resources.report.rules.pmd.UnusedNullCheckInEquals.html Maven / Gradle / Ivy

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UnusedNullCheckInEquals


UnusedNullCheckInEquals
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)]
 /../PrimarySuffix/Arguments/ArgumentList/Expression
 /PrimaryExpression/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
}
}
}
}