collections example in scjp5 book!!!!

[manny singh]

In the example on page 557 , why we used a static class to implement
Comparator??

[Sandeep Bhandari]

can you show the full code??

[Dan Chisholm]

In the example on page 557 , why we used a static class to implement Comparator??

The code sample creates an instance of the static member type ReSortComparator within the static context of the main method. A static member type such as ReSortComparator can be created within the context of the main method even though no instance of SearchObjArray exists. If you were to delete the static modifier from the declaration of ReSortComparator, then ResortComparator could not be created within the static context of the main method because an enclosing instance of SearchObjArray would not be available.

import java.util.*;
class SearchObjArray {
public static void main (String [] args) {
ReSortComparator rsc = new ReSortComparator(); // This fails to compile.
}
void a() {
ReSortComparator rsc = new ReSortComparator();  // This is OK.
}
class ReSortComparator implements Comparator<String> {
public int compare (String a, String b) {
  return b.compareTo(a);
}
}
}

If you add the static modifier to the declaration of ReSortComparator, then it will compile.

[manny singh]

Thanks Sir

[manny singh]

import java.util.*;
class SearchObjArray {
public static void main (String [] args) {
SearchObjArray.ReSortComparator rsc = new SearchObjArray().new ReSortComparator();
}
class ReSortComparator implements Comparator<String> {
public int compare (String a, String b) {
return b.compareTo(a);
}
}
}

???THIS IS COMPILING???

[Dan Chisholm]

???THIS IS COMPILING???

Yes, you provided an enclosing instance of SearchObjArray for your non-static inner class, ReSortComparator.

[Bert Bates]

Hey Dan,

How are you doing dude?!

[manny singh]

thanks

[Dan Chisholm]

Originally posted by Bert Bates:
Hey Dan,

How are you doing dude?!

I'm doing fine.

It looks like you've published a few more books since I was last here at the JavaRanch. I like your Java 5 study guide, and I often recommend it to anyone that's interested in Java and the certification exam. I'm sure that the Java 6 version will also be great when it becomes available this summer.