Adobe-Consulting-Services/acs-aem-commons

        final Dictionary<String, Object> properties = new Hashtable<>();

Close

Early classes of the Java API, such as Vector, Hashtable and StringBuffer, were synchronized to make them thread-safe. Unfortunately, synchronization has a big negative impact on performance, even when using these collections from a single thread.

It is better to use their new unsynchronized replacements:

• ArrayList or LinkedList instead of Vector
• Deque instead of Stack
• HashMap instead of Hashtable
• StringBuilder instead of StringBuffer

Even when used in synchronized context, you should think twice before using it, since it's usage can be tricky. If you are confident the usage is legitimate, you can safely ignore this warning.

Noncompliant Code Example

Vector cats = new Vector();

Compliant Solution

ArrayList cats = new ArrayList();

Exceptions

Use of those synchronized classes is ignored in the signatures of overriding methods.

@Override
public Vector getCats() {...}

 * ACS AEM Commons

Close

Checks the header of a source file against a header that contains aregular expression for each line of the source header.

Rationale: In some projects checking against afixed header is not sufficient, e.g. the header might require acopyright line where the year information is not static.

For example, consider the following header:

<source><br>line 1: ^/{71}$<br>line 2: ^// checkstyle:$<br>line 3: ^// Checks Java source code for adherence to a set of rules\.$<br>line 4: ^// Copyright \(C\) \d\d\d\d Oliver Burn$<br>line 5: ^// Last modification by \$Author.*\$$<br>line 6: ^/{71}$<br>line 7:<br>line 8: ^package<br>line 9:<br>line 10: ^import<br>line 11:<br>line 12: ^/\*\*<br>line 13: ^ \*([^/]|$)<br>line 14: ^ \*/<br> </source>

Lines 1 and 6 demonstrate a more compact notation for 71 '/'characters. Line 4 enforces that the copyright notice includes afour digit year. Line 5 is an example how to enforce revisioncontrol keywords in a file header. Lines 12-14 is a template forjavadoc (line 13 is so complicated to remove conflict with and ofjavadoc comment). Lines 7, 9 and 11 will be treated as '^$' andwill forcefully expect the line to be empty.

Different programming languages have different comment syntaxrules, but all of them start a comment with a non-wordcharacter. Hence you can often use the non-word characterclass to abstract away the concrete comment syntax and allowchecking the header for different languages with a singleheader definition. For example, consider the following headerspecification (note that this is not the full Apache licenseheader):

<source><br>line 1: ^#!<br>line 2: ^&lt;\?xml.*&gt;$<br>line 3: ^\W*$<br>line 4: ^\W*Copyright 2006 The Apache Software Foundation or its licensors, as applicable\.$<br>line 5: ^\W*Licensed under the Apache License, Version 2\.0 \(the "License"\);$<br>line 6: ^\W*$<br> </source>

Lines 1 and 2 leave room for technical header lines, e.g. the"#!/bin/sh" line in Unix shell scripts, or the XML file headerof XML files. Set the multiline property to "1, 2" so theselines can be ignored for file types where they do no apply.Lines 3 through 6 define the actual header content. Note howlines 2, 4 and 5 use escapes for characters that have specialregexp semantics.

In default configuration, if header is not specified, the default valueof header is set to null and the check does not rise any violations.

This documentation is written and maintained by the Checkstyle community and is covered under the same license as the Checkstyle project.