My small contribution: What is transient variable in Java? In simple sentence any variable which is modified with transient keyword becomes transient variable in java. Why do we need transient variable in java?

How To Install Windows Over The Network. Transient keyword provides you some control over serialization process and gives you flexibility to exclude some of object properties from serialization process. Some time it does make sense not to serialize certain attributes of an object, we will see which variables should not be serialized and should be made transient in next section. Which variable you should mark transient? Since we know the purpose of transient keyword or having transient variable its make sense to think about which variable should be marked as transient. My rule is that any variable whose value can be calculated from other variables doesn't require to be saved.

For example if you have a field called 'interest' whose value can be derived from other fields e.g. Principle, rate, time etc then there is no need to serialize it. Another example is of word count, if you are saving article then no need to save word count, because it can be created when article gets deserialized. Another good example of transient keyword is 'Logger' since most of the time you have logger instance for logging in Java but you certainly don't want it to serialize correct? @TFennis: If a serializable class A references a not serializable class B (like Thread in your example), then A must either mark the reference as transient XOR must override the default serialization process in order to do something reasonable with B XOR assume that only serializable subclasses of B are actually referenced (so the actual subclass must take care for their 'bad' parent B) XOR accept that the serialization will fail. In only one case (marked as transient) B is automatically and silently skipped. – Nov 26 '13 at 22:45 3.

Serialization systems other than the native java one can also use this modifier. Hibernate, for instance, will not persist fields marked with either @Transient or the transient modifier. Terracotta as well respects this modifier. I believe the figurative meaning of the modifier is 'this field is for in-memory use only. Don't persist or move it outside of this particular VM in any way.

JSX serializes Java objects to XML. You can persist objects, evolve them, and send them over the network and between applications. A COMPARISON OF MICROSOFT'S C# PROGRAMMING LANGUAGE TO SUN MICROSYSTEMS' JAVA PROGRAMMING LANGUAGE By Dare Obasanjo Introduction. The C# language is an object.

Its non-portable'. You can't rely on its value in another VM memory space. Much like volatile means you can't rely on certain memory and thread semantics. As per google transient meaning == lasting only for a short time; impermanent.

Now if want to make anything transient in java use transient keyword. Q: where to use transient? A: Generally in java we can save data to files by acquiring them in variables and writing those variables to files, this process is known as Serialization. Now if we want to avoid variable data to be written to file, we would make that variable as transient. Transient int result=10; Note: transient variables cannot be local.

The docs for are probably about as good an explanation as you'll get: The serialization runtime associates with each serializable class a version number, called a serialVersionUID, which is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible with respect to serialization. If the receiver has loaded a class for the object that has a different serialVersionUID than that of the corresponding sender's class, then deserialization will result in an InvalidClassException. A serializable class can declare its own serialVersionUID explicitly by declaring a field named ' serialVersionUID' that must be static, final, and of type long: ANY-ACCESS-MODIFIER static final long serialVersionUID = 42L; If a serializable class does not explicitly declare a serialVersionUID, then the serialization runtime will calculate a default serialVersionUID value for that class based on various aspects of the class, as described in the Java(TM) Object Serialization Specification. However, it is strongly recommended that all serializable classes explicitly declare serialVersionUID values, since the default serialVersionUID computation is highly sensitive to class details that may vary depending on compiler implementations, and can thus result in unexpected InvalidClassExceptions during deserialization. Therefore, to guarantee a consistent serialVersionUID value across different java compiler implementations, a serializable class must declare an explicit serialVersionUID value. It is also strongly advised that explicit serialVersionUID declarations use the private modifier where possible, since such declarations apply only to the immediately declaring class--serialVersionUID fields are not useful as inherited members.

If you're serializing just because you have to serialize for the implementation's sake (who cares if you serialize for an HTTPSession, for instance.if it's stored or not, you probably don't care about de-serializing a form object), then you can ignore this. If you're actually using serialization, it only matters if you plan on storing and retrieving objects using serialization directly. The serialVersionUID represents your class version, and you should increment it if the current version of your class is not backwards compatible with its previous version.

Most of the time, you will probably not use serialization directly. If this is the case, generate a default serializable uid by clicking the quick fix option and don't worry about it. 'You should increment it if the current version of your class is not backwards compatible with its previous version:' You should first explore the extensive object versioning support of Serialization, (a) to ensure that the class really is now serialization-incompatible way, which per the specification is quite difficult to achieve; (b) to try a scheme such as custom read/writeObject() methods, readResolve/writeReplace() methods, serializableFields declarations, etc, to make sure that the stream remains compatible. Changing the actual serialVersionUID is a last resort, a counsel of despair. – Dec 12 '12 at 0:59 2. I can't pass up this opportunity to plug Josh Bloch's book (2nd Edition). Chapter 11 is an indispensible resource on Java serialization.

Per Josh, the automatically-generated UID is generated based on a class name, implemented interfaces, and all public and protected members. Changing any of these in any way will change the serialVersionUID. So you don't need to mess with them only if you are certain that no more than one version of the class will ever be serialized (either across processes or retrieved from storage at a later time).

If you ignore them for now, and find later that you need to change the class in some way but maintain compatibility w/ old version of the class, you can use the JDK tool serialver to generate the serialVersionUID on the old class, and explicitly set that on the new class. (Depending on your changes you may need to also implement custom serialization by adding writeObject and readObject methods - see Serializable javadoc or aforementioned chapter 11.).

It is worth noting that Joshua Bloch advices that for every Serializable class it's worth specifying the serial version uid. Quote from chapter 11: Regardless of what serialized form you choose, declare an explicit serial version UID in every serializable class you write. This eliminates the serial version UID as a potential source of incompatibility (Item 74). There is also a small performance benefit. If no serial version UID is provided, an expensive computation is required to generate one at runtime.

– Jul 8 '14 at 13:25. You can tell Eclipse to ignore these serialVersionUID warnings: Window >Preferences >Java >Compiler >Errors / Warnings >Potential Programming Problems In case you didn't know, there are a lot of other warnings you can enable in this section (or even have some reported as errors), many are very useful: • Potential Programming Problems: Possible accidental boolean assignment • Potential Programming Problems: Null pointer access • Unnecessary code: Local variable is never read • Unnecessary code: Redundant null check • Unnecessary code: Unnecessary cast or 'instanceof' and many more. SerialVersionUID facilitates versioning of serialized data. Its value is stored with the data when serializing. When de-serializing, the same version is checked to see how the serialized data matches the current code.

If you want to version your data, you normally start with a serialVersionUID of 0, and bump it with every structural change to your class which alters the serialized data (adding or removing non-transient fields). The built-in de-serialization mechanism ( in.defaultReadObject()) will refuse to de-serialize from old versions of the data. But if you want to you can define your own -function which can read back old data.

Dimonized Unp Female Body Download Adobe. This custom code can then check the serialVersionUID in order to know which version the data is in and decide how to de-serialize it. This versioning technique is useful if you store serialized data which survives several versions of your code. But storing serialized data for such a long time span is not very common. It is far more common to use the serialization mechanism to temporarily write data to for instance a cache or send it over the network to another program with the same version of the relevant parts of the codebase. In this case you are not interested in maintaining backwards compatibility.

You are only concerned with making sure that the code bases which are communicating indeed have the same versions of relevant classes. In order to facilitate such a check, you must maintain the serialVersionUID just like before and not forget to update it when making changes to your classes. If you do forget to update the field, you might end up with two different versions of a class with different structure but with the same serialVersionUID. If this happens, the default mechanism ( in.defaultReadObject()) will not detect any difference, and try to de-serialize incompatible data. Now you might end up with a cryptic runtime error or silent failure (null fields). These types of errors might be hard to find.

So to help this usecase, the Java platform offers you a choice of not setting the serialVersionUID manually. Instead, a hash of the class structure will be generated at compile-time and used as id. This mechanism will make sure that you never have different class structures with the same id, and so you will not get these hard-to-trace runtime serialization failures mentioned above. But there is a backside to the auto-generated id strategy.

Namely that the generated ids for the same class might differ between compilers (as mentioned by Jon Skeet above). So if you communicate serialized data between code compiled with different compilers, it is recommended to maintain the ids manually anyway. And if you are backwards-compatible with your data like in the first use case mentioned, you also probably want to maintain the id yourself. This in order to get readable ids and have greater control over when and how they change. What is a serialVersionUID and why should I use it?

SerialVersionUID is a unique identifier for each class, JVM uses it to compare the versions of the class ensuring that the same class was used during Serialization is loaded during Deserialization. Specifying one gives more control, though JVM does generate one if you don't specify. The value generated can differ between different compilers. Furthermore, sometimes you just want for some reason to forbid deserialization of old serialized objects [ backward incompatibility], and in this case you just have to change the serialVersionUID. Java docs says: 'the default serialVersionUID computation is highly sensitive to class details that may vary depending on compiler implementations, and can thus result in unexpected InvalidClassExceptions during deserialization'. You must declare serialVersionUID because it give us more control.

Has some good points on the topic. The one thing not mentioned in this answer is that you may cause unintended consequences by blindly including serialVersionUID without knowing why.

Tom Anderson's comment on MetroidFan2002's answer addresses this: 'I'd say that if you're not using serialization for permanent storage, you should use @SuppressWarnings rather than adding a value. It clutters the class less, and it preserves the ability of the serialVersionUID mechanism to protect you from incompatible changes.' – Jun 17 '14 at 16:30 2. I think you're right that composition over inhneritance makes more sense, particularly when you're discussing classes such as ArrayList. However, many frameworks require people to extend from abstract superclasses which are serializable (such as Struts 1.2's ActionForm class, or Saxon's ExtensionFunctionDefinition) in which case this solution is infeasible. I think you're right, it would be nice if the warning were ignored in certain cases (like if you were extending from an abstract serializable class) – Dec 7 '11 at 15:20 2.