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<h2>Unnecessary Rules ("<i>rulesets/unnecessary.xml</i>")<a name="Unnecessary_Rules_rulesetsunnecessary.xml"></a></h2><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<div class="section">
<h3><a name="AddEmptyString">AddEmptyString</a> Rule<a name="AddEmptyString_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.13</i></p>
<p>Finds empty string literals which are being added. This is an inefficient way to convert any type to a String.</p>
<p>Examples:</p>
<div>
<pre> // do not add empty strings to things
def a = '' + 123
def b = method('' + property)
// these examples are OK and do not trigger violations
def c = 456.toString()
def d = property?.toString() ?: ""
</pre></div></div>
<div class="section">
<h3><a name="ConsecutiveLiteralAppends">ConsecutiveLiteralAppends</a> Rule<a name="ConsecutiveLiteralAppends_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.13</i></p>
<p>Violations occur when method calls to append(Object) are chained together with literals as parameters. The chained calls can be joined into one invocation.</p>
<p>Example of violations:</p>
<div>
<pre> writer.append('foo').append('bar') // strings can be joined
writer.append('foo').append(5) // string and number can be joined
writer.append('Hello').append("$World") // GString can be joined
</pre></div>
<p>Example of passing code:</p>
<div>
<pre> // usage not chained invocation
writer.append('Hello')
writer.append('World')
writer.append(null).append(5) // nulls cannot be joined
writer.append().append('Hello') // no arg append is unknown
writer.append('a', 'b').append('Hello') // two arg append is unknown
</pre></div></div>
<div class="section">
<h3><a name="ConsecutiveStringConcatenation">ConsecutiveStringConcatenation</a> Rule<a name="ConsecutiveStringConcatenation_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.13</i></p>
<p>Catches concatenation of two string literals on the same line. These can safely by joined. In Java, the Java compiler will join two String literals together and place them in the Constant Pool. However, Groovy will not because the plus() method may override the + operator.</p>
<p>Examples:</p>
<div>
<pre> // Violations
def a = 'Hello' + 'World' // should be 'HelloWorld'
def b = "$Hello" + 'World' // should be "${Hello}World"
def c = 'Hello' + "$World" // should be "Hello${World}"
def d = 'Hello' + 5 // should be 'Hello5'
def e = 'Hello' + '''
world // should be joined
'''
def f = '''Hello
''' + 'world' // should be joined
// Not Violations
def g = 'Hello' + // OK because of line break
'World'
def h = 'Hello' + null // OK because not a string
def i = 'Hello' + method() // OK because not a string
def j = 'Hello' - "$World" // OK because not +
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryBigDecimalInstantiation">UnnecessaryBigDecimalInstantiation</a> Rule<a name="UnnecessaryBigDecimalInstantiation_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>It is unnecessary to instantiate <tt>BigDecimal</tt> objects. Instead just use the decimal literal or the 'G' identifier to force the type, such as <tt>123.45</tt> or <tt>123.45G</tt>.</p>
<p>This rule does not produce violations when the parameter evaluates to an integer/long, e.g. <tt>new BigDecimal(42)</tt>, <tt>new BigDecimal(42L)</tt> or <tt>new BigDecimal("42")</tt>, because using the "G" suffix on an integer value produces a <tt>BigInteger</tt>, rather than a <tt>BigDecimal</tt>, e.g. <tt>45G</tt>. So that means there is no way to produce a <tt>BigDecimal</tt> with exactly that value using a literal.</p>
<p>This rule also does not produce violations when the parameter is a double, e.g. <tt>new BigDecimal(12.3)</tt>. That scenario is covered by the <a href="./codenarc-rules-basic.html#BigDecimalInstantiation">BigDecimalInstantiation</a> rule, because that produces an unpredictable (double) value (and so it is <i>unsafe</i>, rather than <i>unnecessary</i>).</p></div>
<div class="section">
<h3><a name="UnnecessaryBigIntegerInstantiation">UnnecessaryBigIntegerInstantiation</a> Rule<a name="UnnecessaryBigIntegerInstantiation_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>It is unnecessary to instantiate <tt>BigInteger</tt> objects. Instead just use the literal with the 'G' identifier to force the type, such as <tt>8G</tt> or <tt>42G</tt>.</p></div>
<div class="section">
<h3><a name="UnnecessaryBooleanExpression">UnnecessaryBooleanExpression</a> Rule<a name="UnnecessaryBooleanExpression_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p>Checks for unnecessary boolean expressions, including ANDing (&&) or ORing (||) with <tt>true</tt>, <tt>false</tt>, <tt>null</tt>, or a Map/List/String/Number literal.</p>
<p>This rule also checks for negation (!) of <tt>true</tt>, <tt>false</tt>, <tt>null</tt>, or a Map/List/String/Number literal.</p>
<p>Examples of violations include:</p>
<div>
<pre> result = value && true // AND or OR with boolean constants
if (false || value) { .. }
return value && Boolean.FALSE
result = null && value // AND or OR with null
result = value && "abc" // AND or OR with String literal
result = value && 123 // AND or OR with Number literal
result = 678.123 || true
result = value && [x, y] // AND or OR with List literal
result = [a:123] && value // AND or OR with Map literal
result = !true // Negation of boolean constants
result = !false
result = !Boolean.TRUE
result = !null // Negation of null
result = !"abc" // Negation of String literal
result = ![a:123] // Negation of Map literal
result = ![a,b] // Negation of List literal
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryBooleanInstantiation">UnnecessaryBooleanInstantiation</a> Rule<a name="UnnecessaryBooleanInstantiation_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12 (formerly BooleanInstantiation Rule in the "basic" rule set)</i></p>
<p>Checks for direct call to a <tt>Boolean</tt> constructor. Use <tt>Boolean.valueOf()</tt> or the <tt>Boolean.TRUE</tt> and <tt>Boolean.FALSE</tt> constants instead of calling the <tt>Boolean()</tt> constructor directly.</p>
<p>Also checks for <tt>Boolean.valueOf(true)</tt> or <tt>Boolean.valueOf(false)</tt>. Use the <tt>Boolean.TRUE</tt> or <tt>Boolean.FALSE</tt> constants instead.</p>
<p>Here is an example of code that produces a violation:</p>
<div>
<pre> def b1 = new Boolean(true) // violation
def b2 = new java.lang.Boolean(false) // violation
def b3 = Boolean.valueOf(true) // violation
def b4 = Boolean.valueOf(false) // violation
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryCallForLastElement">UnnecessaryCallForLastElement</a> Rule<a name="UnnecessaryCallForLastElement_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>This rule checks for excessively verbose methods of accessing the last element of an array or list. For instance, it is possible to access the last element of an array by performing <tt>array[array.length - 1]</tt>, in Groovy it is simpler to either call <tt>array.last()</tt> or <tt>array[-1]</tt>. The same is true for lists. This violation is triggered whenever a <tt>get</tt>, <tt>getAt</tt>, or array-style access is used with an object size check.</p>
<p>Code like this all cause violations.</p>
<div>
<pre> def x = [0, 1, 2]
def a = x.get(x.size() -1)
def b = x.get(x.length -1)
def c = x.getAt(x.size() -1)
def d = x.getAt(x.length -1)
def f = x[(x.size() -1]
def d = x[(x.length -1]
</pre></div>
<p>All of this code is fine though:</p>
<div>
<pre> def x = [0, 1, 2]
def a = x.last()
def b = x[-1]
def c = x.getAt(-1)
def d = x.get(z.size() -1) // different objects
def e = x.get(z.length -1) // different objects
def f = x.getAt(z.size() -1) // different objects
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryCallToSubstring">UnnecessaryCallToSubstring</a> Rule<a name="UnnecessaryCallToSubstring_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.13</i></p>
<p>Calling String.substring(0) always returns the original string. This code is meaningless.</p>
<p>Examples:</p>
<div>
<pre> string.substring(0) // violation
method().substring(0) // violation
prop.substring(1) // OK, not constant 0
prop.substring(0, 1) // OK, end is specified
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryCast">UnnecessaryCast</a> Rule<a name="UnnecessaryCast_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.21</i></p>
<p>Checks for unnecessary cast operations.</p>
<p>Example of violations:</p>
<div>
<pre> int count = (int)123 // violation
def longValue = (long)123456L // violation
def bigDecimal = (BigDecimal)1234.56 // violation
String name = (String) "Joe" // violation
def list = (List)[1, 2, 3] // violation
def map = (Map)[a:1] // violation
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryCatchBlock">UnnecessaryCatchBlock</a> Rule<a name="UnnecessaryCatchBlock_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>Violations are triggered when a <i>catch</i> block does nothing but throw the original exception. In this scenario there is usually no need for a <i>catch</i> block, just let the exception be thrown from the original code. This condition frequently occurs when catching an exception for debugging purposes but then forgetting to take the <tt>catch</tt> statement out.</p></div>
<div class="section">
<h3><a name="UnnecessaryCollectCall">UnnecessaryCollectCall</a> Rule<a name="UnnecessaryCollectCall_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>Some method calls to <tt>Object.collect(Closure)</tt> can be replaced with the spread operator. For instance, <tt>list.collect <a name="it.multiply2"> it.multiply(2) </a></tt> can be replaced by <tt>list*.multiply(2)</tt>.</p>
<p>Examples of violations include:</p>
<div>
<pre> assert [1, 2, 3].collect { it.multiply(2) }
assert [1, 2, 3].collect { x -> x.multiply(2) }
["1", "2", "3"].collect { it.bytes }
</pre></div>
<p>The following code does not produce violations:</p>
<div>
<pre> [1, 2, 3].collect { it * it } // OK, closure parameter is referenced twice
[1, 2, 3].mapMethod { it.multiply(5) } // OK, method call is not collect
[1, 2, 3].collect(5) // OK, collect parameter is not a closure
// OK, the closure is not a simple one line statement
[1, 2, 3].collect { println it; it.multiply(5) }
// OK, closure has too many arguments
[1, 2, 3].collect { a, b -> a.multiply(b) }
// OK, closure statement references parameter multiple times
[1, 2, 3].collect { it.multiply(it) }
// OK, it is referenced several times in the closure
[1, 2, 3].collect { it.multiply(2).multiply(it) }
["1", "2", "3"].collect { it.bytes.foo(it) }
// OK, chained methods are too complex to analyze at this point
[1, 2, 3].collect { it.multiply(2).multiply(4) }
// in general the above examples can be rewritten like this:
[1, 2, 3]*.multiply(2)
["1", "2", "3"]*.bytes
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryCollectionCall">UnnecessaryCollectionCall</a> Rule<a name="UnnecessaryCollectionCall_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.11</i></p>
<p>Checks for useless calls to collections. For any collection <tt>c</tt>, calling <tt>c.containsAll(c)</tt> should always be <tt>true</tt>, and <tt>c.retainAll(c)</tt> should have no effect.</p></div>
<div class="section">
<h3><a name="UnnecessaryConstructor">UnnecessaryConstructor</a> Rule<a name="UnnecessaryConstructor_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.11</i></p>
<p>This rule detects when a constructor is not necessary; i.e., when there's only one constructor, it's <tt>public</tt>, has an empty body, and takes no arguments, or else contains only a single call to <tt>super()</tt>.</p>
<p>Example of violations:</p>
<div>
<pre> class MyClass {
public MyClass() { // violation; constructor is not necessary
}
}
class MyClass2 extends OtherClass {
MyClass2() { // violation; constructor is not necessary
super()
}
}
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryDefInFieldDeclaration">UnnecessaryDefInFieldDeclaration</a> Rule<a name="UnnecessaryDefInFieldDeclaration_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.16</i></p>
<p>If a field has a visibility modifier or a type declaration, then the def keyword is unneeded. For instance, 'static def constraints = <a name="a"></a>' is redundant and can be simplified to 'static constraints = <a name="a"></a>.</p>
<p>Example of violations:</p>
<div>
<pre> class MyClass {
// def is redundant
static def constraints = { }
// def and private is redundant
def private field1 = { }
// def and protected is redundant
def protected field2 = { }
// def and public is redundant
def public field3 = { }
// def and static is redundant
def static field4 = { }
// def and type is redundant
def Object field5 = { }
}
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryDefInMethodDeclaration">UnnecessaryDefInMethodDeclaration</a> Rule<a name="UnnecessaryDefInMethodDeclaration_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.13</i></p>
<p>If a method has a visibility modifier or a type declaration, then the def keyword is unneeded. For instance 'def private method() <a name="a"></a>' is redundant and can be simplified to 'private method() <a name="a"></a>'.</p>
<p>Examples of violations:</p>
<div>
<pre> // def and private is redundant
def private method1() { return 4 }
// def and protected is redundant
def protected method2() { return 4 }
// def and public is redundant
def public method3() { return 4 }
// def and static is redundant
def static method4() { return 4 }
// def and type is redundant
def Object method5() { return 4 }
class MyClass {
def MyClass() {} // def is redundant
}
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryDefInVariableDeclaration">UnnecessaryDefInVariableDeclaration</a> Rule<a name="UnnecessaryDefInVariableDeclaration_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.15</i></p>
<p>If a variable has a visibility modifier or a type declaration, then the def keyword is unneeded. For instance 'def private n = 2' is redundant and can be simplified to 'private n = 2'.</p>
<p>Examples of violations:</p>
<div>
<pre> // def and private is redundant
def private string1 = 'example'
// def and protected is redundant
def protected string2 = 'example'
// def and public is redundant
def public string3 = 'example'
// def and static is redundant
def static string4 = 'example'
// def and final is redundant
def final string5 = 'example'
// def and a type is redundant
def String string6 = 'example'
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryDotClass">UnnecessaryDotClass</a> Rule<a name="UnnecessaryDotClass_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.15</i></p>
<p>To make a reference to a class, it is unnecessary to specify the '.class' identifier. For instance String.class can be shortened to String.</p>
<p>Example of violations:</p>
<div>
<pre> // The '.class' identifier is unnecessary, violation occurs
def x = String.class
// Ok, unnecessary '.class' identifier has been excluded
def x = String
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryDoubleInstantiation">UnnecessaryDoubleInstantiation</a> Rule<a name="UnnecessaryDoubleInstantiation_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>It is unnecessary to instantiate <tt>Double</tt> objects. Instead just use the double literal with 'D' identifier to force the type, such as <tt>123.45d</tt> or <tt>0.42d</tt>.</p></div>
<div class="section">
<h3><a name="UnnecessaryElseStatement">UnnecessaryElseStatement</a> Rule<a name="UnnecessaryElseStatement_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.14</i></p>
<p>When an <tt>if</tt> statement block ends with a <tt>return</tt> statement, then the <tt>else</tt> is unnecessary. The logic in the <tt>else</tt> branch can be run without being in a new scope.</p>
<p>Example of violations:</p>
<div>
<pre> if(value){
println 'Executing if logic...'
return true
} else {
println 'Executing else logic...'
}
// can be replaced by:
if(value){
println 'Executing if logic...'
return true
}
println 'Executing else logic...'
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryFinalOnPrivateMethod">UnnecessaryFinalOnPrivateMethod</a> Rule<a name="UnnecessaryFinalOnPrivateMethod_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.14</i></p>
<p>A private method is marked final. Private methods cannot be overridden, so marking it final is unnecessary.</p>
<p>Example of violations:</p>
<div>
<pre> private final method() {}
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryFloatInstantiation">UnnecessaryFloatInstantiation</a> Rule<a name="UnnecessaryFloatInstantiation_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>It is unnecessary to instantiate <tt>Float</tt> objects. Instead just use the float literal with the 'F' identifier to force the type, such as <tt>123.45F</tt> or <tt>0.42f</tt>.</p></div>
<div class="section">
<h3><a name="UnnecessaryGetter">UnnecessaryGetter</a> Rule<a name="UnnecessaryGetter_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>Checks for explicit calls to getter/accessor methods which can, for the most part, be replaced by property access. A getter is defined as a method call that matches <tt>get[A-Z]</tt> but not <tt>getClass()</tt> or <tt>get[A-Z][A-Z]</tt> such as <tt>getURL()</tt>. Getters do not take method arguments.</p>
<p>These bits of code produce violations:</p>
<div>
<pre> x.getProperty()
x.getFirst()
x.getFirstName()
x.getA()
</pre></div>
<p>These bits of code do not:</p>
<div>
<pre> x.property
x.first
x.firstName
x.a
x.getURL()
x.getClass()
x.getProperty('key')
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryGString">UnnecessaryGString</a> Rule<a name="UnnecessaryGString_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.13</i></p>
<p>String objects should be created with single quotes, and GString objects created with double quotes. Creating normal String objects with double quotes is confusing to readers.</p>
<p>Example of violations:</p>
<div>
<pre> def a = "I am a string" // violation
// violation
def b = """
I am a string
"""
def c = "I am a ' string" // OK
def d = """I am a ' string""" // OK
def e = """I am a ' string""" // OK
def f = "I am a \$ string" // OK
// OK
def g = """
I am a \$ string
"""
// OK
def h = """
I am a $string
"""
def i = 'i am a string'
def j = '''i am a
string
'''
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryIfStatement">UnnecessaryIfStatement</a> Rule<a name="UnnecessaryIfStatement_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p>Checks for unnecessary <b>if</b> statements. The entire <b>if</b> statement, or at least the <i>if</i> or <i>else</i> block, are considered unnecessary for the four scenarios described below.</p>
<p>(1) When the <i>if</i> and <i>else</i> blocks contain only an explicit return of <tt>true</tt> and <tt>false</tt> constants. These cases can be replaced by a simple <i>return</i> statement. Examples of violations include:</p>
<div>
<pre> if (someExpression) // can be replaced by: return someExpression
return true
else
return false
if (someExpression) { // can be replaced by: return !someExpression
return false
} else {
return true
}
if (someExpression) { // can be replaced by: return someExpression
return Boolean.TRUE
} else {
return Boolean.FALSE
}
</pre></div>
<p>(2) When the <tt>if</tt> statement is the last statement in a block and the <i>if</i> and <i>else</i> blocks are only <tt>true</tt> and <tt>false</tt> expressions. This is an <i>implicit</i> return of <tt>true</tt>/<tt>false</tt>. For example, the <tt>if</tt> statement in the following code can be replaced by <tt>someExpression</tt> or <tt>someExpression as boolean</tt>:</p>
<div>
<pre> def myMethod() {
doSomething()
if (someExpression)
true
else false
}
</pre></div>
<p>(3) When the second-to-last statement in a block is an <tt>if</tt> statement with no <tt>else</tt>, where the block contains a single <tt>return</tt> statement, and the last statement in the block is a <tt>return</tt> statement, and one <tt>return</tt> statement returns a <tt>true</tt> expression and the other returns a <tt>false</tt> expression. This check is disabled by setting <tt>checkLastStatementImplicitElse</tt> to <tt>false</tt>. For example, the <tt>if</tt> statement in the following code can be replaced by <tt>return expression1</tt>:</p>
<div>
<pre> def myMethod() {
doSomething()
if (expression1) {
return true
}
return false
}
</pre></div>
<p>(4) When either the <i>if</i> block or <i>else</i> block of an <tt>if</tt> statement that is not the last statement in a block contain only a single constant or literal expression. For example, the <tt>if</tt> statement in the following code has no effect and can be removed:</p>
<div>
<pre> def myMethod() {
if (someExpression) { 123 }
doSomething()
}
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryInstanceOfCheck">UnnecessaryInstanceOfCheck</a> Rule<a name="UnnecessaryInstanceOfCheck_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.15</i></p>
<p>This rule finds instanceof checks that cannot possibly evaluate to true. For instance, checking that <tt>(!variable instanceof String)</tt> will never be true because the result of a not expression is always a boolean.</p>
<p>Example of violations:</p>
<div>
<pre> if (!variable instanceof String) { ... } // always false
def x = !variable instanceof String // always false
if (!variable instanceof Boolean) { ... } // always true
def x = !variable instanceof Boolean // always true
// this code is OK
if (!(variable instanceof String)) { ... }
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryInstantiationToGetClass">UnnecessaryInstantiationToGetClass</a> Rule<a name="UnnecessaryInstantiationToGetClass_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since in CodeNarc 0.12</i></p>
<p>Avoid instantiating an object just to call getClass() on it; use the .class public member instead.</p>
<div>
<pre> public class Foo {
// Replace this
Class c = new String().getClass();
// with this:
Class c = String.class;
}
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryIntegerInstantiation">UnnecessaryIntegerInstantiation</a> Rule<a name="UnnecessaryIntegerInstantiation_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>It is unnecessary to instantiate <tt>Integer</tt> objects. Instead just use the literal with the 'I' identifier to force the type, such as <tt>8I</tt> or <tt>42i</tt>.</p></div>
<div class="section">
<h3><a name="UnnecessaryLongInstantiation">UnnecessaryLongInstantiation</a> Rule<a name="UnnecessaryLongInstantiation_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>It is unnecessary to instantiate <tt>Long</tt> objects. Instead just use the literal with the 'L' identifier to force the type, such as <tt>8L</tt> or <tt>42L</tt>.</p></div>
<div class="section">
<h3><a name="UnnecessaryModOne">UnnecessaryModOne</a> Rule<a name="UnnecessaryModOne_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.13</i></p>
<p>Any expression mod 1 (exp % 1) is guaranteed to always return zero. This code is probably an error, and should be either (exp & 1) or (exp % 2).</p>
<p>Examples:</p>
<div>
<pre> if (exp % 1) {} // violation
if (method() % 1) {} // violation
if (exp & 1) {} // ok
if (exp % 2) {} // ok
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryObjectReferences">UnnecessaryObjectReferences</a> Rule<a name="UnnecessaryObjectReferences_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>Violations are triggered when an excessive set of consecutive statements all reference the same variable. This can be made more readable by using a <tt>with</tt> or <tt>identity</tt> block. By default, 5 references are allowed. You can override this property using the <b>maxReferencesAllowed</b>> property on the rule.</p>
<p>These two bits of code produce violations:</p>
<div>
<pre> def p1 = new Person()
p1.firstName = 'Hamlet'
p1.lastName = "D'Arcy"
p1.employer = 'Canoo'
p1.street = 'Kirschgaraten 5'
p1.city = 'Basel'
p1.zipCode = '4051'
def p2 = new Person()
p2.setFirstName('Hamlet')
p2.setLastName("D'Arcy")
p2.setEmployer('Canoo')
p2.setStreet('Kirschgaraten 5')
p2.setCity('Basel')
p2.setZipCode('4051')
</pre></div>
<p>However, these two bits of code do not because they use either a <tt>with</tt> or <tt>identity</tt> block.</p>
<div>
<pre> def p1 = new Person().with {
firstName = 'Hamlet'
lastName = "D'Arcy"
employer = 'Canoo'
street = 'Kirschgaraten 5'
city = 'Basel'
zipCode = '4051'
}
def p2 = new Person().identity {
firstName = 'Hamlet'
lastName = "D'Arcy"
employer = 'Canoo'
street = 'Kirschgaraten 5'
city = 'Basel'
zipCode = '4051'
}
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryNullCheck">UnnecessaryNullCheck</a> Rule<a name="UnnecessaryNullCheck_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>Groovy contains the safe dereference operator. It can be used in boolean conditional statements to safely replace explicit <tt>x == null</tt> tests. Also, testing the 'this' or 'super' reference for null equality is pointless and can be removed.</p>
<p>Examples of violations:</p>
<div>
<pre> if (obj != null && obj.method()) { }
if (obj != null && obj.prop) { }
// this is pointless and won't avoid NullPointerException
if (obj.method() && obj != null ) { }
if (this == null) { }
if (null == this) { }
if (this != null) { }
if (null != this) { }
if (super == null) { }
if (null == super) { }
if (super != null) { }
if (null != super) { }
</pre></div>
<p>Examples of acceptable code:</p>
<div>
<pre> // null check it OK
if (obj != null) { }
// null safe dereference in if is OK
if (obj?.method()) { }
// null safe dereference in ternary is OK
(obj?.prop && obj?.prop2) ? x : y
// obj is reused in a parameter list, so OK
if (obj != null && obj.method() && isValid(obj)) { }
// rule is not so complex yet...
(obj != null && obj.prop && obj.method()) ? x : y
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryNullCheckBeforeInstanceOf">UnnecessaryNullCheckBeforeInstanceOf</a> Rule<a name="UnnecessaryNullCheckBeforeInstanceOf_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12</i></p>
<p>There is no need to check for null before an instanceof; the instanceof keyword returns false when given a null argument.</p>
<p>Example:</p>
<div>
<pre> if (x != null && x instanceof MyClass) {
// should drop the "x != null" check
}
if (x instanceof MyClass && x != null) {
// should drop the "x != null" check
}
// should drop the "x != null" check
(x != null && x instanceof MyClass) ? foo : bar
if (x != null && x instanceof MyClass && x.isValid()) {
// this is OK and causes no violation because the x.isValid() requires a non null reference
}
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryOverridingMethod">UnnecessaryOverridingMethod</a> Rule<a name="UnnecessaryOverridingMethod_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.11</i></p>
<p>Checks for an overriding method that merely calls the same method defined in a superclass. Remove it.</p></div>
<div class="section">
<h3><a name="UnnecessaryPackageReference">UnnecessaryPackageReference</a> Rule<a name="UnnecessaryPackageReference_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.14</i></p>
<p>Checks for explicit package reference for classes that Groovy imports by default, such as <tt>java.lang.String</tt>, <tt>java.util.Map</tt> and <tt>groovy.lang.Closure</tt>, as well as classes that were explicitly imported.</p>
<p>You do not need to specify the package for any classes from <i>java.lang</i>, <i>java.util</i>, <i>java.io</i>, <i>java.net</i>, <i>groovy.lang</i> and <i>groovy.util</i>, as well as the classes <i>java.math.BigDecimal</i> and <i>java.math.BigInteger</i>.</p>
<p>Examples of violations include:</p>
<div>
<pre> // Field types
class MyClass {
java.math.BigDecimal amount = 42.10 // violation
}
// Within expressions
if (value.class == java.math.BigInteger) { } // violation
println "isClosure=${v instanceof groovy.lang.Closure}" // violation
def p = java.lang.Runtime.availableProcessors() // violation
// Constructor calls
def url = new java.net.URL('http://abc@example.com') // violation
// Variable types
void doSomething() {
java.math.BigInteger maxValue = 0 // violation
java.net.URI uri // violation
}
// Method return types
java.io.Reader getReader() { } // violation
groovy.util.AntBuilder getAntBuilder() { } // violation
// Method parameter types
void writeCount(java.io.Writer writer, int count) { } // violation
void init(String name, groovy.lang.Binding binding) { } // violation
// Closure parameter types
def writeCount = { java.io.Writer writer, int count -> } // violation
// Extends and implements
class MyHashMap extends java.util.HashMap { } // violation
class MyList implements java.util.List { } // violation
// Explicitly imported classes
import javax.servlet.http.Cookie
import javax.sql.DataSource
class MyClass {
void doStuff(javax.servlet.http.Cookie cookie) { // violation
def dataSource = [:] as javax.sql.DataSource // violation
}
}
</pre></div>
<p>Known limitations:</p>
<ul>
<li>Does not catch class declarations that explicitly extend <tt>java.lang.Object</tt>. For instance, <tt>class MyClass extends java.lang.Object <a name="a"> </a></tt>. Just don't do that, okay?</li>
<li>Does not catch class declarations that explicitly extend <tt>groovy.lang.Script</tt>. For instance, <tt>class MyScript extends groovy.lang.Script<a name="a"> </a></tt>. Don't do that, either!</li>
<li>Does not catch unnecessary package references if they are the types of anonymous inner class definitions, for older versions of Groovy (<i> 1.7.10?). For instance, <<<def runnable = new java.lang.Runnable() <a name="a..."> ... </a></i>>>.</li></ul></div>
<div class="section">
<h3><a name="UnnecessaryParenthesesForMethodCallWithClosure">UnnecessaryParenthesesForMethodCallWithClosure</a> Rule<a name="UnnecessaryParenthesesForMethodCallWithClosure_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.14</i></p>
<p>If a method is called and the only parameter to that method is an inline closure then the parentheses of the method call can be omitted.</p>
<p>Example of violations:</p>
<div>
<pre> [1,2,3].each() { println it }
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryPublicModifier">UnnecessaryPublicModifier</a> Rule<a name="UnnecessaryPublicModifier_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.13</i></p>
<p>The 'public' modifier is not required on methods, constructors or classes.</p>
<p>Example of violations:</p>
<div>
<pre> // violation on class
public class MyClass {
// violation on constructor
public MyClass() {}
// violation on method
public void myMethod() {}
}
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryReturnKeyword">UnnecessaryReturnKeyword</a> Rule<a name="UnnecessaryReturnKeyword_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.11</i></p>
<p>In Groovy, the <tt>return</tt> keyword is often optional. If a statement is the last line in a method or closure then you do not need to have the <tt>return</tt> keyword.</p></div>
<div class="section">
<h3><a name="UnnecessarySafeNavigationOperator">UnnecessarySafeNavigationOperator</a> Rule<a name="UnnecessarySafeNavigationOperator_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.22</i></p>
<p>Check for the <i>safe navigation</i> operator (<tt>?.</tt>) applied to constants and literals, or <tt>this</tt> or <tt>super</tt>, or constructor calls, all of which can never be null.</p>
<p>Example of violations:</p>
<div>
<pre> def myMethod() {
"abc"?.bytes // violation
[1,2]?.getSize() // violation
[abc:123]?.name // violation
[:]?.toString() // violation
123?.class // violation
123.45?.getClass() // violation
Boolean.FALSE?.class // violation
Boolean.TRUE?.class // violation
this?.class // violation
super?.getClass() // violation
new Long(100)?.class // violation
}
</pre></div></div>
<div class="section">
<h3><a name="UnnecessarySelfAssignment">UnnecessarySelfAssignment</a> Rule<a name="UnnecessarySelfAssignment_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.13</i></p>
<p>Method contains a pointless self-assignment to a variable or property. Either the code is pointless or the equals()/get() method has been overridden to have a side effect, which is a terrible way to code getters and violates the contract of equals().</p>
<p>Examples:</p>
<div>
<pre> x = x // violation
def method(y) {
y = y // violation
}
a.b.c = a.b.c // violation
x = y // acceptable
a.b = a.zz // acceptable
a.b = a().b // acceptable
</pre></div></div>
<div class="section">
<h3><a name="UnnecessarySemicolon">UnnecessarySemicolon</a> Rule<a name="UnnecessarySemicolon_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.13</i></p>
<p>Semicolons as line terminators are not required in Groovy: remove them. Do not use a semicolon as a replacement for empty braces on for and while loops; this is a confusing practice.</p>
<p>The rule contains a String property called 'excludePattern'. Any source code line matching this pattern will not trigger a violation. The default value is '\s?\*.*|/\*.*|.*//.*|.*\*/.*' This is to filter out comments. Any source line that even looks like it is a comment is ignored.</p>
<p>\s?*.* == whitespace plus star character plus anything /*.* == any line that contains the /* sequence .*//.* == any line that contains the // sequence .**/.* == any line that contains the */ sequence</p>
<p>Example of violations:</p>
<div>
<pre> package my.company.server; // violation
import java.lang.String; // violation
println(value) ; // violation
for (def x : list); // violation
// this code is OK
println(value); println (otherValue)
</pre></div></div>
<div class="section">
<h3><a name="UnnecessarySubstring">UnnecessarySubstring</a> Rule<a name="UnnecessarySubstring_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.15</i></p>
<p>This rule finds usages of <tt>String.substring(int)</tt> and <tt>String.substring(int, int)</tt> that can be replaced by use of the subscript operator. For instance, <tt>var.substring(5)</tt> can be replaced with <tt>var[5..-1]</tt>.</p>
<p>Note that the String.substring(beginIndex,endIndex) method specifies a range of beginIndex..endIndex-1, while Groovy's String subscript specifies an inclusive range. So, <tt>"123456".substring(1, 5)</tt> is equivalent to <tt>"123456"[1..4]</tt>.</p>
<p>Example of violations:</p>
<div>
<pre> myVar.substring(5) // can use myVar[5..-1] instead
myVar.substring(1, 5) // can use myVar[1..4] instead
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryStringInstantiation">UnnecessaryStringInstantiation</a> Rule<a name="UnnecessaryStringInstantiation_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.12 (formerly StringInstantiation Rule in the "basic" rule set)</i></p>
<p>Checks for direct call to the <tt>String</tt> constructor that accepts a <tt>String</tt> literal. In almost all cases, this is unnecessary. Use a <tt>String</tt> literal (e.g., "...") instead of calling the corresponding <tt>String</tt> constructor (<tt>new String("..")</tt>) directly.</p>
<p>Here is an example of code that produces a violation:</p>
<div>
<pre> def s = new String('abc')
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryTernaryExpression">UnnecessaryTernaryExpression</a> Rule<a name="UnnecessaryTernaryExpression_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p>Checks for ternary expressions where the conditional expression always evaluates to a boolean and the <i>true</i> and <i>false</i> expressions are merely returning <tt>true</tt> and <tt>false</tt> constants. These cases can be replaced by a simple boolean expression. Examples of violations include:</p>
<div>
<pre> x==99 ? true : false // can be replaced by: x==99
x && y ? true : false // can be replaced by: x && y
x||y ? false : true // can be replaced by: !(x||y)
x >= 1 ? true: false // can be replaced by: x >= 1
x < 99 ? Boolean.TRUE : Boolean.FALSE // can be replaced by: x < 99
!x ? true : false // can be replaced by: !x
</pre></div>
<p>The rule also checks for ternary expressions where the <i>true</i> and <i>false</i> expressions are the same constant or variable. Examples include:</p>
<div>
<pre> x ? '123' : '123' // can be replaced by: '123'
x ? null : null // can be replaced by: null
x ? 23 : 23 // can be replaced by: 23
x ? MAX_VALUE : MAX_VALUE // can be replaced by: MAX_VALUE
ready ? minValue : minValue // can be replaced by: minValue
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryTransientModifier">UnnecessaryTransientModifier</a> Rule<a name="UnnecessaryTransientModifier_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>New in CodeNarc 0.13</i></p>
<p>The field is marked as transient, but the class isn't Serializable, so marking it as transient has no effect. This may be leftover marking from a previous version of the code in which the class was transient, or it may indicate a misunderstanding of how serialization works.</p>
<p>Some Java frameworks change the semantics of the transient keyword. For instance, when using Terracotta the transient keyword may have slightly different semantics. You may need to turn this rule off depending on which Java frameworks are in use.</p>
<p>Examples:</p>
<div>
<pre> class MyClass {
// class not serializable, violation occurs
transient String property
}
class MySerializableClass implements Serializable {
// OK, class is serializable
transient String property
}
</pre></div></div>
<div class="section">
<h3><a name="UnnecessaryToString">UnnecessaryToString</a> Rule<a name="UnnecessaryToString_Rule"></a></h3><!-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
<p><i>Since CodeNarc 0.21</i></p>
<p>Checks for unnecessary calls to <tt>toString()</tt>. This includes:</p>
<ul>
<li>Calls to <tt>toString()</tt> on a String literal or expression</li>
<li>Calls to <tt>toString()</tt> for the value assigned to a <tt>String</tt> field or variable (if <i>checkAssignments</i> is <tt>true</tt>).</li></ul>
<table border="1" class="bodyTable">
<tr class="a">
<td align="left"><b>Property</b></td>
<td align="left"><b>Description</b></td>
<td align="left"><b>Default Value</b></td></tr>
<tr class="b">
<td align="left">checkAssignments</td>
<td align="left">If <tt>true</tt>, then check for calls to <tt>toString()</tt> for the value assigned to a <tt>String</tt> field or variable.</td>
<td align="left"><tt>true</tt></td></tr></table>
<p>Example of violations:</p>
<div>
<pre> def name = "Joe".toString() // violation - string literal
def groupId = ((String)row.get('GroupID')).toString() // violation - string expression
class MyClass {
String name = nameNode.toString() // violation - field
String code = account.getCode().toString() // violation - field
void run() {
String name = nameNode.toString() // violation - variable
String id = account.id.toString() // violation - variable
}
}
</pre></div></div></div>
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