When the same code is duplicated in two or more separate branches of a conditional, it can make the code harder to understand, maintain, and can
potentially introduce bugs if one instance of the code is changed but others are not.
Having two whens in a switch statement or two branches in an if chain with the same implementation is at
best duplicate code, and at worst a coding error.
if (a >= 0 && a < 10) {
doFirstThing();
doTheThing();
}
else if (a >= 10 && a < 20) {
doTheOtherThing();
}
else if (a >= 20 && a < 50) {
doFirstThing();
doTheThing(); // Noncompliant; duplicates first condition
}
else {
doTheRest();
}
switch on i {
when 1 {
doFirstThing();
doSomething();
}
when 2 {
doSomethingDifferent();
}
when 3 { // Noncompliant; duplicates when 1's implementation
doFirstThing();
doSomething();
}
when else {
doTheRest();
}
}
If the same logic is truly needed for both instances, then:
- in an
if chain they should be combined
if ((a >= 0 && a < 10) || (a >= 20 && a < 50)) {
doFirstThing();
doTheThing();
}
else if (a >= 10 && a < 20) {
doTheOtherThing();
}
else {
doTheRest();
}
- for a
switch, the values should be put in the when values list.
switch on i {
when 1, 3 {
doFirstThing();
doSomething();
}
when 2 {
doSomethingDifferent();
}
when else {
doTheRest();
}
}
Exceptions
Blocks in an if chain that contain a single line of code are ignored, as are blocks in a switch statement that contain a
single line of code with or without a following break.
if(a == 1) {
doSomething(); //no issue, usually this is done on purpose to increase the readability
} else if (a == 2) {
doSomethingElse();
} else {
doSomething();
}
But this exception does not apply to if chains without else-s, or to switch-es without default clauses when
all branches have the same single line of code. In the case of if chains with else-s, or of switch-es with
default clauses, rule S3923 raises a bug.
if(a == 1) {
doSomething(); //Noncompliant, this might have been done on purpose but probably not
} else if (a == 2) {
doSomething();
}
