2-《Java并发编程实战》(Java Concurrency in Practice) 代码示例

说明

这是针对《Java并发编程实战》(Java Concurrency in Practice)一书中的示例代码进行扩展，并且进行验证的完整代码，具体背景可看这篇文章：1-《Java并发编程实战》(Java Concurrency in Practice) 代码示例

下面的示例代码都是针对书中的（不完整的）代码扩展，不再介绍具体上下文背景（如果你也在看这本书，可以拿我这里的示例代码做个参考，并欢迎提出意见和建议）

程序清单2-5

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.concurrent.atomic.AtomicReference;/*** @DESCRIPTION:* @USER: shg* @DATE: 2024/1/13 11:15*/
public class UnsafeCachingFactorizer extends HttpServlet {private final AtomicReference<BigInteger> lastNumber = new AtomicReference<>();private final AtomicReference<BigInteger[]> lastFactors = new AtomicReference<>();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {BigInteger i = extractFromRequest(req);if (i.equals(lastNumber.get())) {encodeIntoResponse(resp, i, lastFactors.get());} else {BigInteger[] factors = factor(i);lastNumber.set(i);lastFactors.set(factors);encodeIntoResponse(resp, i, lastFactors.get());}}private BigInteger extractFromRequest(HttpServletRequest req) {return new BigInteger(req.getParameter("key"));}private void encodeIntoResponse(HttpServletResponse resp, BigInteger i, BigInteger[] factors) throws IOException {System.out.println(i + "--->" + Arrays.asList(factors));resp.setContentType("text/html;charset=utf-8");PrintWriter writer = resp.getWriter();writer.println("<html><body>");writer.println("<h1>" + i + "因数分解结果为：" + Arrays.asList(factors));writer.println("</body></html>");}private BigInteger[] factor(BigInteger number) {List<BigInteger> factors = new ArrayList<>();BigInteger divisor = BigInteger.valueOf(2);while (number.compareTo(BigInteger.ONE) > 0) {if (number.mod(divisor).equals(BigInteger.ZERO)) {number = number.divide(divisor);factors.add(divisor);} else {divisor = divisor.add(BigInteger.ONE);}}return factors.toArray(new BigInteger[0]);}
}