Code Advice #12: Use final on constructor and setter parameters

(See intro for a background and caveats on these coding advice blog entries.) In my previous code style entry I recommended a setter pattern where the parameter is identical to the field name, as in the following: void setTemperature(int temperature) { this.temperature = temperature; } I mentioned that there is the potential of a bug here if the parameter name has a typo; the code will compile just fine but not work as expected since you will be assigning the field back to itself. There is another problem that can occur when you are "masking" the field with a parameter name. What if you add some code where you don't realize that the name is referring to a parameter, not the field? If you try to update the field, you will update the parameter instead: void setTemperature(int temperature) { this.temperature = temperature; ... ... // Other code here ... if (temperature temperature = -273; } } Ooops! This motivates another good pattern (besides validating before assigning): Use the final modifier on parameters in constructors and setter methods: void setTemperature(final int temperature) { this.temperature = temperature; ... ... // Other code here ... if (temperature // Won't compile } } The final modifie...

Date: August, 08 2006
Url: http://blogs.sun.com/tor/entry/code_advice_12_use_final

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