PMD Java – Unnecessary

UnnecessaryConversionTemporary

Since: PMD 0.1

Priority: 3

Avoid the use temporary objects when converting primitives to Strings. Use the static conversion methods on the wrapper classes instead.

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

Example(s):

  
public String convert(int x) {
	String foo = new Integer(x).toString();	// this wastes an object
	
	return Integer.toString(x);				// preferred approach
}

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.

UnnecessaryReturn

Since: PMD 1.3

Priority: 3

Avoid the use of unnecessary return statements.

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

Example(s):

		
public class Foo {
  public void bar() {
    int x = 42;
    return;
  }
}

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.

UnnecessaryFinalModifier

Since: PMD 3.0

Priority: 3

When a class has the final modifier, all the methods are automatically final and do not need to be tagged as such.

    
//ClassOrInterfaceDeclaration[@Final='true' and @Interface='false']
/ClassOrInterfaceBody/ClassOrInterfaceBodyDeclaration/MethodDeclaration[@Final='true']

Example(s):


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() {
    }
}

UselessOverridingMethod

Since: PMD 3.3

Priority: 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.lang.java.rule.unnecessary.UselessOverridingMethodRule

Example(s):

public void foo(String bar) {
  super.foo(bar);      // why bother overriding?
}

public String foo() {
	return super.foo();  // why bother overriding?
}

@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
violationSuppressRegex		Suppress violations with messages matching a regular expression
violationSuppressXPath		Suppress violations on nodes which match a given relative XPath expression.
ignoreAnnotations	false	Ignore annotations

UselessOperationOnImmutable

Since: PMD 3.5

Priority: 3

An operation on an Immutable object (String, BigDecimal or BigInteger) won’t change the object itself since 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.lang.java.rule.unnecessary.UselessOperationOnImmutableRule

Example(s):

    
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
  }
}

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.

UnusedNullCheckInEquals

Since: PMD 3.5

Priority: 3

After checking an object reference for null, you should invoke equals() on that object rather than passing it to another object’s equals() method.

        
(//PrimaryPrefix[ends-with(Name/@Image, '.equals') and Name/@Image != 'Arrays.equals'] | //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(s):

		
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
	}
  }
}
}

UselessParentheses

Since: PMD 5.0

Priority: 4

Useless parentheses should be removed.

          
//Expression/PrimaryExpression/PrimaryPrefix/Expression
[count(*)=1][count(./CastExpression)=0][count(./ConditionalExpression[@Ternary='true'])=0]
[not(./AdditiveExpression[//Literal[@StringLiteral='true']])]
|
//Expression/ConditionalAndExpression/PrimaryExpression/PrimaryPrefix/Expression[
    count(*)=1 and
    count(./CastExpression)=0 and
    count(./EqualityExpression/MultiplicativeExpression)=0 and
    count(./ConditionalOrExpression)=0]
|
//Expression/ConditionalOrExpression/PrimaryExpression/PrimaryPrefix/Expression[
    count(*)=1 and
    count(./CastExpression)=0 and
    count(./EqualityExpression/MultiplicativeExpression)=0]
|
//Expression/ConditionalExpression/PrimaryExpression/PrimaryPrefix/Expression[
    count(*)=1 and
    count(./CastExpression)=0 and
    count(./EqualityExpression)=0]
|
//Expression/AdditiveExpression[not(./PrimaryExpression/PrimaryPrefix/Literal[@StringLiteral = 'true'])]/PrimaryExpression[1]/PrimaryPrefix/Expression[
    count(*)=1 and
    not(./CastExpression) and
    not(./ConditionalExpression) and
    not(./ShiftExpression)]
|
//Expression/EqualityExpression/PrimaryExpression/PrimaryPrefix/Expression[
    count(*)=1 and
    count(./CastExpression)=0 and
    count(./AndExpression)=0 and
    count(./InclusiveOrExpression)=0 and
    count(./ExclusiveOrExpression)=0 and
    count(./ConditionalAndExpression)=0 and
    count(./ConditionalOrExpression)=0]

Example(s):

    
public class Foo {

   private int _bar1;
   private Integer _bar2;

   public void setBar(int n) {
      _bar1 = Integer.valueOf((n)); // here
      _bar2 = (n); // and here
   }

}