工作中总结的一些比较有用的JAVA代码，并送一些积分
（1）把Strings转换成int和把int转换成StringString a = String.valueOf(2);
//integer to numeric string
int i = Integer.parseInt(a); //numeric string to an int
String a = String.valueOf(2);
//integer to numeric string
int i = Integer.parseInt(a); //numeric string to anint
（2）向Java文件中添加文本
public void addFile() {
//Updated: Thanks Simone for pointing to exception. I have changed the code.
BufferedWriter out = null;
try
{
out = new BufferedWriter(new FileWriter("filename", true));
out.write("aString");
} catch (IOException e) {
// error processing code } finally
{
if (out != null) {
try {
out.close();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
}
}
}
}
（3）获取Java现在正调用的方法名
String methodName =
Thread.currentThread().getStackTrace()[1].getMethodName();
String methodName = Thread.currentThread().getStackTrace()[1].getMethodName();
（4）在Java中将String型转换成Date型
java.util.Date =
java.text.DateFormat.getDateInstance().parse(date String); java.util.Date = java.text.DateFormat.getDateInstance().parse(date
String);or SimpleDateFormat format = new SimpleDateFormat( "dd.MM.yyyy"
); Date date = format.parse( myString ); SimpleDateFormat format = new SimpleDateFormat( "dd.MM.yyyy" );Date date
= format.parse( myString );
（5）6.将Java中的util.Date转换成sql.Date
java.util.Date utilDate = new
java.util.Date(); java.sql.Date sqlDate = new java.sql.Date
(utilDate.getTime()); java.util.Date utilDate = new java.util.Date();java.sql.Date sqlDate =
new java.sql.Date(utilDate.getTime());
（6）使用NIO快速复制Java文件
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();
}
}
}
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();}
}}
(7)在Java中创建缩略图
private void createThumbnail1(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();
}
(8)在Java中创建JSON数据
Read this article for more details.Download JAR file 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();
...
import org.json.JSONObject;......JSON
Object json = new JSONObject();
json.put("city", "Mumbai");
json.put("country", "India");
...String
output = json.toString();...
(9) 在Java中使用iText JAR打开PDF
Read this article for more details.
import
import
import
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(); }
} }
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("HelloKiran"));
document.add(new Paragraph(new Date().toString()));
document.close();
file.close();
} catch (Exception e) {
e.printStackTrace();}
}}
(10)在Java上的HTTP代理设置
System.getProperties().put("http.proxyHost", "someProxyURL");
System.getProperties().put("http.proxyPort","someProxyPort");
System.getProperties().put("http.proxyUser", "someUserName");
System.getProperties().put("http.proxyPassword", "somePassword");
System.getProperties().put("http.proxyHost","someProxyURL");
System.getProperties().put("http.proxyPort", "someProxyPort");
System.getProperties().put("http.proxyUser","someUserName");
System.getProperties().put("http.proxyPassword","somePassword");
(11)在Java上做屏幕截图
Read this article for more details.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 ... 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)); }
...
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
...
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));
}...
(12)在Java中创建ZIP和JAR文件
package itf;
import java.util.zip.*;
import *;
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 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(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(); }
}
(13)在Java中解析/读取XML文件
view plaincopy to clipboardprint?<?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>
<?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>S
imon</name><grade>A</grade><age>18</age></student></students>Java code to parse above XML.
view plaincopy to clipboardprint?
package itf;
import
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 documentSystem.out.println("Root
// element of the document: "+ docEle.getNodeName());
NodeList studentList = docEle.getElementsByTagName("student");
// Print total student elements in
// documentSystem.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");
}
}
(14)在Java中将Array转换成Map
package itf;
import java.util.Map;
import org.
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"));
}
}
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