IssueTracker

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# Description:
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Javax package contains "@ParametersAreNonnullByDefault" that can be used to force "@Nonnull" by default. To achieve cleaner implementation code and to do this in Android, can we add a "@ParametersAreNonNullByDefault"? This way developers do not have to specify both "@Nullable" and "@NonNull". We can assume "@NonNull" and only specify "@Nullable" when needed if they choose to.


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# Examples:
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For Example:

@NonNull
public String someMethod(@Nullable String input) {
    return "" + input;
}

Can be written as:

public String someMethod(@Nullable String input) {
    return "" + input;
}

Since there is an empty String that "input" is appending to, this will always be non-null regardless of the String input.


A common Android example would be the following from Fragments:

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup parent, @Nullable Bundle savedInstanceState) {
    return inflater.inflate(R.layout.main_fragment, parent, false);
}

Can be written as:

@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup parent, @Nullable Bundle savedInstanceState) {
    return inflater.inflate(R.layout.main_fragment, parent, false);
}

Since we are inflating a View, as long as "main_fragment" exists in the code base, this will return a non-null View. If this method fails to inflate the layout, it will throw an "InflateException". For "inflater" variable, this is annotated as "@NonNull" and so we can drop the inherited annotation for cleanliness. Since we know both "parent" and "savedInstanceState" variables are labeled as "@Nullable", we can simply keep these to let the developers know these can potentially be "null" before using them.


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# Annotation should be added in:
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androidx.annotation:annotation:x.x.x


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# Documentation:
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https://static.javadoc.io/com.google.code.findbugs/jsr305/3.0.1/javax/annotation/ParametersAreNonnullByDefault.html


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# References:
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https://medium.com/square-corner-blog/non-null-is-the-default-58ffc0bb9111
https://github.com/square/retrofit/blob/master/retrofit/src/main/java/retrofit2/internal/EverythingIsNonNull.java