To handle the null values in your data which method is used?

by Christian Neumanns A quick and thorough guide to ‘ null’: what it is, and how you should use it What is the meaning of null? How is null implemented? When should you use null in your source code, and when should you not use it? Introduction null is a fundamental concept in many programming languages. It is ubiquitous in all kinds of source code written in these languages. So it is essential to fully grasp the idea of null . We have to understand its semantics and implementation, and we need to know how to use null in our source code. Comments in programmer forums sometimes reveal a bit of confusion with null. Some programmers even try to completely avoid null. Because they think of it as the 'million-dollar mistake', a term coined by Tony Hoare, the inventor of null. Here is a simple example: Suppose that Alice’s email_address points to null. What does this mean? Does it mean that Alice doesn't have an email address? Or that her email address is unknown? Or that it is secret? Or does it simply mean that email_address is 'undefined' or 'uninitialized'? Let's see. After reading this article, everybody should be able to answer such questions without hesitation. Note: This article is programming-language-neutral — as far as possible. Explanations are general and not tied to a specific language. Please consult your programming language manuals for specific advice on null. However, this article contains some simple source code examples shown in Java. But it’s not difficult to...

I want to have a spring data repository interface that takes two parameters. Is there a way to make it have the following behaviour? MyObject findByParameterOneAndParameterTwo( String parameterOne, String parameterTwo); If both parameters have a value, I would like it to behave normally and do an "AND" for both values. If for example the second parameter is null, then it would search only by ParameterOne Any suggestions? The mechanism of deriving a query out of a repository method name provided by Spring Data is meant for cases where the query is known in advance. It is not practical to expect that mechanism to work with queries that are precisely known only at runtime. For dynamic situations there are several other options such as @Query and QueryDSL. SQL and JPA support the COALESCE function, which can be used to work around a parameter that can sometimes have a NULL value. @Query("SELECT e FROM MyObject e WHERE COALESCE(e.parameterOne, ?1) = ?1 AND COALESCE(e.parameterOne, ?2) = ?2") should work. @Forward, I have only given a direction to the poster as I am not sure about how the poster wants the matching to work exactly. For example, it has not been specified whether the database can contain null values for those columns and if yes, how should matching work, and so on. But yes, based just on what has been posted, your comment is spot on. One solution that's missing here is Spring Data JPA's ExampleMatcher#ignoreNullValues, which is built exactly to solve this problem. ...

Before calling a function of an object, I need to check if the object is null, to avoid throwing a NullPointerException. What is the best way to go about this? I've considered these methods. Which one is the best programming practice for Java? // Method 1 if (foo != null) • Do not catch NullPointerException. That is a bad practice. It is better to ensure that the value is not null. • Method #4 will work for you. It will not evaluate the second condition, because Java has short-circuiting (i.e., subsequent conditions will not be evaluated if they do not change the end-result of the boolean expression). In this case, if the first expression of a logical AND evaluates to false, subsequent expressions do not need to be evaluated. Method 4 is far and away the best as it clearly indicates what will happen and uses the minimum of code. Method 3 is just wrong on every level. You know the item may be null so it's not an exceptional situation it's something you should check for. Method 2 is just making it more complicated than it needs to be. Method 1 is just method 4 with an extra line of code. Method 3 is what you'd normally do in Python. Rather than "You know the item may be null so it's not an exceptional situation" you could say "You know that in exceptional situations (like a file is missing somewhere) it will be null". I don't know why java developers are so afraid of exceptions. What's the point of adding exceptions capability to the language if you still have to check retu...