##### Overview

- Download PMD 5.0.4
- What's new in PMD 5.0.4
- PMD in the news
- PMD-related products and books
- Best practices
- Future directions
- Similar projects
- Credits
- License
- What does 'PMD' mean?

##### Usage

- Installation
- Command line usage
- Ant task usage
- Maven plugin usage
- Mvn plugin usage
- IDE plugin usage
- Suppressing warnings
- Finding duplicated code
- JSP support

##### Customizing PMD

- Compiling PMD
- How to write a rule
- Writing XPath rules
- How to make a rule set
- How it works
- Rule guidelines
- PMD developers information
- PMD Release Process

##### For example

- Run PMD on a Sourceforge project

##### Misc.

- XPath tutorial (Gregorian)

##### Rule Sets

- ecmascript
  - Basic Ecmascript
  - Braces
  - Unnecessary
- java
  - Android
  - Basic
  - Braces
  - Clone Implementation
  - Code Size
  - Comments
  - Controversial
  - Coupling
  - Design
  - Empty Code
  - Finalizer
  - Import Statements
  - J2EE
  - JavaBeans
  - JUnit
  - Jakarta Commons Logging
  - Java Logging
  - Migration
  - Naming
  - Optimization
  - Strict Exceptions
  - String and StringBuffer
  - Security Code Guidelines
  - Type Resolution
  - Unnecessary
  - Unused Code
- jsp
  - Basic JSF
  - Basic JSP
- xml
  - Basic XML
- xsl
  - XPath in XSL

##### Project Documentation

- Project Information
- Project Reports

## Code Size

The Code Size ruleset contains rules that find problems related to code size or complexity.

### NPathComplexity

Since: PMD 3.9

The NPath complexity of a method is the number of acyclic execution paths through that method. A threshold of 200 is generally considered the point where measures should be taken to reduce complexity and increase readability.

This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.codesize.NPathComplexityRule

Example(s):

    void bar() {	// this is something more complex than it needs to be,
    	if (y) {	// it should be broken down into smaller methods or functions
    		for (j = 0; j < m; j++) {
    			if (j > r) {
    				doSomething();
    				while (f < 5 ) {
    					anotherThing();
    					f -= 27;
    					}
    				} else {
    					tryThis();
    				}
    			}
    		}
    		if ( r - n > 45) {
    		   while (doMagic()) {
    		      findRabbits();
    		   }
    		}
    		try {
    			doSomethingDangerous();
    		} catch (Exception ex) {
    			makeAmends();
    			} finally {
    				dontDoItAgain();
    				}
    	}
    }

This rule has the following properties:

Name | Default Value | Description
--- | --- | ---
violationSuppressRegex |  | Suppress violations with messages matching a regular expression
violationSuppressXPath |  | Suppress violations on nodes which match a given relative XPath expression.
topscore |  | Top score value
minimum | 200.0 | Minimum reporting threshold
sigma |  | Sigma value

### ExcessiveMethodLength

Since: PMD 0.6

When methods are excessively long this usually indicates that the method is doing more than its name/signature might suggest. They also become challenging for others to digest since excessive scrolling causes readers to lose focus. Try to reduce the method length by creating helper methods and removing any copy/pasted code.

This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.codesize.ExcessiveMethodLengthRule

Example(s):

    public void doSomething() {
    	System.out.println("Hello world!");
    	System.out.println("Hello world!");
    		// 98 copies omitted for brevity.
    }

This rule has the following properties:

Name | Default Value | Description
--- | --- | ---
violationSuppressRegex |  | Suppress violations with messages matching a regular expression
violationSuppressXPath |  | Suppress violations on nodes which match a given relative XPath expression.
topscore |  | Top score value
minimum | 100.0 | Minimum reporting threshold
sigma |  | Sigma value

### ExcessiveParameterList

Since: PMD 0.9

Methods with numerous parameters are a challenge to maintain, especially if most of them share the same datatype. These situations usually denote the need for new objects to wrap the numerous parameters.

This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.codesize.ExcessiveParameterListRule

Example(s):

    public void addPerson(		// too many arguments liable to be mixed up
    	int birthYear, int birthMonth, int birthDate, int height, int weight, int ssn) {

    	. . . .
    }

    public void addPerson(		// preferred approach
    	Date birthdate, BodyMeasurements measurements, int ssn) {

    	. . . .
    }

This rule has the following properties:

Name | Default Value | Description
--- | --- | ---
violationSuppressRegex |  | Suppress violations with messages matching a regular expression
violationSuppressXPath |  | Suppress violations on nodes which match a given relative XPath expression.
topscore |  | Top score value
minimum | 10.0 | Minimum reporting threshold
sigma |  | Sigma value

### ExcessiveClassLength

Since: PMD 0.6

Excessive class file lengths are usually indications that the class may be burdened with excessive responsibilities that could be provided by external classes or functions. In breaking these methods apart the code becomes more managable and ripe for reuse.

This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.codesize.ExcessiveClassLengthRule

Example(s):

    public class Foo {
    	public void bar1() {
        // 1000 lines of code
    	}
    	public void bar2() {
        // 1000 lines of code
    	}
        public void bar3() {
        // 1000 lines of code
    	}

        public void barN() {
        // 1000 lines of code
    	}
    }

This rule has the following properties:

Name | Default Value | Description
--- | --- | ---
violationSuppressRegex |  | Suppress violations with messages matching a regular expression
violationSuppressXPath |  | Suppress violations on nodes which match a given relative XPath expression.
topscore |  | Top score value
minimum | 1000.0 | Minimum reporting threshold
sigma |  | Sigma value

### CyclomaticComplexity

Since: PMD 1.03

Complexity directly affects maintenance costs is determined by the number of decision points in a method plus one for the method entry. The decision points include 'if', 'while', 'for', and 'case labels' calls. Generally, numbers ranging from 1-4 denote low complexity, 5-7 denote moderate complexity, 8-10 denote high complexity, and 11+ is very high complexity.

This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.codesize.CyclomaticComplexityRule

Example(s):

    public class Foo {		// This has a Cyclomatic Complexity = 12
    1   public void example()  {
    2       if (a == b)  {
    3           if (a1 == b1) {
                    fiddle();
    4           } else if a2 == b2) {
                    fiddle();
                }  else {
                    fiddle();
                }
    5       } else if (c == d) {
    6           while (c == d) {
                    fiddle();
                }
    7        } else if (e == f) {
    8           for (int n = 0; n < h; n++) {
                    fiddle();
                }
            } else{
                switch (z) {
    9               case 1:
                        fiddle();
                        break;
    10              case 2:
                        fiddle();
                        break;
    11              case 3:
                        fiddle();
                        break;
    12              default:
                        fiddle();
                        break;
                }
            }
        }
    }

This rule has the following properties:

Name | Default Value | Description
--- | --- | ---
violationSuppressRegex |  | Suppress violations with messages matching a regular expression
violationSuppressXPath |  | Suppress violations on nodes which match a given relative XPath expression.
showMethodsComplexity | true | Add method average violations to the report
showClassesComplexity | true | Add class average violations to the report
reportLevel | 10 | Cyclomatic Complexity reporting threshold

### ExcessivePublicCount

Since: PMD 1.04

Classes with large numbers of public methods and attributes require disproportionate testing efforts since combinational side effects grow rapidly and increase risk. Refactoring these classes into smaller ones not only increases testability and reliability but also allows new variations to be developed easily.

This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.codesize.ExcessivePublicCountRule

Example(s):

    public class Foo {
    	public String value;
    	public Bar something;
    	public Variable var;
     // [... more more public attributes ...]

    	public void doWork() {}
    	public void doMoreWork() {}
    	public void doWorkAgain() {}
     // [... more more public methods ...]
    }

This rule has the following properties:

Name | Default Value | Description
--- | --- | ---
violationSuppressRegex |  | Suppress violations with messages matching a regular expression
violationSuppressXPath |  | Suppress violations on nodes which match a given relative XPath expression.
topscore |  | Top score value
minimum | 45.0 | Minimum reporting threshold
sigma |  | Sigma value

### TooManyFields

Since: PMD 3.0

Classes that have too many fields can become unwieldy and could be redesigned to have fewer fields, possibly through grouping related fields in new objects. For example, a class with individual city/state/zip fields could park them within a single Address field.

This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.codesize.TooManyFieldsRule

Example(s):

    public class Person {	// too many separate fields
       int birthYear;
       int birthMonth;
       int birthDate;
       float height;
       float weight;
    }

    public class Person {	// this is more manageable
       Date birthDate;
       BodyMeasurements measurements;
    }

This rule has the following properties:

Name | Default Value | Description
--- | --- | ---
violationSuppressRegex |  | Suppress violations with messages matching a regular expression
violationSuppressXPath |  | Suppress violations on nodes which match a given relative XPath expression.
maxfields | 15 | Max allowable fields

### NcssMethodCount

Since: PMD 3.9

This rule uses the NCSS (Non-Commenting Source Statements) algorithm to determine the number of lines of code for a given method. NCSS ignores comments, and counts actual statements. Using this algorithm, lines of code that are split are counted as one.

This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.codesize.NcssMethodCountRule

Example(s):

    public class Foo extends Bar {
     public int methd() {
         super.methd();

     //this method only has 1 NCSS lines
          return 1;
     }
    }

This rule has the following properties:

Name | Default Value | Description
--- | --- | ---
violationSuppressRegex |  | Suppress violations with messages matching a regular expression
violationSuppressXPath |  | Suppress violations on nodes which match a given relative XPath expression.
topscore |  | Top score value
minimum | 100.0 | Minimum reporting threshold
sigma |  | Sigma value

### NcssTypeCount

Since: PMD 3.9

This rule uses the NCSS (Non-Commenting Source Statements) algorithm to determine the number of lines of code for a given type. NCSS ignores comments, and counts actual statements. Using this algorithm, lines of code that are split are counted as one.

This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.codesize.NcssTypeCountRule

Example(s):

    public class Foo extends Bar {
     public Foo() {
     //this class only has 6 NCSS lines
         super();

          super.foo();
     }
    }

This rule has the following properties:

Name | Default Value | Description
--- | --- | ---
violationSuppressRegex |  | Suppress violations with messages matching a regular expression
violationSuppressXPath |  | Suppress violations on nodes which match a given relative XPath expression.
topscore |  | Top score value
minimum | 1500.0 | Minimum reporting threshold
sigma |  | Sigma value

### NcssConstructorCount

Since: PMD 3.9

This rule uses the NCSS (Non-Commenting Source Statements) algorithm to determine the number of lines of code for a given constructor. NCSS ignores comments, and counts actual statements. Using this algorithm, lines of code that are split are counted as one.

This rule is defined by the following Java class: net.sourceforge.pmd.lang.java.rule.codesize.NcssConstructorCountRule

Example(s):

    public class Foo extends Bar {
     public Foo() {
         super();

     //this constructor only has 1 NCSS lines
          super.foo();
     }
    }

This rule has the following properties:

Name | Default Value | Description
--- | --- | ---
violationSuppressRegex |  | Suppress violations with messages matching a regular expression
violationSuppressXPath |  | Suppress violations on nodes which match a given relative XPath expression.
topscore |  | Top score value
minimum | 100.0 | Minimum reporting threshold
sigma |  | Sigma value

### TooManyMethods

Since: PMD 4.2

A class with too many methods is probably a good suspect for refactoring, in order to reduce its complexity and find a way to have more fine grained objects.

     //ClassOrInterfaceDeclaration/ClassOrInterfaceBody
         [
          count(descendant::MethodDeclarator[
             not (
                    starts-with(@Image,'get')
                    or
                    starts-with(@Image,'set')
                    or
                    starts-with(@Image,'is')
                )
          ]) > $maxmethods
       ]

This rule has the following properties:

Name | Default Value | Description
--- | --- | ---
maxmethods | 10 | The method count reporting threshold