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

From:

Shawn <shaw@nospam.com>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 13 Sep 2006 09:10:14 -0400

Message-ID:

<ee8vvm$v0f$1@news.nems.noaa.gov>

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?
}
...
System.out.println(sum(
     new Mapper(){public int map(int x) {return x*x;}},
     5,10)); //I assume you add public here so Mapper m can access
..map(). If you omit it above, can you enforce it now?

Thank you again.