One of annoying error while overriding Java method in Eclipse IDE is must override a superclass method error , This error is quite frequent when importing Java projects and still I haven't seen any permanent solution of it. Must override a super class method error comes in Eclipse, if you have Java Class that implements interface and overrides method from interface and uses @Override annotation . Unfortunately Eclipse defaults to Java 1.5, which only recognize @Override annotation for overriding method from super class and not from interface. This creates lots of confusion between Java programmers as not every one is aware of this subtle difference of using @Override annotation with class and interface methods and they start looking classpath and path suspiciously. @Override annotation for interface methods are only available from Java 1.6 and if you use @Override while overriding interface method than you will get must override a superclass method error. In this Java and Eclipse tutorial we will see how to fix must override a superclass method error in eclipse but before that we will reproduce this error in a manner which will clear that Eclipse will complain only for methods which is overridden from interface.
Reproduce must override a superclass method error in Eclipse
In order to reproduce must override a superclass method error Just create an Eclipse project with compiler settings pointing to Java 1.5. Here is an example class for reproducing "must override a superclass method error" :
if you paste this Java program in Eclipse IDE with Java source settings 1.5 you will get error inside Test class run() method while HelloWorld class which overrides run() method from java.lang.Thread superclass will not throw any error.
How to fix must override a superclass method error
Fixing must override a superclass method error is not difficult, You just need to change Java source version to 1.6 because from Java 1.6 @Override annotation can be used along with interface method. In order to change source version to 1.6 follow below steps :
1) Select Project , Right click , Properties
2) Select Java Compiler and check the check box "Enable project specific settings"
3) Now make Compiler compliance level to 1.6
4) Apply changes
Here is screen short of changing compiler settings to use Java 1.6 to fix must override a superclass method error.
That's all on How to fix must override a superclass method error in Eclipse IDE. As soon as you do this change and if your build is set to automatic than Eclipse stops showing "must override a superclass method error" for any overridden method from interface. I know its pretty annoying and this subtle detail about @Override annotation is not obvious. let me know if you face ""must override a superclass method error" because of any other reason in Eclipse.
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