Throwing multiple exceptions in a method of an interface in java

Question

I wanted to ask that how to mention this in my interface   public class find int x  throws A Exception  B Exception  ---- ---- ---     i want to say that i can mention One exception in an interface but how to mention in my interface that my method will throw Two exceptions Namely A and B     the code fragment mentioned above works only for A and not for B    Help  public interface dictionary      public void insert int x  throws Dictionary FullException  Duplicate Element FoundException          public class SortedArray implements dictionary      public void insert int x  throws Dictionary FullException  Duplicate Element FoundException    ---------     but when i compile it     it says       SortedArray java 66  insert int  in   assign SortedArray cannot implement   insert int  in assign dictionary    overridden method does not throw   assign SortedArray Duplicate Element FoundException public   void insert int x  throws   Dictionary FullException

User · Answer

I think you are asking for something like the code below:

public interface A
{
    void foo() 
        throws AException;
}

public class B
    implements A
{
    @Overrides 
    public void foo()
        throws AException,
               BException
    {
    }
}

This will not work unless BException is a subclass of AException. When you override a method you must conform to the signature that the parent provides, and exceptions are part of the signature.

The solution is to declare the the interface also throws a BException.

The reason for this is you do not want code like:

public class Main
{
    public static void main(final String[] argv)
    {
        A a;

        a = new B();

        try
        {
            a.foo();
        }
        catch(final AException ex)
        {
        }
        // compiler will not let you write a catch BException if the A interface
        // doesn't say that it is thrown.
    }
}

What would happen if B::foo threw a BException? The program would have to exit as there could be no catch for it. To avoid situations like this child classes cannot alter the types of exceptions thrown (except that they can remove exceptions from the list).

User · Answer

You need to specify it on the methods that can throw the exceptions  You just seperate them with a     if it can throw more than 1 type of exception  e g   public interface MyInterface     public MyObject find int x  throws MyExceptionA MyExceptionB

User · Answer

You can declare as many Exceptions as you want for your interface method  But the class you gave in your question is invalid  It should read  public class MyClass implements MyInterface     public void find int x  throws A Exception  B Exception      ----     ----     ---         Then an interface would look like this  public interface MyInterface     void find int x  throws A Exception  B Exception

[java] Throwing multiple exceptions in a method of an interface in java

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