@suppresswarnings serial unchecked

ArrayList; import java. As in the code, it is using the SuppressWarnings annotation to do not to fix that warning. Next, we write the java code to understand the SuppressWarnings annotation more clearly with the following example where we use SuppressWarnings to suppress deprecationwarning, as below —.

Next, we write the java code to understand the SuppressWarnings annotation where we use SuppressWarnings to suppress deprecation warning at the class level, as below —.

If we use the SuppressWarnings annotation at the main method level in the above code, the warning message will show in the anotherMethod method, as we can clearly see in the below image.

Next, we write the java code to understand the SuppressWarnings annotation where we use SuppressWarnings to suppress multiple warnings at as below —. List; import javax. The SuppressWarningsis an annotation in Java which informs the compiler to ignore the specified warnings for a certain part of the program where it is annotated. This is a guide to SuppressWarnings in Java.

Here we an introduction to SuppressWarnings in java with appropriate syntax, parameters and working with examples. You can also go through our other related articles to learn more —. Submit Next Question. By signing up, you agree to our Terms of Use and Privacy Policy. Forgot Password? This website or its third-party tools use cookies, which are necessary to its functioning and required to achieve the purposes illustrated in the cookie policy.

It is an annotation to suppress compile warnings about unchecked generic operations not exceptions , such as casts. It essentially implies that the programmer did not wish to be notified about these which he is already aware of when compiling a particular bit of code.

It could also mean that the current Java type system version isn't good enough for your case. If you really need this supression, narrow it down as much as possible e. An example:. If I didn'n anotate the SuppressWarnings "unchecked" here, it would have a problem with line, where I want to return my ResultList. In shortcut type-safety means: A program is considered type-safe if it compiles without errors and warnings and does not raise any unexpected ClassCastException s at runtime.

The SuppressWarning annotation is used to suppress compiler warnings for the annotated element. Specifically, the unchecked category allows suppression of compiler warnings generated as a result of unchecked type casts. Java Virtual Machine has no idea what generic types are while running a program, so this compiles and runs, as for Java Virtual Machine, this is a cast to List type this is the only thing it can verify, so it verifies only that.

An unchecked warning tells a programmer that a cast may cause a program to throw an exception somewhere else. Suppressing the warning with SuppressWarnings "unchecked" tells the compiler that the programmer believes the code to be safe and won't cause unexpected exceptions.

Why would you want to do that? Java type system isn't good enough to represent all possible type usage patterns. Sometimes you may know that a cast is safe, but Java doesn't provide a way to say so - to hide warnings like this, SupressWarnings "unchecked" can be used, so that a programmer can focus on real warnings. For instance, Optional. This cast is safe, as the value stored in an empty optional cannot be retrieved so there is no risk of unexpected class cast exceptions. You can suppress the compiler warnings and tell the generics that the code which you had written is legal according to it.

As far I know, for now it has to do with suppressing warnings about generics; generics are a new programming construct not supported in JDK versions earlier than JDK 5, so any mixes of the old constructs with the new ones might pose some unexpected results. The compiler warns the programmer about it, but if the programmer already knows, they can turn those dreaded warnings off using SuppressWarnings. A warning by which the compiler indicates that it cannot ensure type safety.

The term "unchecked" warning is misleading. It does not mean that the warning is unchecked in any way. The term "unchecked" refers to the fact that the compiler and the runtime system do not have enough type information to perform all type checks that would be necessary to ensure type safety. In this sense, certain operations are "unchecked". The most common source of "unchecked" warnings is the use of raw types. When the add method is invoked the compiler does not know whether it is safe to add a String object to the collection.

If the TreeSet is a collection that contains String s or a supertype thereof , then it would be safe. But from the type information provided by the raw type TreeSet the compiler cannot tell. Hence the call is potentially unsafe and an "unchecked" warning is issued. Example of an unchecked warning in conjunction with a cast to a parameterized type or type variable :.

A cast whose target type is either a concrete or bounded wildcard parameterized type or a type parameter is unsafe, if a dynamic type check at runtime is involved.

At runtime, only the type erasure is available, not the exact static type that is visible in the source code. As a result, the runtime part of the cast is performed based on the type erasure, not on the exact static type.

In the example, the cast to Wrapper would check whether the object returned from super. Similarly, the casts to the type parameter T are cast to type Object at runtime, and probably optimized away altogether. Due to type erasure, the runtime system is unable to perform more useful type checks at runtime. In a way, the source code is misleading, because it suggests that a cast to the respective target type is performed, while in fact the dynamic part of the cast only checks against the type erasure of the target type.

The "unchecked" warning is issued to draw the programmer's attention to this mismatch between the static and dynamic aspect of the cast. Please refer: What is an "unchecked" warning? SuppressWarnings annotation is one of the three built-in annotations available in JDK and added alongside Override and Deprecated in Java 1.

SuppressWarnings instruct the compiler to ignore or suppress, specified compiler warning in annotated element and all program elements inside that element. For example, if a class is annotated to suppress a particular warning, then a warning generated in a method inside that class will also be separated. You might have seen SuppressWarnings "unchecked" and SuppressWarnings "serial" , two of most popular examples of SuppressWarnings annotation. Former is used to suppress warning generated due to unchecked casting while the later warning is used to remind about adding SerialVersionUID in a Serializable class.

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Learn more. What is SuppressWarnings "unchecked" in Java? Ask Question. Asked 12 years, 6 months ago.