Re: Can a method be a parameter of another method in Java?

From:
Michael Rauscher <michlmann@gmx.de>
Newsgroups:
comp.lang.java.programmer
Date:
Wed, 13 Sep 2006 15:35:16 +0200
Message-ID:
<ee91a2$23vk$1@registered.motzarella.org>
Shawn schrieb:

Ingo R. Homann wrote:

Of course it can, see below. A great advantage of Java is, that its
solution is also typesafe!

Ciao,
Ingo

interface Mapper {
  int map(int d);
}

class Test {

 double sum(Mapper m, int a, int b) {
  int sum=0;
  for(int i=a;i<=b;i++) {
   sum+=m.map(i);
  }
  return sum;
 }

 void test() {
  System.out.println(sum(
   new Mapper(){public int map(int x) {return x*x;}},
   5,10));
  System.out.println(sum(
   new Mapper(){public int map(int x) {return (x+50)*(x+50);}},
   5,10));
  // ...
 }

}


Fantastic! Thank you very much. I didn't realize interface can be such a
use--place holder. I thought interface was only used in inheritance.

One more question about the "public" word:

interface Mapper {
   int map(int d); //Did you forget "public" here?
}


No, Ingo didn't forget the public. A interface only have public methods
so the public keyword may be omitted.

Bye
Michael

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