生成100000以内的素数XML文件的Demo(Jdom写成)

</pre><pre name="code" class="java">

<pre name="code" class="java">public class TestPrimeXml {
	private static String fileName = "Primes.xml";
	//获取源文件路径
	private static String path = System.getProperty("user.dir") + File.separator + "src" + File.separator + fileName;

	public static void main(String[] args) {
		//创建PrimeXML文档
		creatPrimeXML(100000);
		//输入一个数字,检验是否为质数,如果是则返回相应的下标位置,如果不是则打印其为合数
		checkNum(73897);
		Add();
	}
	
	//添加一些片段
	private static void Add() {
		try {
			//创建解析器
			SAXBuilder sb = new SAXBuilder();
			//获取要解析的目标文件
			File file = new File(path);
			//解析文件获取document
			Document document = sb.build(file);
			Element rooteElement = document.getRootElement();
			//获取子节点集合
			List<Element> eList = rooteElement.getChildren();
			for (Element element : eList) {
				element.setAttribute("name","wanglf");
			}
			rooteElement.setAttribute("name","wanglf");
			saveDocument(document);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	@SuppressWarnings("unchecked")
	private static void checkNum(int i) {
		if (!isPrimeBaidu(i)) {
			System.out.println(i + "是合数");
		} else {
			try {
				//创建解析器
				SAXBuilder sb = new SAXBuilder();
				//获取要解析的目标文件
				File file = new File(path);
				//解析文件获取document
				Document document = sb.build(file);
				//获取文档根节点
				Element rootElement = document.getRootElement();
				//获取指定节点的所有子节点
				List<Element> eList = rootElement.getChildren();
				for (Element element : eList) {
					if (element.getText().equals(i + "")) {
						System.out.println(i + "所在的id为:" + element.getAttributeValue("id"));
						System.exit(0);
					}
				}
			} catch (Exception e) {
				e.printStackTrace();
			}
		}

	}

	public static void creatPrimeXML(Integer s) {
		try {
			long f1 = System.nanoTime();
			Document document = getDocument(s);
			saveDocument(document);
			long f2 = System.nanoTime();
			//计算运行时间
			System.out.println("总共用时" + (f2 - f1) / 10e8 + "秒");
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	private static void saveDocument(Document document) throws Exception{
		//格式化
		Format format = Format.getPrettyFormat();
		//输出文本
		XMLOutputter out = new XMLOutputter(format);
		out.output(document,new FileOutputStream(path));
	}

	/**
	 * 
	 * @param n
	 * @return Document
	 */
	private static Document getDocument(Integer n) {
		Element rootElement = new Element("primes");
		int s = 1;
		for (int i = 2; i <= n; i++) {
			if (isPrimeBaidu(i)) {
				Element element = new Element("prime");
				element.setAttribute("id",s + "");
				element.setText(i + "");
				rootElement.addContent(element);
				s++;
			}
		}
		Document document = new Document(rootElement);
		return document;

	}

	/**
	 * 一个很优秀的素数计算方法
	 * @param n
	 * @return boolean
	 */
	public static boolean isPrimeBaidu(long n) {

		if (n <= 3) {
			return n > 1;
		} else if (n % 2 == 0 || n % 3 == 0) {
			return false;
		} else {
			for (int i = 5; i * i <= n; i += 6) {
				if (n % i == 0 || n % (i + 2) == 0) {
					return false;
				}
			}
			return true;
		}
	}
}

（编辑：李大同）

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