- 浏览: 6875926 次
- 性别:
- 来自: 上海
最新评论
-
autosuggestion:
实现一个智能提示功能需要JavaScript、ajax、数据库 ...
自动提示结果 -
岁月之眸:
...
Java读TXT文件 -
yujian58:
写的好。
在线客服技术方案 -
QQ1067184821:
你好,能不能发个完整的给我呢?1067184821@qq.co ...
Extjs3.2+Json lib动态树与GridPanel简单展现 -
chenhua0725:
能不能发一个完成的包给我呢,谢谢了,83667664@qq.c ...
Extjs3.2+Json lib动态树与GridPanel简单展现
20个经典的Java应用
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
2. 向文件末尾添加内容
3. 得到当前方法的名字
4. 转字符串到日期
或者是:
5. 使用JDBC链接Oracle
6. 把 Java util.Date 转成 sql.Date
7. 使用NIO进行快速的文件拷贝
8. 创建图片的缩略图
9. 创建 JSON 格式的数据
10. 使用iText JAR生成PDF
11. HTTP 代理设置
13. 抓屏程序
14. 列出文件和目录
15. 创建ZIP和JAR文件
16. 解析/读取XML 文件
17. 把 Array 转换成 Map
18. 发送邮件
19. 发送代数据的HTTP 请求
20. 改变数组的大小
1. 字符串有整型的相互转换
[java]
- Java代码
- String a = String.valueOf(2); 或者 String a=2+""; //integer to numeric string
- int i = Integer.parseInt(a); //numeric string to an int
[java]
- Java代码
- 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();
- }
- }
[java]
- Java代码
- String methodName = Thread.currentThread().getStackTrace()[1].getMethodName();
[java]
- Java代码
- java.util.Date = java.text.DateFormat.getDateInstance().parse(date String);
[java]
- SimpleDateFormat format = new SimpleDateFormat( "dd.MM.yyyy" );
- Date date = format.parse( myString );
[java]
- Java代码
- 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();
- }
- }
[java]
- Java代码
- java.util.Date utilDate = new java.util.Date();
- java.sql.Date sqlDate = new java.sql.Date(utilDate.getTime());
[java]
- Java代码
- 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();
- }
- }
- }
[java]
- Java代码
- 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();
- }
[java]
- Java代码
- 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();
- ...
[java]
- Java代码
- 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();
- }
- }
- }
[java]
- Java代码
- 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
[java]
- Java代码
- 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();
[java]
- Java代码
- 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));
- }
- ...
- 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));
- }
[java]
- Java代码
- 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() {
- 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);
[java]
- Java代码
- 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 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();
- }
- }
[java]
- Java代码
- XML文件
- <?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
- 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");
- }
- }
[java]
- Java代码
- 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"));
- }
- }
[java]
- Java代码
- 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);
- }
[java]
- Java代码
- 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("http://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();
- }
- }
- }
[java]
- Java代码
- 查看源代码打印帮助
- 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 i=0; i<a.length; i++)
- System.out.println (a[i]);
- }
相关推荐
说明:注册CSDN用户可得20资源分)Java企业级应用开发指南对JAVA 学习是个不错的参考,里面有很多具体实例。
第一个实验:输入10个整数进行排列 第二个实验:复数加减法运算 第三个实验:Java的继承和多态编程,公司员工管理 第四个实验:小型计算器,四则运算。
东北财经大学20春《Java语言应用开发基础》单元作业二(参考答案).docx
实验二 Java 结构化程序设计应用 3 实验三 Java 数组和方法应用 10 实验四 类和对象;类的继承和派生;多态性;接口;构造器应用 16 实验五 Java访问控制管理;封装类;内部类; 内存管理与垃圾收集 8 实验六 Java ...
第三十二,编程题: 写一个Singleton出来。 Singleton模式主要作用是保证在Java应用程序中,一个类Class只有一个实例存在。
java 网络摄像头,可以装在支持java的手机上用 我不懂啊还非要20个字么,
Java Web开发实例大全(提高卷)筛选、汇集了Java Web开发从基础知识到高级应用各个层面的大量实例及源代码,共有600个左右,每个实例及源代码按实例说明、关键技术、设计过程、详尽注释、秘笈心法的顺序进行了分析...
20个Java开源项目源码打包下载,Java 是一种面向对象的编程语言,用于构建移动、桌面、Web 和嵌入式应用程序。
39 实例17 使用工具提示 42 实例18 不同界面的风格 43 第2章 Java的二维和三维图形处理 45 实例19 颜色处理 46 实例20 合成效果 47 实例21 多种字体效果 49 实例22 合成两个图片 53 实例23 ...
Java经典编程源码例程,可以做为你的学习设计参考。 第1章 Java语言概述 1 实例001 输出“Hello World” 2 实例002 输出控制台传递的参数 2 实例003 输出由“*”组成的三角形 3 实例004 输出符号表情 5 第2章 ...
Java 3DMenu 界面源码,有人说用到游戏中不错,其实平时我信编写Java应用程序时候也能用到吧,不一定非要局限于游戏吧,RES、SRC资源都有,都在压缩包内。 Java zip压缩包查看程序源码 1个目标文件 摘要:Java源码...
Java Web开发实例大全(提高卷)筛选、汇集了Java Web开发从基础知识到高级应用各个层面的大量实例及源代码,共有600个左右,每个实例及源代码按实例说明、关键技术、设计过程、详尽注释、秘笈心法的顺序进行了分析...
主要列出一些经典的例子供大家应用,还有JAVA的一些介绍东西供大家参考
伴随着Java的成长,《Java核心技术》从第1版到第11版一路走来,得到了广大Java程序设计人员的青睐,成为一本畅销不衰的Java经典图书。 本书经全面修订,以涵盖Java 17的新特性。新版延续之前版本的优良传统,用数百...
九、 Java的应用 十、 J2DK的下载和操作。 考试方式: 笔试:90分钟,满分100分,其中含公共基础知识部分的30分。 上机操作:90分钟,满分100分。 上机题目类型要求: (1) 基本操作。 (2) 简单应用。 ...
Java 3DMenu 界面源码,有人说用到游戏中不错,其实平时我信编写Java应用程序时候也能用到吧,不一定非要局限于游戏吧,RES、SRC资源都有,都在压缩包内。 Java zip压缩包查看程序源码 1个目标文件 摘要:Java源码...
1.5 运行第一个Java程序 7 1.6 巩固练习 8 第2章 理解对象与类 9 2.1 什么是对象 9 2.2 什么是类 9 2.3 HelloJava示例的分析 11 2.4 巩固练习 12 第3章 Java语言的基本语法 13 3.1 代码编写规则...
收入了164个完整的、来自实战的Java编程实例,每个例子都有详尽的注释,全新的第二版涵盖了Java v1.3,实现了20个不同的Java API,其中包括Servelt、JSP、XML、Swing和Java2D java 网络高级编程(PDF) 介绍了网络...
对于想将Java应用于实际项目中的程序员来说,《Java核心技术——基础知识》修订版是一本权威性的指导书籍。对于Java SE 6平台的全部更新,这本实用的教程和可靠的参考书通过大量测试过的示例说明了最重要的语言特性...