20非常有用的Java程序片段(3)

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 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();
    }
}

16. 解析/读取XML 文件

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：

ackage 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");
    }
}