PrimeNumbers.java 注意,该Servlet要用到前面给出的ServletUtilities.java。另外还要用到:PrimeList.java,用于在后台线程中创建一个素数的Vector;Primes.java,用于随机生成BigInteger类型的大数字,检查它们是否是素数。(此处略去PrimeList.java和Primes.java的代码。) package hall; import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.util.*; public class PrimeNumbers extends HttpServlet { private static Vector primeListVector = new Vector(); private static int maxPrimeLists = 30; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { int numPrimes = ServletUtilities.getIntParameter(request, "numPrimes", 50); int numDigits = ServletUtilities.getIntParameter(request, "numDigits", 120); PrimeList primeList = findPrimeList(primeListVector, numPrimes, numDigits); if (primeList == null) { primeList = new PrimeList(numPrimes, numDigits, true); synchronized(primeListVector) { if (primeListVector.size() >= maxPrimeLists) primeListVector.removeElementAt(0); primeListVector.addElement(primeList); } } Vector currentPrimes = primeList.getPrimes(); int numCurrentPrimes = currentPrimes.size(); int numPrimesRemaining = (numPrimes - numCurrentPrimes); boolean isLastResult = (numPrimesRemaining == 0); if (!isLastResult) { response.setHeader("Refresh", "5"); } response.setContentType("text/html"); PrintWriter out = response.getWriter(); String title = "Some " + numDigits + "-Digit Prime Numbers"; out.println(ServletUtilities.headWithTitle(title) + "<BODY BGCOLOR=\"#FDF5E6\">\n" + "<H2 ALIGN=CENTER>" + title + "</H2>\n" + "<H3>Primes found with " + numDigits + " or more digits: " + numCurrentPrimes + ".</H3>"); if (isLastResult) out.println("<B>Done searching.</B>"); else out.println("<B>Still looking for " + numPrimesRemaining + " more<BLINK>...</BLINK></B>"); out.println("<OL>"); for(int i=0; i<numCurrentPrimes; i++) { out.println(" <LI>" + currentPrimes.elementAt(i)); } out.println("</OL>"); out.println("</BODY></HTML>"); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } // 检查是否存在同类型请求(已经完成,或者正在计算)。 // 如存在,则返回现有结果而不是启动新的后台线程。 private PrimeList findPrimeList(Vector primeListVector, int numPrimes, int numDigits) { synchronized(primeListVector) { for(int i=0; i<primeListVector.size(); i++) { PrimeList primes = (PrimeList)primeListVector.elementAt(i); if ((numPrimes == primes.numPrimes()) && (numDigits == primes.numDigits())) return(primes); } return(null); } } } PrimeNumbers.html <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML> <HEAD> <TITLE>大素数计算</TITLE> </HEAD> <CENTER> <BODY BGCOLOR="#FDF5E6"> <FORM ACTION="/servlet/hall.PrimeNumbers"> <B>要计算几个素数:</B> <INPUT TYPE="TEXT" NAME="numPrimes" VALUE=25 SIZE=4><BR> <B>每个素数的位数:</B> <INPUT TYPE="TEXT" NAME="numDigits" VALUE=150 SIZE=3><BR> <INPUT TYPE="SUBMIT" VALUE="开始计算"> </FORM> </CENTER> </BODY> </HTML> |
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