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

@SuppressWarnings notation is i of the 3 built-in annotations available inward JDK as well as added amongst @Override and @Deprecated inward Java 1.5. @SuppressWarnings learn the compiler to ignore or suppress, specified compiler alarm inward annotated chemical constituent as well as all plan elements within that element. For example, if a flat is annotated to suppress a particular warning, as well as thence a alarm generated inward a method within that flat volition every bit good live separated. You mightiness receive got seen @SuppressWarnings("unchecked") as well as @SuppressWarnings("serial"), ii of most pop examples of @SuppressWarnings annotation. Former is used to suppress alarm generated due to unchecked casting piece the later on alarm is used to remind most adding SerialVersionUID inward a Serializable class.

Since @SuppressWarnings indicates potential programming error or mistake, it's recommended to role them sparingly as well as instead effort to produce actual work which is triggering that warning. Having said that, at that topographic point are conditions, particularly piece using generics inward Java, when you lot are absolutely certain that things won't boot the bucket wrong, you lot tin role @SuppressWarnings to suppress those warnings.

Also, worth next are advised  given past times Josh Bloch inward his famous majority Effective Java, a must read for every Java programmer, to document argue for suppressing a alarm every bit a comment.

List of @SuppressWarnings options on Java

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

You tin acquire a listing of supported @SuppressWarnings pick for Java compiler, past times running javac -X command. Here is supported pick 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 distich of these options, inward our illustration of how to role @SuppressWarnings notation inward Java. To larn to a greater extent than most why you lot should suppress warnings, run into Effective Java 2d Edition past times Joshua Bloch.

How to @SuppressWarnings inward Java?

In the lastly distich of  paragraphs, nosotros receive got seen what is @SuppressWarnings as well as listing of @SuppressWarnings options supported past times javac compiler. Now nosotros volition see, when these warnings move on as well as how does it aid to minimize potential errors?

If you lot are coding inward Eclipse IDE, as well as thence you lot are probable to run into many warnings every bit shortly every bit you lot write code, which triggers whatsoever of these warnings. If you lot are compiling using javac, as well as thence you lot won't run into all of these warnings, until you lot compile using -Xlint option.

javac -Xlint volition demonstrate all warnings supported past times javac compiler. One of the simplest examples is implementing Serializable interface as well as forget to declare SerialVersionUID, which could pause your application inward futurity if the construction of flat changes.

Eclipse volition demonstrate a alarm with underlined zigzag inward yellowish color. Now if you lot desire to suppress that alarm you lot tin role @SuppressWarnings("serial") at your flat story every bit shown below :

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

Similarly, if you lot receive got used raw types i.e. Collections without generic, Eclipse volition demonstrate you lot "rawtypes" alarm every bit shown below :

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

here, nosotros receive got used ArrayList every bit raw-type, as well as Eclipse is quick to dot out that. Now, if you lot type Ctrl+1 which is Eclipse shortcut for demonstrate hint, it volition laissez passer on you lot the pick to role @SuppressWarnings at principal (method level) or at names (local variable level), ever direct the lowest level, which is a local variable inward this case. If you lot direct to set @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 demonstrate the next hint:

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

as well as when you lot compile this code with java -Xlint, it volition demonstrate detailed warnings:

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

Similarly for an unused variable, Eclipse shows warnings, which tin live suppressed past times @SuppressWarnings(unused). Remember, past times issuing these warnings, IDE as well as compiler aid to honour potential bugs at code fourth dimension as well as compile time.

Best Practices using @SuppressWarnings notation inward Java

Here are distich of things, which you lot tin proceed inward hear piece using @SuppressWarnings("") annotations:

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


2) Use @SuppressWarnings at the smallest scope. Which agency if the alarm tin live removed past times putting @SuppressWarnings at a local variable as well as thence role that instead of annotating whole method. It's every bit good worth knowing that suppress warnings notation tin live applied to class, field, method, parameter, constructor as well as local variables.


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


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


That's all on what is @SuppressWarnings inward Java, listing of options supported past times @SuppressWarnings as well as how to role them at class, method as well as champaign level. It's of import to role them correctly, as well as you lot tin direct to pay attending to about of them. At the same time, I don't propose to suppress every alarm 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!

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