clone does not invoke super.clone()
34 }
35
36 @Override
37 public ConfigData clone() {38 ConfigData data = new ConfigData();39 data.setParams(params);4041 return data;42 }43
44 @Override
45 public boolean equals(Object o) { // JAVA-E0110
Description
Non-final class defines a clone method that does not call super.clone.
Bad Practice
class T implements Cloneable {
@Override
public Object clone() {
// Does not call super.clone();
T newObj = new T(...);
// ...
return newObj;
}
}
// ...
class U extends T implements Cloneable {
@Override
public Object clone() {
U newObj = (U)super.clone(); // This is an object of type T! This cast will fail with a ClassCastException.
// ...
return newObj;
}
}
If T is extended by a subclass U, and U calls super.clone, then it is likely that U's clone method will get an object of type T. This will likely fail within the clone method itself when the subclass modifies data. Such code violates the standard contract for clone as stated by the JavaDocs:
By convention, the returned object should be obtained by calling
super.clone. If a class and all of its superclasses (exceptObject) obey this convention, it will be the case thatx.clone().getClass() == x.getClass().
Recommended
Always make sure to call super.clone when implementing Cloneable for any class.
class T implements Cloneable {
@Override
public Object clone() {
try {
T newObj = super.clone();
// ...
return newObj;
} catch (CloneNotSupportedException e) {
// ...
}
}
}
References
- Spotbugs - CN_IDIOM_NO_SUPER_CALL