Not all classes in the standard Java library were written to be thread-safe. Using them in a multi-threaded manner is highly likely to cause data
problems or exceptions at runtime.
This rule raises an issue when an instance of Calendar
, DateFormat
, javax.xml.xpath.XPath
, or
javax.xml.validation.SchemaFactory
is marked static
.
Noncompliant Code Example
public class MyClass {
private static SimpleDateFormat format = new SimpleDateFormat("HH-mm-ss"); // Noncompliant
private static Calendar calendar = Calendar.getInstance(); // Noncompliant
Compliant Solution
public class MyClass {
private SimpleDateFormat format = new SimpleDateFormat("HH-mm-ss");
private Calendar calendar = Calendar.getInstance();