What Is @Suppresswarnings Notation Inwards Java? Unchecked, Rawtypes, Serial

@SuppressWarnings notation is 1 of the 3 built-in annotations available inwards JDK together with added amongst @Override and @Deprecated inwards Java 1.5. @SuppressWarnings learn the compiler to ignore or suppress, specified compiler alert inwards annotated chemical constituent together with all programme elements within that element. For example, if a shape is annotated to suppress a particular warning, hence a alert generated inwards a method within that shape volition likewise last separated. You mightiness receive got seen @SuppressWarnings("unchecked") together with @SuppressWarnings("serial"), ii of most pop examples of @SuppressWarnings annotation. Former is used to suppress alert generated due to unchecked casting spell the subsequently alert is used to remind close adding SerialVersionUID inwards a Serializable class.

Since @SuppressWarnings indicates potential programming error or mistake, it's recommended to piece of work them sparingly together with instead endeavor to laid upwardly actual occupation which is triggering that warning. Having said that, in that place are conditions, specially spell using generics inwards Java, when y'all are absolutely certain that things won't cash inwards one's chips wrong, y'all tin piece of work @SuppressWarnings to suppress those warnings.

Also, worth next are advised  given past times Josh Bloch inwards his famous mass Effective Java, a must read for every Java programmer, to document argue for suppressing a alert equally a comment.

List of @SuppressWarnings options on Java

Different compiler together with IDEs back upwardly unlike listing of @SuppressWarnings options. It seems IDE similar Eclipse together with Netbeans back upwardly to a greater extent than options than standard javac compiler.

You tin acquire a listing of supported @SuppressWarnings choice for Java compiler, past times running javac -X command. Here is supported choice for javac 1.6.0_26.

$ javac -version   javac 1.6.0_26  $ javac -X   -Xlint  Enable recommended warnings   -Xlint:{all,cast,deprecation,divzero,empty,unchecked,fallthrough,path,serial,finally,overrides,-cast,-deprecation,-divzero,-empty,-unchecked,-fallthrough,-path,-serial,-finally,-overrides,none}Enable or disable specific warnings

You tin run into supported values of @SuppressWarnings are :

• all
• cast
• deprecation
• divzero
• empty
• unchecked
• fallthrough
• path
• serial
• finally
• overrides

You volition run into examples of a pair of these options, inwards our illustration of how to piece of work @SuppressWarnings notation inwards Java. To larn to a greater extent than close why y'all should suppress warnings, run into Effective Java 2d Edition past times Joshua Bloch.

How to @SuppressWarnings inwards Java?

In the in conclusion pair of  paragraphs, nosotros receive got seen what is @SuppressWarnings together with listing of @SuppressWarnings options supported past times javac compiler. Now nosotros volition see, when these warnings occur together with how does it assist to minimize potential errors?

If y'all are coding inwards Eclipse IDE, hence y'all are probable to run into many warnings equally before long equally y'all write code, which triggers whatsoever of these warnings. If y'all are compiling using javac, hence y'all won't run into all of these warnings, until y'all compile using -Xlint option.

javac -Xlint volition demo all warnings supported past times javac compiler. One of the simplest examples is implementing Serializable interface together with forget to declare SerialVersionUID, which could interruption your application inwards hereafter if the construction of shape changes.

Eclipse volition demo a alert with underlined zigzag inwards yellowish color. Now if y'all desire to suppress that alert y'all tin piece of work @SuppressWarnings("serial") at your shape score equally shown below :

import java.io.Serializable;  @SuppressWarnings("serial") public class Test implements Serializable{     private String version;     public String getVersion(){ return version }; }

Similarly, if y'all receive got used raw types i.e. Collections without generic, Eclipse volition demo y'all "rawtypes" alert equally shown below :

public class RawType{     public static void main(String args[]){         @SuppressWarnings("rawtypes")         List names = new ArrayList();     } }

here, nosotros receive got used ArrayList equally raw-type, together with Eclipse is quick to dot out that. Now, if y'all type Ctrl+1 which is Eclipse shortcut for demo hint, it volition plough over y'all the choice to piece of work @SuppressWarnings at master copy (method level) or at names (local variable level), ever direct the lowest level, which is a local variable inwards this case. If y'all direct to position @SuppressWarnings("rawtypes") at the method level, Eclipse volition suppress all raw-types warnings within that method.

If nosotros compile same code without @SuprressWarnings, using javac compiler it volition demo the next hint:

$ javac RawType.java Note: RawType.java uses unchecked or dangerous operations. Note: Recompile with -Xlint:unchecked for details.

together with when y'all compile this code with java -Xlint, it volition demo detailed warnings:

$ javac -Xlint RawType.java RawType.java:5: warning: [unchecked] unchecked conversion works life   : java.util.ArrayList required: java.util.List                 List names = new ArrayList();

Similarly for an unused variable, Eclipse shows warnings, which tin last suppressed past times @SuppressWarnings(unused). Remember, past times issuing these warnings, IDE together with compiler assist to discovery potential bugs at code fourth dimension together with compile time.

Best Practices using @SuppressWarnings notation inwards Java

Here are pair of things, which y'all tin proceed inwards take heed spell using @SuppressWarnings("") annotations:

1) Never position @SuppressWarnings("unchecked) or other options, at the shape level, this would potentially mask critical warnings.


2) Use @SuppressWarnings at the smallest scope. Which agency if the alert tin last removed past times putting @SuppressWarnings at a local variable hence piece of work that instead of annotating whole method. It's likewise worth knowing that suppress warnings notation tin last applied to class, field, method, parameter, constructor together with local variables.


3) While using @SuppressWarnings("unchecked"), add together a comment to explicate close "why a particular percentage of code is type-safe" earlier suppressing this warning. Every unchecked alert is an indication of potential ClassCastException at runtime, hence don't ignore them.


4) Don't piece of work @SuppressWarnings("all"), it volition suppress all warnings, which tin mask potential warnings which could Pb to RuntimeException when y'all run the program.


That's all on what is @SuppressWarnings inwards Java, listing of options supported past times @SuppressWarnings together with how to piece of work them at class, method together with plain level. It's of import to piece of work them correctly, together with y'all tin direct to pay attending to around of them. At the same time, I don't propose to suppress every alert shown past times Eclipse, because it volition clutter your code with lots of annotation, instead direct one's which actually matters e.g. serial, uncheck or rawtypes.

Further Learning
Complete Java Masterclass
Java Fundamentals: The Java Language
Java In-Depth: Become a Complete Java Engineer!

Share this post