This rule is defined by the following Java class: net.sourceforge.pmd.rules.strings.InsufficientStringBufferDeclaration
Example:
public class Foo { void bar() { StringBuffer bad = new StringBuffer(); bad.append("This is a long string, will exceed the default 16 characters");//bad StringBuffer good = new StringBuffer(41); good.append("This is a long string, which is pre-sized");//good } }