Re: can't throw

From:

=?ISO-8859-1?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 12 Sep 2012 21:54:39 -0400

Message-ID:

<50513ce1$0$288$14726298@news.sunsite.dk>

On 9/12/2012 9:37 PM, Arne Vajh?j wrote:

On 9/12/2012 9:29 PM, Gene Wirchenko wrote:

I had to catch the exceptions or get a compilation error for each
one I missed.

No.

You has to catch them *or* pass them back the caller by adding throws to
the method signature.

If the method can not really do anything about the exception then
the last option is what should be used.

Not:

public class Wrong {
    public static class ExceptionA extends Exception {
    }
    public static class ExceptionA1 extends ExceptionA {
    }
    public static class ExceptionA2 extends ExceptionA {
    }
    public static class ExceptionA3 extends ExceptionA {
    }
    public static class ExceptionB extends Exception {
    }
    public static class ExceptionB1 extends ExceptionB {
    }
    public static class ExceptionB2 extends ExceptionB {
    }
    public static class ExceptionB3 extends ExceptionB {
    }
    public static class ExceptionC extends Exception {
    }
    public static class ExceptionC1 extends ExceptionC {
    }
    public static class ExceptionC2 extends ExceptionC {
    }
    public static class ExceptionC3 extends ExceptionC {
    }
    public static class SomeLib {
        public void a() throws ExceptionA1, ExceptionA2 {
        }
        public void aa() throws ExceptionA2, ExceptionA3 {
        }
        public void b() throws ExceptionB1, ExceptionB2 {
        }
        public void bb() throws ExceptionB2, ExceptionB3 {
        }
        public void c() throws ExceptionC1, ExceptionC2 {
        }
        public void cc() throws ExceptionC2, ExceptionC3 {
        }
    }
    public static void m2() {
        SomeLib lib = new SomeLib();
        try {
            lib.a();
            lib.aa();
            lib.b();
            lib.bb();
            lib.c();
            lib.cc();
        } catch (ExceptionA1 e) {
            e.printStackTrace();
            System.exit(1);
        } catch (ExceptionA2 e) {
            e.printStackTrace();
            System.exit(1);
        } catch (ExceptionA3 e) {
            e.printStackTrace();
            System.exit(1);
        } catch (ExceptionB1 e) {
            e.printStackTrace();
            System.exit(1);
        } catch (ExceptionB2 e) {
            e.printStackTrace();
            System.exit(1);
        } catch (ExceptionB3 e) {
            e.printStackTrace();
            System.exit(1);
        } catch (ExceptionC1 e) {
            e.printStackTrace();
            System.exit(1);
        } catch (ExceptionC2 e) {
            e.printStackTrace();
            System.exit(1);
        } catch (ExceptionC3 e) {
            e.printStackTrace();
            System.exit(1);
        }
    }
    public static void m1() {
        m2();
    }
    public static void main(String[] args) {
        m1();
    }
}

but:

public class Correct {
    public static class ExceptionA extends Exception {
    }
    public static class ExceptionA1 extends ExceptionA {
    }
    public static class ExceptionA2 extends ExceptionA {
    }
    public static class ExceptionA3 extends ExceptionA {
    }
    public static class ExceptionB extends Exception {
    }
    public static class ExceptionB1 extends ExceptionB {
    }
    public static class ExceptionB2 extends ExceptionB {
    }
    public static class ExceptionB3 extends ExceptionB {
    }
    public static class ExceptionC extends Exception {
    }
    public static class ExceptionC1 extends ExceptionC {
    }
    public static class ExceptionC2 extends ExceptionC {
    }
    public static class ExceptionC3 extends ExceptionC {
    }
    public static class SomeLib {
        public void a() throws ExceptionA1, ExceptionA2 {
        }
        public void aa() throws ExceptionA2, ExceptionA3 {
        }
        public void b() throws ExceptionB1, ExceptionB2 {
        }
        public void bb() throws ExceptionB2, ExceptionB3 {
        }
        public void c() throws ExceptionC1, ExceptionC2 {
        }
        public void cc() throws ExceptionC2, ExceptionC3 {
        }
    }
    public static void m2() throws ExceptionA, ExceptionB, ExceptionC {
        SomeLib lib = new SomeLib();
        lib.a();
        lib.aa();
        lib.b();
        lib.bb();
        lib.c();
        lib.cc();
    }
    public static void m1() throws ExceptionA, ExceptionB, ExceptionC {
        m2();
    }
    public static void main(String[] args) {
        try {
            m1();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(1);
        }
    }
}

Arne