IntelliJ IDEA: Boolean method XX is always inverted

Question

I am getting warning " Boolean method is always inverted " on running lint in IntelliJ. I have several similar warnings in my codebase. Which basic coding style, am I missing?

public static boolean isBlueToothEnabled(){     final BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();     if(bluetoothAdapter != null)         return bluetoothAdapter.isEnabled();     return  false; } 

Answer 1

try to return false if bluetoothAdapter is null otherwise return the output of isEnabled()

public static boolean isBlueToothEnabled(){     final BluetoothAdapter bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();     if(bluetoothAdapter == null){         return false;     }     return bluetoothAdapter.isEnabled(); } 

Read more:

In Clean Code, Robert Martin writes, “Negatives are just a bit harder to understand than positives. So, when possible, conditionals should be expressed as positives.” (Martin, [G29]). IntelliJ IDEA has three inspections to help you stay positive.

https://blog.jetbrains.com/idea/2014/09/the-inspection-connection-issue-2/ (Entry #4 Avoiding negative Conditionals)

https://www.jetbrains.com/help/idea/2016.1/invert-boolean.html

Answer 2

Summary: Method always called like !method(). It's more efficient to have less number of computation. Refactor the method and return oppositely and call the method without (!)

---

Why it happens

If we have a method foo()

    boolean foo()     {         if(condition == true)             return true;         else             return false;     } 

And is only called like !foo(),

    class A     {         if(!foo())             do something;         ...         if(!foo())             do something else;     } 

Because we only call !foo() and did not call foo().

The warning asks us to use foo() in a positive way.

Remove the warning

By inverting the return value of the method foo(),

    boolean foo()     {         if(condition == true)             return **false**;         else             return **true**;     } 

Now call the method

    class A     {         if(foo())             do the same thing;     }