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public static <T> @NonNull T @NonNull [] arrayElementsAreNonNull( @Nullable T @Nullable[] val [message #1748308]

Tue, 22 November 2016 01:21

Frank Benoit

Messages: 179
Registered: July 2009

Senior Member

How to implement a function that converts (after checks) a non-null array with all elements non-null

	public static <T> @NonNull T @NonNull [] arrayElementsAreNonNull( @Nullable T @Nullable[] value) {

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Re: public static <T> @NonNull T @NonNull [] arrayElementsAreNonNull( @Nullable T @Nullable[] [message #1748316 is a reply to message #1748308]

Tue, 22 November 2016 07:32

Frank Benoit

Messages: 179
Registered: July 2009

Senior Member

Now i have it like this, using a cast with suppressed warning.
I thougth it might be possible without this.

	
public static <T> T[] arrayIsNonNull( @Nullable T @Nullable[] value) {
	@Nullable T[] notNull = Assert.isNotNull(value);
	for( int i = 0; i < notNull.length; i++ ){
		Assert.isNotNull(notNull[i]);
	}
	@SuppressWarnings("null")
	T[] res = (@NonNull T @NonNull [])notNull;
	return res;
}

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Re: public static <T> @NonNull T @NonNull [] arrayElementsAreNonNull( @Nullable T @Nullable[] [message #1748409 is a reply to message #1748316]

Tue, 22 November 2016 20:42

Stephan Herrmann

Messages: 1853
Registered: July 2009

Senior Member

Your approach looks good, and I don't see a better alternative, because flow analysis cannot see that all array cells have been checked. After manual checks, a cast is the correct idiom for telling the compiler.

To be perfectly explicit, you may want to specify the method return type as "@NonNull T @NonNull[]", too.

BTW, feel free to open an RFE suggesting this method as an addition to our utility class org.eclipse.jdt.annotation.Checks, which already has a number of similar methods.

Stephan

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