1.字符串-整型相互转换
String s = String.valueOf(2); int a = Integer.parseInt(s);
2.向文件末尾添加内容
BufferedWriter bufferedWrite = null; try { bufferedWrite = new BufferedWriter(new FileWriter("C:\Users\Administrator\Desktop\2.txt",true)); bufferedWrite.write("hello java file writer "); } catch(IOException e) { e.printStackTrace(); } finally { if ( bufferedWrite != null ) { bufferedWrite.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
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-mm-dd hh:mm:ss"); String d = "2008-07-10 20:23:30"; try { Date date = simpleDateFormat.parse(d); System.out.println(date.toString()); } catch (ParseException e) { // TODO Auto-generated catch block e.printStackTrace(); }
5.使用JDBC连接MySQL
package com.fpc.Test; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.util.Properties; public class MySqlJdbcTest { private String driverClass = "com.mysql.jdbc.Driver"; private Connection connection; //connection public void init(FileInputStream fs) throws IOException, ClassNotFoundException, SQLException { Properties properties = new Properties(); properties.load(fs); String url = properties.getProperty("url"); String username = properties.getProperty("name"); String password = properties.getProperty("password"); Class.forName(driverClass); connection = DriverManager.getConnection(url,username,password); } //fetch public void fetch () throws SQLException { String sql = "select * from student"; PreparedStatement ps = connection.prepareStatement(sql); ResultSet rs = ps.executeQuery(); while ( rs.next() ) { System.out.println(rs.getString("s_name")); } rs.close(); ps.close(); } public static void main(String[] args) throws ClassNotFoundException, IOException, SQLException { MySqlJdbcTest test = new MySqlJdbcTest(); File file = new File("C:\Users\Administrator\Desktop\db.properties"); FileInputStream fs = new FileInputStream(file); test.init(fs); test.fetch(); } }
6.把Java.util.Date转成Java.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(); //magic number for windows,64MB -32Kb int maxCount = (64*1024*1024) - (32*1024); long size = inChannel.size(); int position = 0; while ( position < size ) { position += inChannel.transferTo(position, maxCount, outChannel); } if ( inChannel != null ) { inChannel.close(); } if ( outChannel != null ) { outChannel.close(); } }
8.创建JSON格式的数据
下载jar文件 json-rpc-1.0.jar
JSONObject json = new JSONObject(); json.put("name","fpc"); json.put("age", 22); String str = json.toString();
9.使用iText JAR生成PDF
public static void main(String[] args) throws IOException, DocumentException{ OutputStream file = new FileOutputStream(new File("C:\Users\Administrator\Desktop\test.pdf")); Document document = new Document(); PdfWriter.getInstance(document, file); document.open(); document.add(new Paragraph("Hello Fpc")); document.add(new Paragraph(new Date().toString())); document.close(); file.close(); }
10.抓屏程序
public void captureScreen(String fileName) throws IOException, AWTException { 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)); }
11.解析/读取XML文件
package com.fpc.Test; import java.io.File; import java.io.IOException; import javax.xml.parsers.DocumentBuilder; import javax.xml.parsers.DocumentBuilderFactory; import javax.xml.parsers.ParserConfigurationException; import org.w3c.dom.Document; import org.w3c.dom.Element; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.xml.sax.SAXException; public class XMLParser { public void getAllUserNames(String fileName) throws ParserConfigurationException, SAXException, IOException { DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db = dbf.newDocumentBuilder(); File file = new File(fileName); if ( file.exists() ) { Document doc = db.parse(file); Element docElement = doc.getDocumentElement(); //Print root element of the document System.out.println("Root element of the document: " + docElement.getNodeName()); NodeList studentList = docElement.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 element = (Element) node; NodeList nodeList = element.getElementsByTagName("name"); System.out.println("Name : " + nodeList.item(0).getChildNodes().item(0).getNodeValue()); nodeList = element.getElementsByTagName("grade"); System.out.println("Grade : " + nodeList.item(0).getChildNodes().item(0).getNodeValue()); nodeList = element.getElementsByTagName("age"); System.out.println("Age : " + nodeList.item(0).getChildNodes().item(0).getNodeValue()); } else { System.exit(1); } } } } } public static void main( String[] args ) throws ParserConfigurationException, SAXException, IOException { XMLParser xmlparser = new XMLParser(); xmlparser.getAllUserNames("C:\Users\Administrator\Desktop\test.xml"); } }
12.把Array转成Map
public static void main( String[] args ) { String[][] countries = { { "United States", "New York" }, { "United Kingdom", "London" }, { "Netherland", "Amsterdam" }, { "Japan", "Tokyo" }, { "France", "Paris" } }; Map<Object, Object> countriesCapitical = ArrayUtils.toMap(countries); //traverse for ( Map.Entry<Object, Object> entry : countriesCapitical.entrySet()) { System.out.println(entry.getKey() + " " + entry.getValue()); } }