カウント
サーブレットでのカウント 書籍より引用
@ThreadSafe
public class CountingFactorizer extends GenericServlet implements Servlet {
private final AtomicLong count = new AtomicLong(0);
public long getCount() { return count.get(); }
public void service(ServletRequest req, ServletResponse resp) {
BigInteger i = extractFromRequest(req);
BigInteger[] factors = factor(i);
count.incrementAndGet();
encodeIntoResponse(resp, factors);
}
}
以下は、count変数の値を増やす部分が、安全ではない
@NotThreadSafe
public class UnsafeCountingFactorizer extends GenericServlet implements Servlet {
private long count = 0;
public long getCount() {
return count;
}
public void service(ServletRequest req, ServletResponse resp) {
BigInteger i = extractFromRequest(req);
BigInteger[] factors = factor(i);
++count;
encodeIntoResponse(resp, factors);
}
}