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Hi there non-structured a simple advice from Effective Java hit the item say is that if your method

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returns a collection ordinary and if the method does not have anything written then it triggered then

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an empty collection on an empty array but not a null value.

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For instance let's consider this code fragment.

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Let's assume that this method.

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So just for titles given the author mean he takes an array of the book titles.

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Now as you can see it fetches the data from the database by walking a similar method in the Davola.

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Now if not books were fun then this method returns a null value.

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And this kind of practice is already common knowledge say that this is the client code that is invoking

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ometer.

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Once that bind gets done.

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It performs a null check and only if this check succeeds it will check if the R.A.F. titles contain

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some target data.

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Now the problem with this implementation is that book client as well as the method have to write some

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external court as emphasized here in Redfern Now that this sort of implementation there is a chance

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that the client programmer might sometimes forget to perform the null check and there is a possibility

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that this would not have any effect for a long long time.

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But whenever a null is return we of course would end up with a null pointer exception.

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So the advice from this idea is to return an empty array or an empty collection then a valid argument

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would be that wouldn't it be expensive to create an empty array or an empty collection every single

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time the search fails.

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There is no date.

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I found this the counter argument is that just do not worry about performance for this sort of thing

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unless you're really sure that retaining an empty array on an empty collection is the real source of

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your performance problem.

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Your profiler would indicate that.

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So this item from effective Djala wants us not to optimize every single thing it instead advises us

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to write good programs with just good design principles like information hiding.

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Now once the design is good improving speed is a lot easier to do.

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Take a look at this item.

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I can 55 which a simple and includes some very popular software engineering quotations.

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But if performance is an issue you can still return the same instance of an employee a or the same instance

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of an empty collection.

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That is you do not have to create a new empty object.

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Each single time and there are some idioms for doing it.

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And here is an idiom for returning the same empty array for my collection here we are creating an empty

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are the only ones outside of them added on within the method.

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Once we get the list of titles from there it is.

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We simply invoke the two or method to return an array of items.

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You may recall that two array is from the collection interface.

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That is what you would use to convert a collection into an art.

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You would use Oslo's method from the collections class to convert an arcane playlist.

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Right we saw that in the collections.

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I'm not here.

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If some titled softphone then the method would internally create a new array and would fill it with

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that items and would return that ID.

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But if not items are found then the two are method.

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In this particular case I would simply return the input MTI And as mentioned earlier that input empty

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array is created only once as it is defined as static and Feinman.

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Generally if the collection has some data then the method always returns the input with the data.

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If the input array size is at least as large as the collection size.

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Only if that is not the case.

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It would create a new ID.

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And here is the idiom for always returning the same M-B immutable collection we affecting the list of

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titles from that database.

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And if this list is empty then we simply invoke the method empty list in the Collections class Collections

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class would ensure that it would always return the same empty list instance which is immutable.

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That is you cannot add anything to the return list earlier in the collections demo.

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I mentioned about the methods starting with the method name empty and also said that they will look

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at them and this lesson so empty This is one of them and there are also other similar methods like.

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Empty Set an empty map.

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Also when it comes to checking whether a collection is empty or not.

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Use the easy empty method as we see here.

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As opposed to invoking the seismometer uncompelling read 0 ism B is much more readable and it also internally

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in the size method and makes it a similar comparison.

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So that's about it.

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If your method returns either an array or collection rate under MP motions rather than returning a null

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value when there is no date to return.

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Thank you