...
| Code Block | ||
|---|---|---|
| ||
public final class WebRequestAnalyzer {
private final Vector<WebRequest> requests = new Vector<WebRequest>();
public boolean addWebRequest(WebRequest request) {
return requests.add(new WebRequest(request.getBandwidth(),
request.getResponseTime()));
}
public double getAverageBandwidth() {
if (requests.size() == 0) {
throw new IllegalStateException("The vector is empty!");
}
return calculateAverageBandwidth(0, 0);
}
public double getAverageResponseTime() {
if (requests.size() == 0) {
throw new IllegalStateException("The vector is empty!");
}
return calculateAverageResponseTime(requests.size() - 1, 0);
}
private double calculateAverageBandwidth(int i, long bandwidth) {
if (i == requests.size()) {
return bandwidth / requests.size();
}
synchronized (requests.elementAt(i)) {
bandwidth += requests.get(i).getBandwidth();
// Acquires locks in increasing order
return calculateAverageBandwidth(++i, bandwidth);
}
}
private double calculateAverageResponseTime(int i, long responseTime) {
if (i <= -1) {
return responseTime / requests.size();
}
synchronized (requests.elementAt(i)) {
responseTime += requests.get(i).getResponseTime();
// Acquires locks in decreasing order
return calculateAverageResponseTime(--i, responseTime);
}
}
}
|
The monitoring application is built around the WebRequestAnalyzer class, which maintains a list of web requests using the requests vector and includes the addWebRequest() setter method. Any thread can request the average bandwidth or average response time of all web requests by invoking the getAverageBandwidth() and getAverageResponseTime() methods.
...
| Code Block | ||
|---|---|---|
| ||
public final class WebRequestAnalyzer {
private final Vector<WebRequest> requests = new Vector<WebRequest>();
public boolean addWebRequest(WebRequest request) {
return requests.add(new WebRequest(request.getBandwidth(),
request.getResponseTime()));
}
public double getAverageBandwidth() {
if (requests.size() == 0) {
throw new IllegalStateException("The vector is empty!");
}
return calculateAverageBandwidth(0, 0);
}
public double getAverageResponseTime() {
if (requests.size() == 0) {
throw new IllegalStateException("The vector is empty!");
}
return calculateAverageResponseTime(0, 0);
}
private double calculateAverageBandwidth(int i, long bandwidth) {
if (i == requests.size()) {
return bandwidth / requests.size();
}
synchronized (requests.elementAt(i)) { // Acquires locks in increasing order
bandwidth += requests.get(i).getBandwidth();
return calculateAverageBandwidth(++i, bandwidth);
}
}
private double calculateAverageResponseTime(int i, long responseTime) {
if (i == requests.size()) {
return responseTime / requests.size();
}
synchronized (requests.elementAt(i)) {
responseTime += requests.get(i).getResponseTime();
// Acquires locks in increasing order
return calculateAverageResponseTime(++i, responseTime);
}
}
}
|
...
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
LCK07-J | low | likely | high | P3 | L3 |
Automated Detection
SureLogic Flashlight can detect violations of this rule. It flags both the noncompliant code examples by specifying: "potential for deadlock."
...
Related Guidelines
Bibliography
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="f9a332c335259bbf-cb542644-486548c2-9670b787-9e77dd7da56e78597524cbd9"><ac:plain-text-body><![CDATA[ | [[JLS 2005 | AA. Bibliography#JLS 05]] | [Chapter 17, Threads and Locks | http://java.sun.com/docs/books/jls/third_edition/html/memory.html] | ]]></ac:plain-text-body></ac:structured-macro> |
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="e62f76c7fb4c6979-8c4c6483-46aa45ca-b8f28ff1-9b67d5fb52d6a538f2995116"><ac:plain-text-body><![CDATA[ | [[Halloway 2000 | AA. Bibliography#Halloway 00]] |
| ]]></ac:plain-text-body></ac:structured-macro> |
...