Yes, I'm doing everything in eclipse. Or Make a new class with the same code and then put your debug point after this line. Add a comment. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog.
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Please enter a valid phone number. The single most important reason is that null is the do not know equivalent of any reference type, including framework types. This implies that null cannot be replaced in any case by a more fluent version of the nothing value. So, lets say you store the Integers 1, 3, 7 in your arraylist at its corresponding index: Due to some computation, you want to get the element at index 5, so what your array should return is: "no value stored". This could be achieved through returning null or a NullObject.
In most cases returning the built in null value is expressive enough. After calling a method that can return null and using its return value a check of the returned value against null is quite common in modern code.
It is likewise useful to have a collection of files, some of which may be null. The usefulness of collections that may contain null objects proceeds directly from the usefulness of objects that may be null. It is really as simple as that. It is easier to accept everything, than to be to be restrictive and then try opening up your design after the fact. How would you do it? You would probably have to create an entirely different object, you couldn't use extend the NonNullableArrayList.
Instead if you have a ArrayList that takes everything, you could easily extend it, and override the add, where it doesn't accept null values. Very much so when you go with a List of Lists to model a 2D real life plate with different positions. Half of those positions could be empty in random coordinates while the filled ones don't represent a simple int or String but are represented by a complex object. If you want to keep the positional info, you need to fill the empty spots with null so that your list.
To counter the null exceptions you can check for null very popular or you can use an Optional which I find handy in this case. The alternative would be to fill the empty spots with "junk" objects which can lead to all kinds of mess down the road.
If your null check fails or is forgotten somewhere, Java will let you know. On the other hand a "junk" placeholder object which is not checked properly may pass unnoticed. Sign up to join this community.
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ArrayList allow to add null? Ask Question. Asked 9 years, 4 months ago. Active 2 years, 3 months ago. Viewed k times. Improve this question. DontDivideByZero 4 4 bronze badges. Alfredo Osorio Alfredo Osorio 1 1 gold badge 11 11 silver badges 18 18 bronze badges.
The Guava Project has a pretty interesting page on that topic they don't allow null in most of their collections. I believe that the answers given here cover well the question. Maybe one thing that should be mentioned is: don't take everything that's in the JDK as holly and perfect, and then whack your head trying to understand why it is so "perfect".
Some things are honest, IMHO mistakes, that remained there due to backwards compatibility and that's that. At any rate, your question comes down to weather there isn't a more elegant way to catch NPE in Java. The answer is, no, but there should be.
Can you provide more information on why it should not be allowed? If it is just a matter of taste, then the less restrictive should be prefered. The simple answer is just that null is the default way to represent missing data in Java, whether you like it or not. In fact a lot of people don't like it and make it an argument for functional programming-style things. JIXiang You're oversimplifying what null is. Other valid interpretations could be "Unknown," "Not Applicable," or "Uninitialized.
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