public class EqualsAvoidNullCheck extends Check
Checks that any combination of String literals with optional assignment is on the left side of an equals() comparison.
Rationale: Calling the equals() method on String literals will avoid a potential NullPointerException. Also, it is pretty common to see null check right before equals comparisons which is not necessary in the below example. For example:
String nullString = null;
nullString.equals("My_Sweet_String");
should be refactored to
String nullString = null;
"My_Sweet_String".equals(nullString);
Limitations: If the equals method is overridden or
a covariant equals method is defined and the implementation
is incorrect (where s.equals(t) does not return the same result
as t.equals(s)) then rearranging the called on object and
parameter may have unexpected results
Java's Autoboxing feature has an affect
on how this check is implemented. Pre Java 5 all IDENT + IDENT
object concatenations would not cause a NullPointerException even
if null. Those situations could have been included in this check.
They would simply act as if they surrounded by String.valueOf()
which would concatenate the String null.
The following example will cause a NullPointerException as a result of what autoboxing does.
Integer i = null, j = null; String number = "5" number.equals(i + j);Since, it is difficult to determine what kind of Object is being concatenated all ident concatenation is considered unsafe.
| Modifier and Type | Field and Description |
|---|---|
static String |
MSG_EQUALS_AVOID_NULL
A key is pointing to the warning message text in "messages.properties"
file.
|
static String |
MSG_EQUALS_IGNORE_CASE_AVOID_NULL
A key is pointing to the warning message text in "messages.properties"
file.
|
| Constructor and Description |
|---|
EqualsAvoidNullCheck() |
| Modifier and Type | Method and Description |
|---|---|
int[] |
getAcceptableTokens()
The configurable token set.
|
int[] |
getDefaultTokens()
Returns the default token a check is interested in.
|
void |
setIgnoreEqualsIgnoreCase(boolean newValue)
Whether to ignore checking
String.equalsIgnoreCase(String). |
void |
visitToken(DetailAST methodCall)
Called to process a token.
|
beginTree, destroy, finishTree, getClassLoader, getFileContents, getLine, getLines, getRequiredTokens, getTabWidth, getTokenNames, init, isCommentNodesRequired, leaveToken, log, log, setClassLoader, setFileContents, setMessages, setTabWidth, setTokensgetCustomMessages, getId, getMessageBundle, getSeverity, getSeverityLevel, log, setId, setSeverityconfigure, contextualize, finishLocalSetup, getConfiguration, setupChildpublic static final String MSG_EQUALS_AVOID_NULL
public static final String MSG_EQUALS_IGNORE_CASE_AVOID_NULL
public int[] getDefaultTokens()
CheckgetDefaultTokens in class CheckTokenTypespublic int[] getAcceptableTokens()
CheckgetAcceptableTokens in class CheckTokenTypespublic void visitToken(DetailAST methodCall)
CheckvisitToken in class CheckmethodCall - the token to processpublic void setIgnoreEqualsIgnoreCase(boolean newValue)
String.equalsIgnoreCase(String).newValue - whether to ignore checking
String.equalsIgnoreCase(String).Copyright © 2001–2016. All rights reserved.