&kdi0=0&luki=1&n=10&p=baidu&q=06011078_cpr&rb=0&rs=1&seller_id=1&sid=8e118c38f63eaf4a&ssp2=1&stid=0&t=tpclicked3_hc&td=1922429&tu=u1922429&u=http%3A%2F%2Fwww%2Eadmin10000%2Ecom%2Fdocument%2F6065%2Ehtml&urlid=0" id="6_nwl"><span style="color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">xml</span></a></span>"); 
    } 
}

　　17. 把 Array 转换成 Map

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import <span style="width: auto; height: auto; float: none;"id="3_nwp"><a style="text-decoration: none;"mpid="3" target="_blank" href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_id=0&c=news&cf=1001&ch=0&di=128&fv=10&is_app=0&jk=4aaf3ef6388c118e&k=java&k0=java&kdi0=0&luki=3&n=10&p=baidu&q=06011078_cpr&rb=0&rs=1&seller_id=1&sid=8e118c38f63eaf4a&ssp2=1&stid=0&t=tpclicked3_hc&td=1922429&tu=u1922429&u=http%3A%2F%2Fwww%2Eadmin10000%2Ecom%2Fdocument%2F6065%2Ehtml&urlid=0"id="3_nwl"><span style="color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">java</span></a></span>.util.Map; 
import org.apache.commons.lang.ArrayUtils;  
 
public class Main {  
 
  publicstatic 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

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import <span style="width: auto; height: auto; float: none;"id="2_nwp"><a style="text-decoration: none;"mpid="2" target="_blank" href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_id=0&c=news&cf=1001&ch=0&di=128&fv=10&is_app=0&jk=4aaf3ef6388c118e&k=java&k0=java&kdi0=0&luki=3&n=10&p=baidu&q=06011078_cpr&rb=0&rs=1&seller_id=1&sid=8e118c38f63eaf4a&ssp2=1&stid=0&t=tpclicked3_hc&td=1922429&tu=u1922429&u=http%3A%2F%2Fwww%2Eadmin10000%2Ecom%2Fdocument%2F6065%2Ehtml&urlid=0"id="2_nwl"><span style="color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">java</span></a></span>x.mail.*; 
import javax.mail.internet.*;  
import java.util.*;  
 
public void postMail( String recipients[ ], String subject, String message , String from)throws MessagingException 
{  
    booleandebug = 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

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import <span style="width: auto; height: auto; float: none;"id="1_nwp"><a style="text-decoration: none;"mpid="1" target="_blank" href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_id=0&c=news&cf=1001&ch=0&di=128&fv=10&is_app=0&jk=4aaf3ef6388c118e&k=java&k0=java&kdi0=0&luki=3&n=10&p=baidu&q=06011078_cpr&rb=0&rs=1&seller_id=1&sid=8e118c38f63eaf4a&ssp2=1&stid=0&t=tpclicked3_hc&td=1922429&tu=u1922429&u=http%3A%2F%2Fwww%2Eadmin10000%2Ecom%2Fdocument%2F6065%2Ehtml&urlid=0"id="1_nwl"><span style="color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">java</span></a></span>.io.BufferedReader; 
import java.io.InputStreamReader;  
import java.net.URL;  
 
public class Main {  
    publicstatic void main(String[] args)  {  
        try{  
            URL my_url =new URL("http://coolshell.cn/"); 
            BufferedReader br =new BufferedReader(newInputStreamReader(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

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/** 
* 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) {  
   intoldSize = <span style="width: auto; height: auto; float: none;"id="0_nwp"><a style="text-decoration: none;"mpid="0" target="_blank" href="http://cpro.baidu.com/cpro/ui/uijs.php?adclass=0&app_id=0&c=news&cf=1001&ch=0&di=128&fv=10&is_app=0&jk=4aaf3ef6388c118e&k=java&k0=java&kdi0=0&luki=3&n=10&p=baidu&q=06011078_cpr&rb=0&rs=1&seller_id=1&sid=8e118c38f63eaf4a&ssp2=1&stid=0&t=tpclicked3_hc&td=1922429&tu=u1922429&u=http%3A%2F%2Fwww%2Eadmin10000%2Ecom%2Fdocument%2F6065%2Ehtml&urlid=0"id="0_nwl"><span style="color:#0000ff;font-size:14px;width:auto;height:auto;float:none;">java</span></a></span>.lang.reflect.Array.getLength(oldArray); 
   Class elementType = oldArray.getClass().getComponentType(); 
   Object newArray = java.lang.reflect.Array.newInstance( 
         elementType,newSize); 
   intpreserveLength = Math.min(oldSize,newSize);  
   if(preserveLength > 0) 
      System.arraycopy (oldArray,0,newArray,0,preserveLength); 
   returnnewArray;  
}  
 
// 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 i=0; i<a.length; i++) 
      System.out.println (a[i]); 
}

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