Since: PMD 0.1
Empty Catch Block finds instances where an exception is caught, but nothing is done. In most circumstances, this swallows an exception which should either be acted on or reported.
This rule is defined by the following XPath expression:
//CatchStatement [count(Block/BlockStatement) = 0 and ($allowCommentedBlocks != 'true' or Block/@containsComment = 'false')] [FormalParameter/Type/ReferenceType /ClassOrInterfaceType[@Image != 'InterruptedException' and @Image != 'CloneNotSupportedException'] ]
Example:
public void doSomething() {
try {
FileInputStream fis = new FileInputStream("/tmp/bugger");
} catch (IOException ioe) {
// not good
}
}
This rule has the following properties:
| Name | Default value | Description |
|---|---|
| allowCommentedBlocks | Empty blocks containing comments will be skipped |
Since: PMD 0.1
Empty If Statement finds instances where a condition is checked but nothing is done about it.
This rule is defined by the following XPath expression:
//IfStatement/Statement [EmptyStatement or Block[count(*) = 0]]
Example:
public class Foo {
void bar(int x) {
if (x == 0) {
// empty!
}
}
}
Since: PMD 0.2
Empty While Statement finds all instances where a while statement does nothing. If it is a timing loop, then you should use Thread.sleep() for it; if it's a while loop that does a lot in the exit expression, rewrite it to make it clearer.
This rule is defined by the following XPath expression:
//WhileStatement/Statement[./Block[count(*) = 0] or ./EmptyStatement]
Example:
public class Foo {
void bar(int a, int b) {
while (a == b) {
// empty!
}
}
}
Since: PMD 0.4
Avoid empty try blocks - what's the point?
This rule is defined by the following XPath expression:
//TryStatement/Block[1][count(*) = 0]
Example:
public class Foo {
public void bar() {
try {
} catch (Exception e) {
e.printStackTrace();
}
}
}
Since: PMD 0.4
Avoid empty finally blocks - these can be deleted.
This rule is defined by the following XPath expression:
//FinallyStatement[count(Block/BlockStatement) = 0]
Example:
public class Foo {
public void bar() {
try {
int x=2;
} finally {
// empty!
}
}
}
Since: PMD 1.0
Avoid empty switch statements.
This rule is defined by the following XPath expression:
//SwitchStatement[count(*) = 1]
Example:
public class Foo {
public void bar() {
int x = 2;
switch (x) {
// once there was code here
// but it's been commented out or something
}
}
}
Since: PMD 1.0
Avoid jumbled loop incrementers - it's usually a mistake, and it's confusing even if it's what's intended.
This rule is defined by the following XPath expression:
//ForStatement [ ForUpdate/StatementExpressionList/StatementExpression/PostfixExpression/PrimaryExpression/PrimaryPrefix/Name/@Image = ancestor::ForStatement/ForInit//VariableDeclaratorId/@Image ]
Example:
public class JumbledIncrementerRule1 {
public void foo() {
for (int i = 0; i < 10; i++) {
for (int k = 0; k < 20; i++) {
System.out.println("Hello");
}
}
}
}
Since: PMD 1.02
Some for loops can be simplified to while loops - this makes them more concise.
This rule is defined by the following XPath expression:
//ForStatement [count(*) > 1] [not(ForInit)] [not(ForUpdate)] [not(Type and Expression and Statement)]
Example:
public class Foo {
void bar() {
for (;true;) true; // No Init or Update part, may as well be: while (true)
}
}
Since: PMD 0.1
Avoid unnecessary temporaries when converting primitives to Strings
This rule is defined by the following Java class: net.sourceforge.pmd.rules.UnnecessaryConversionTemporary
Example:
public String convert(int x) {
// this wastes an object
String foo = new Integer(x).toString();
// this is better
return Integer.toString(x);
}
Since: PMD 0.4
Override both public boolean Object.equals(Object other), and public int Object.hashCode(), or override neither. Even if you are inheriting a hashCode() from a parent class, consider implementing hashCode and explicitly delegating to your superclass.
This rule is defined by the following Java class: net.sourceforge.pmd.rules.OverrideBothEqualsAndHashcode
Example:
// this is bad
public class Bar {
public boolean equals(Object o) {
// do some comparison
}
}
// and so is this
public class Baz {
public int hashCode() {
// return some hash value
}
}
// this is OK
public class Foo {
public boolean equals(Object other) {
// do some comparison
}
public int hashCode() {
// return some hash value
}
}
Since: PMD 1.04
Partially created objects can be returned by the Double Checked Locking pattern when used in Java. An optimizing JRE may assign a reference to the baz variable before it creates the object the reference is intended to point to. For more details see http://www.javaworld.com/javaworld/jw-02-2001/jw-0209-double.html.
This rule is defined by the following Java class: net.sourceforge.pmd.rules.DoubleCheckedLocking
Example:
public class Foo {
Object baz;
Object bar() {
if(baz == null) { //baz may be non-null yet not fully created
synchronized(this){
if(baz == null){
baz = new Object();
}
}
}
return baz;
}
}
Since: PMD 1.05
Avoid returning from a finally block - this can discard exceptions.
This rule is defined by the following XPath expression:
//FinallyStatement//ReturnStatement
Example:
public class Bar {
public String foo() {
try {
throw new Exception( "My Exception" );
} catch (Exception e) {
throw e;
} finally {
return "A. O. K."; // Very bad.
}
}
}
Since: PMD 1.3
Avoid empty synchronized blocks - they're useless.
This rule is defined by the following XPath expression:
//SynchronizedStatement/Block[1][count(*) = 0]
Example:
public class Foo {
public void bar() {
synchronized (this) {
// empty!
}
}
}
Since: PMD 1.3
Avoid unnecessary return statements
This rule is defined by the following Java class: net.sourceforge.pmd.rules.basic.UnnecessaryReturn
Example:
public class Foo {
public void bar() {
int x = 42;
return;
}
}
Since: PMD 1.5
An empty static initializer was found.
This rule is defined by the following XPath expression:
//Initializer[@Static='true']/Block[count(*)=0]
Example:
public class Foo {
static {
// empty
}
}
Since: PMD 1.5
Do not use "if" statements that are always true or always false.
This rule is defined by the following XPath expression:
//IfStatement/Expression [count(PrimaryExpression)=1] /PrimaryExpression/PrimaryPrefix/Literal/BooleanLiteral
Example:
public class Foo {
public void close() {
if (true) {
// ...
}
}
}
Since: PMD 1.5
An empty statement (aka a semicolon by itself) that is not used as the sole body of a for loop or while loop is probably a bug. It could also be a double semicolon, which is useless and should be removed.
This rule is defined by the following XPath expression:
//EmptyStatement [not( ../../../ForStatement or ../../../WhileStatement or ../../../BlockStatement/ClassOrInterfaceDeclaration or ../../../../../../ForStatement/Statement[1] /Block[1]/BlockStatement[1]/Statement/EmptyStatement or ../../../../../../WhileStatement/Statement[1] /Block[1]/BlockStatement[1]/Statement/EmptyStatement) ]
Example:
public class MyClass {
public void doit() {
// this is probably not what you meant to do
;
// the extra semicolon here this is not necessary
System.out.println("look at the extra semicolon");;
}
}
Since: PMD 1.2
Avoid instantiating Boolean objects; you can reference Boolean.TRUE, Boolean.FALSE, or call Boolean.valueOf() instead.
This rule is defined by the following Java class: net.sourceforge.pmd.rules.basic.BooleanInstantiation
Example:
public class Foo {
Boolean bar = new Boolean("true"); // just do a Boolean bar = Boolean.TRUE;
Boolean buz = Boolean.valueOf(false); // just do a Boolean buz = Boolean.FALSE;
}
Since: PMD 3.0
When a class has the final modifier, all the methods are automatically final.
This rule is defined by the following XPath expression:
//ClassOrInterfaceDeclaration[@Final='true' and @Interface='false'] /ClassOrInterfaceBody/ClassOrInterfaceBodyDeclaration/MethodDeclaration[@Final='true']
Example:
public final class Foo {
// This final modifier is not necessary, since the class is final
// and thus, all methods are final
private final void foo() {
}
}
Since: PMD 3.1
Sometimes two 'if' statements can be consolidated by separating their conditions with a boolean short-circuit operator.
This rule is defined by the following XPath expression:
//IfStatement[@Else='false']/Statement /IfStatement[@Else='false'] | //IfStatement[@Else='false']/Statement /Block[count(BlockStatement)=1]/BlockStatement /Statement/IfStatement[@Else='false']
Example:
public class Foo {
void bar() {
if (x) {
if (y) {
// do stuff
}
}
}
}
Since: PMD 3.3
The overriding method merely calls the same method defined in a superclass
This rule is defined by the following Java class: net.sourceforge.pmd.rules.UselessOverridingMethod
Example:
public void foo(String bar) {
super.foo(bar); //Why bother overriding?
}
Example:
public String foo() {
return super.foo(); //Why bother overriding?
}
Example:
@Id
public Long getId() {
return super.getId(); //OK if 'ignoreAnnotations' is false, which is the default behavior
}
This rule has the following properties:
| Name | Default value | Description |
|---|---|---|
| ignoreAnnotations | false | Ignore annotations |
Since: PMD 3.4
if you need to get an array of a class from your Collection, you should pass an array of the desidered class as the parameter of the toArray method. Otherwise you will get a ClassCastException.
This rule is defined by the following XPath expression:
//CastExpression[Type/ReferenceType/ClassOrInterfaceType[@Image != "Object"]]//PrimaryExpression [ PrimaryPrefix/Name[ends-with(@Image, '.toArray')] and PrimarySuffix/Arguments[count(*) = 0] and count(PrimarySuffix) = 1 ]
Example:
import java.util.ArrayList;
import java.util.Collection;
public class Test {
public static void main(String[] args) {
Collection c=new ArrayList();
Integer obj=new Integer(1);
c.add(obj);
// this would trigger the rule (and throw a ClassCastException
if executed)
Integer[] a=(Integer [])c.toArray();
// this wouldn't trigger the rule
Integer[] b=(Integer [])c.toArray(new Integer[c.size()]);
}
}
Since: PMD 3.4
One might assume that "new BigDecimal(.1)" is exactly equal to .1, but it is actually equal to .1000000000000000055511151231257827021181583404541015625. This is so because .1 cannot be represented exactly as a double (or, for that matter, as a binary fraction of any finite length). Thus, the long value that is being passed in to the constructor is not exactly equal to .1, appearances notwithstanding. The (String) constructor, on the other hand, is perfectly predictable: 'new BigDecimal(".1")' is exactly equal to .1, as one would expect. Therefore, it is generally recommended that the (String) constructor be used in preference to this one.
This rule is defined by the following XPath expression:
//AllocationExpression[ClassOrInterfaceType[@Image="BigDecimal"] and ./Arguments/ArgumentList /Expression/PrimaryExpression/PrimaryPrefix/Literal[(not (ends-with (@Image,'"'))) and contains(@Image,".")]]
Example:
import java.math.BigDecimal;
public class Test {
public static void main(String[] args) {
// this would trigger the rule
BigDecimal bd=new BigDecimal(1.123);
// this wouldn't trigger the rule
BigDecimal bd=new BigDecimal("1.123");
// this wouldn't trigger the rule
BigDecimal bd=new BigDecimal(12);
}
}
Since: PMD 3.5
An operation on an Immutable object (String, BigDecimal or BigInteger) won't change the object itself. The result of the operation is a new object. Therefore, ignoring the operation result is an error.
This rule is defined by the following Java class: net.sourceforge.pmd.rules.UselessOperationOnImmutable
Example:
import java.math.*;
class Test {
void method1() {
BigDecimal bd=new BigDecimal(10);
bd.add(new BigDecimal(5)); // this will trigger the rule
}
void method2() {
BigDecimal bd=new BigDecimal(10);
bd = bd.add(new BigDecimal(5)); // this won't trigger the rule
}
}
Since: PMD 3.5
The null check here is misplaced. if the variable is null you'll get a NullPointerException. Either the check is useless (the variable will never be "null") or it's incorrect.
This rule is defined by the following XPath expression:
//Expression /*[self::ConditionalOrExpression or self::ConditionalAndExpression] /descendant::PrimaryExpression/PrimaryPrefix /Name[starts-with(@Image, concat(ancestor::PrimaryExpression/following-sibling::EqualityExpression [./PrimaryExpression/PrimaryPrefix/Literal/NullLiteral] /PrimaryExpression/PrimaryPrefix /Name[count(../../PrimarySuffix)=0]/@Image,".")) ]
Example:
public class Foo {
void bar() {
if (a.equals(baz) && a != null) {}
}
}
Example:
public class Foo {
void bar() {
if (a.equals(baz) || a == null) {}
}
}
Since: PMD 3.5
After checking an object reference for null, you should invoke equals() on that object rather than passing it to another object's equals() method.
This rule is defined by the following XPath expression:
//PrimarySuffix[@Image='equals' and not(../PrimaryPrefix/Literal)] /following-sibling::PrimarySuffix/Arguments/ArgumentList/Expression /PrimaryExpression[count(PrimarySuffix)=0]/PrimaryPrefix /Name[@Image = ./../../../../../../../../../../Expression/ConditionalAndExpression /EqualityExpression[@Image="!=" and count(./preceding-sibling::*)=0 and ./PrimaryExpression/PrimaryPrefix/Literal/NullLiteral] /PrimaryExpression/PrimaryPrefix/Name/@Image]
Example:
public class Test {
public String method1() { return "ok";}
public String method2() { return null;}
public void method(String a) {
String b;
/*
I don't know it method1() can be "null"
but I know "a" is not null..
I'd better write a.equals(method1())
*/
if (a!=null && method1().equals(a)) { // will
trigger the rule
//whatever
}
if (method1().equals(a) && a != null) { //
won't trigger the rule
//whatever
}
if (a!=null && method1().equals(b)) { // won't
trigger the rule
//whatever
}
if (a!=null && "LITERAL".equals(a)) { // won't
trigger the rule
//whatever
}
if (a!=null && !a.equals("go")) { // won't
trigger the rule
a=method2();
if (method1().equals(a)) {
//whatever
}
}
}
}
Since: PMD 3.6
Avoid using java.lang.ThreadGroup; although it is intended to be used in a threaded environment it contains methods that are not thread safe.
This rule is defined by the following XPath expression:
//AllocationExpression/ClassOrInterfaceType[typeof(@Image, 'java.lang.ThreadGroup')]| //PrimarySuffix[contains(@Image, 'getThreadGroup')]
Example:
public class Bar {
void buz() {
ThreadGroup tg = new ThreadGroup("My threadgroup") ;
tg = new ThreadGroup(tg, "my thread group");
tg = Thread.currentThread().getThreadGroup();
tg = System.getSecurityManager().getThreadGroup();
}
}
Since: PMD 3.8
The null check is broken since it will throw a NullPointerException itself. It is likely that you used || instead of && or vice versa.
This rule is defined by the following Java class: net.sourceforge.pmd.rules.basic.BrokenNullCheck
Example:
class Foo {
String bar(String string) {
// should be &&
if (string!=null || !string.equals(""))
return string;
// should be ||
if (string==null && string.equals(""))
return string;
}
}
Since: PMD 3.9
Don't create instances of already existing BigInteger (BigInteger.ZERO, BigInteger.ONE) and for 1.5 on, BigInteger.TEN and BigDecimal (BigDecimal.ZERO, BigDecimal.ONE, BigDecimal.TEN)
This rule is defined by the following Java class: net.sourceforge.pmd.rules.basic.BigIntegerInstantiation
Example:
public class Test {
public static void main(String[] args) {
BigInteger bi=new BigInteger(1);
BigInteger bi2=new BigInteger("0");
BigInteger bi3=new BigInteger(0.0);
BigInteger bi4;
bi4=new BigInteger(0);
}
}
Since: PMD 3.9
Integer literals should not start with zero. Zero means that the rest of literal will be interpreted as an octal value.
This rule is defined by the following Java class: net.sourceforge.pmd.rules.basic.AvoidUsingOctalValues
Example:
public class Foo {
int i = 012; // set i with 10 not 12
int j = 010; // set j with 8 not 10
k = i * j; // set k with 80 not 120
}
Since: PMD 4.1
An application with hard coded IP may become impossible to deploy in some case. It never hurts to externalize IP adresses.
This rule is defined by the following Java class: net.sourceforge.pmd.rules.basic.AvoidUsingHardCodedIP
Example:
public class Foo {
String ip = "127.0.0.1"; // This is a really bad idea !
}
This rule has the following properties:
| Name | Default value | Description |
|---|---|---|
| pattern | ^"[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}"$ | Regular Expression |
Since: PMD 4.1
Always check the return of one of the navigation method (next,previous,first,last) of a ResultSet. Indeed, if the value return is 'false', the developer should deal with it !
This rule is defined by the following XPath expression:
//Type/ReferenceType/ClassOrInterfaceType[ (@Image = 'ResultSet') and (../../../descendant::Name[ends-with(@Image,'executeQuery')]) and ( (not (contains( (./ancestor::Block/descendant::WhileStatement/descendant::Name/attribute::Image), concat(../../../VariableDeclarator/VariableDeclaratorId/attribute::Image,'.next') ) ) ) and ( not ( contains( (./ancestor::Block/descendant::IfStatement/descendant::Name/attribute::Image), concat(../../../VariableDeclarator/VariableDeclaratorId/attribute::Image,'.next') ) ) ) and (not (contains( (./ancestor::Block/descendant::WhileStatement/descendant::Name/attribute::Image), concat(../../../VariableDeclarator/VariableDeclaratorId/attribute::Image,'.previous') ) ) ) and ( not ( contains( (./ancestor::Block/descendant::IfStatement/descendant::Name/attribute::Image), concat(../../../VariableDeclarator/VariableDeclaratorId/attribute::Image,'.previous') ) ) ) and ( not ( contains( (./ancestor::Block/descendant::IfStatement/descendant::Name/attribute::Image), concat(../../../VariableDeclarator/VariableDeclaratorId/attribute::Image,'.last') ) ) ) and ( not ( contains( (./ancestor::Block/descendant::IfStatement/descendant::Name/attribute::Image), concat(../../../VariableDeclarator/VariableDeclaratorId/attribute::Image,'.first') ) ) ) ) ]
Example:
// This is NOT appropriate !
Statement stat = conn.createStatement();
ResultSet rst = stat.executeQuery("SELECT name FROM person");
rst.next(); // what if it returns a 'false' ?
String firstName = rst.getString(1);
// This is appropriate...
Statement stat = conn.createStatement();
ResultSet rst = stat.executeQuery("SELECT name FROM person");
if (rst.next())
{
String firstName = rst.getString(1);
}
else
{
// here you deal with the error ( at least log it)
}
Since: PMD 4.2
Using multiple unary operators may be a bug, and/or is confusing. Check the usage is not a bug, or consider simplifying the expression.
This rule is defined by the following XPath expression:
//UnaryExpression[ ./UnaryExpression or ./UnaryExpressionNotPlusMinus or ./PrimaryExpression/PrimaryPrefix/Expression/UnaryExpression or ./PrimaryExpression/PrimaryPrefix/Expression/UnaryExpressionNotPlusMinus ] | //UnaryExpressionNotPlusMinus[ ./UnaryExpression or ./UnaryExpressionNotPlusMinus or ./PrimaryExpression/PrimaryPrefix/Expression/UnaryExpression or ./PrimaryExpression/PrimaryPrefix/Expression/UnaryExpressionNotPlusMinus ]
Example:
// These are typo bugs, or at best needlessly complex and confusing: int i = - -1; int j = + - +1; int z = ~~2; boolean b = !!true; boolean c = !!!true; // These are better: int i = 1; int j = -1; int z = 2; boolean b = true; boolean c = false; // And these just make your brain hurt: int i = ~-2; int j = -~7;
Since: PMD 5.0
An empty initializer was found.
This rule is defined by the following XPath expression:
//Initializer/Block[count(*)=0]
Example:
public class Foo {
static {} // Why ?
{} // Again, why ?
}
Since: PMD 4.3
Explicitly calling Thread.run() method will execute in the caller's thread of control. Instead, call Thread.start() for the intended behavior.
This rule is defined by the following XPath expression:
//StatementExpression/PrimaryExpression [ PrimaryPrefix [ ./Name[ends-with(@Image, '.run') or @Image = 'run'] and substring-before(Name/@Image, '.') =//VariableDeclarator/VariableDeclaratorId/@Image [../../../Type/ReferenceType[ClassOrInterfaceType/@Image = 'Thread']] or ( ./AllocationExpression/ClassOrInterfaceType[@Image = 'Thread'] and ../PrimarySuffix[@Image = 'run']) ] ]
Example:
Thread t = new Thread(); t.run(); // use t.start() instead new Thread().run(); // same violation