BE the compiler, advanced

collections
with
generics
you are here
4
577
import
java.util.*
;
public class SortMountains {
LinkedList

mtn = new LinkedList

();
class NameCompare
implements Comparator
{
public int compare(Mountain one, Mountain two) {
return
one.name.compareTo(two.name)
;
}
}
class HeightCompare
implements Comparator
{
public int compare(Mountain one, Mountain two) {
return (
two.height - one.height
);
}
}
public static void main(String [] args) {
new SortMountain().go();
}
public void go() {
mtn.add(new Mountain(“Longs”, 14255));
mtn.add(new Mountain(“Elbert”, 14433));
mtn.add(new Mountain(“Maroon”, 14156));
mtn.add(new Mountain(“Castle”, 14265));
System.out.println(“as entered:\n” + mtn);
NameCompare nc = new NameCompare();
Collections.sort(mtn, nc)
;
System.out.println(“by name:\n” + mtn);
HeightCompare hc = new HeightCompare();
Collections.sort(mtn, hc)
;
System.out.println(“by height:\n” + mtn);
}
}
class Mountain {
String name
;
int height
;
Mountain(String n, int h)
{
name = n
;
height = h
;
}
public String toString( )
{
return name + “ “ + height
;
}
File Edit Window Help ThisOne’sForBob
%java SortMountains
as entered:
[Longs 14255, Elbert 14433, Maroon 14156, Castle 14265]
by name:
[Castle 14265, Elbert 14433, Longs 14255, Maroon 14156]
by height:
[Elbert 14433, Castle 14265, Longs 14255, Maroon 14156]
Output:
Did you notice that the height list is
in DESCENDING sequence ? : )
Solution to the “Reverse
Engineer” sharpen exercise

578

chapter 16
Given the following compilable statement:

Collections.sort(myArrayList);
1. What must the class of the objects stored in
myArrayList
implement?
Comparable
2. What method must the class of the objects stored in
myArrayList
implement?
compareTo( )
3. Can the class of the objects stored in
myArrayList
implement both
Comparator
AND
Comparable
?
yes
Given the following compilable statement:

Collections.sort(myArrayList, myCompare);
4. Can the class of the objects stored in
myArrayList
implement
Comparable
?
yes
5. Can the class of the objects stored in
myArrayList
implement
Comparator
?

— Scott McNealy, Sun Microsystems Chairman, President and ceo

BE the compiler, advanced