The Arrays class has another sort( ) method that takes a single argument: an array of Object, but with no Comparator...

Odnośniki

Smutek to uczucie, jak gdyby się tonęło, jak gdyby grzebano cię w ziemi.
object mcal_fetch_current_stream_event ( int stream) Zwraca bieżącą strukturę zdarzenia ze strumienia w postaci obiektu zawierający następujące...
class ColorPick{ static void Main(){Color favorite = SelectFavoriteColor();RespondToFavoriteColor(favorite);}static Color...
wybra� opcj� Information i nacisn�� ENTER, w rezultacie na ekranie pojawisi� zestaw informacji podobny do tego poni�ej:,j~%%I , Object ID: B6000006NetWare...
części doradców odrzucających z założenia jakiekolwiek argumenty wskazujące na specyfikę krajów posocjalistycznych (jako grupy) oraz wielkie różnice...
displaying output 3-9 dim argument for cat 19-7 distance between nodes 16-22 dimensions docking windows in desktop 2-10 deleting...
Every programming language enables some method for declaring local (or global) variables that can be used to store data...
Nigdy nie pragniemy z pasją czegoś, za czym przemawia tylko argument...
The Renaissance, penetrating northward, past first from Italy to France,but as early as the middle of the fifteenth century English students werefrequenting the...
zamęściem, bardziej niż jakikolwiek inny argument...
C# also supports the params modifier which allows a method to accept a variable number of parameters...

Smutek to uczucie, jak gdyby się tonęło, jak gdyby grzebano cię w ziemi.

This sort( ) method must also have some way to compare two Objects. It uses the natural comparison method that is imparted to a class by implementing the Comparable interface. This interface has a single method, Chapter 8: Holding Your Objects
321
compareTo( ), which compares the object to its argument and returns negative, zero, or positive depending on whether it is less than, equal to, or greater than the argument. A simple example demonstrates this:
//: CompClass.java
// A class that implements Comparable
package c08.newcollections;
import java.util.*;
public class CompClass implements Comparable {
private int i;
public CompClass(int ii) { i = ii; }
public int compareTo(Object o) {
// Implicitly tests for correct type:
int argi = ((CompClass)o).i;
if(i == argi) return 0;
if(i < argi) return -1;
return 1;
}
public static void print(Object[] a) {
for(int i = 0; i < a.length; i++)
System.out.print(a[i] + " ");
System.out.println();
}
public String toString() { return i + ""; }
public static void main(String[] args) {
CompClass[] a = new CompClass[20];
for(int i = 0; i < a.length; i++)
a[i] = new CompClass(
(int)(Math.random() *100));
print(a);
Arrays.sort(a);
print(a);
int loc = Arrays.binarySearch(a, a[3]);
System.out.println("Location of " + a[3] +
" = " + loc);
}
} ///:~
Of course, your compareTo( ) method can be as complex as necessary.
Lists
A List can be sorted and searched in the same fashion as an array. The static methods to sort and search a List are contained in the class Collections, but they have similar signatures as the ones in Arrays: sort(List) to sort a List of objects that implement Comparable, binarySearch(List, Object) to find an object in the list, sort(List, Comparator) to sort a List using a Comparator, and binarySearch(List, Object, Comparator) to find an object in 322
Thinking in Java
www.BruceEckel.com
that list.9 This example uses the previously-defined CompClass and AlphaComp to demonstrate the sorting tools in Collections:
//: ListSort.java
// Sorting and searching Lists with 'Collections'
package c08.newcollections;
import java.util.*;
public class ListSort {
public static void main(String[] args) {
final int SZ = 20;
// Using "natural comparison method":
List a = new ArrayList();
for(int i = 0; i < SZ; i++)
a.add(new CompClass(
(int)(Math.random() *100)));
Collection1.print(a);
Collections.sort(a);
Collection1.print(a);
Object find = a.get(SZ/2);
int loc = Collections.binarySearch(a, find);
System.out.println("Location of " + find +
" = " + loc);
// Using a Comparator:
List b = new ArrayList();
for(int i = 0; i < SZ; i++)
b.add(Array1.randString(4));
Collection1.print(b);
AlphaComp ac = new AlphaComp();
Collections.sort(b, ac);
Collection1.print(b);
find = b.get(SZ/2);
// Must use the Comparator to search, also:
loc = Collections.binarySearch(b, find, ac);
System.out.println("Location of " + find +
" = " + loc);
}
} ///:~
The use of these methods is identical to the ones in Arrays, but you’re using a List instead of an array.
The TreeMap must also order its objects according to Comparable or Comparator.
Utilities
There are a number of other useful utilities in the Collections class:

9 At the time of this writing, a Collections.stableSort( ) had been announced, to perform a merge sort, but it was unavailable for testing.
Chapter 8: Holding Your Objects 323 enumeration(Collection)
Produces an old-style
Enumeration for the argument.
max(Collection)
Produces the maximum or
min(Collection)
minimum element in the argument
using the natural comparison
method of the objects in the
Collection.
max(Collection, Comparator)
Produces the maximum or
min(Collection, Comparator)
minimum element in the
Collection using the Comparator.
nCopies(int n, Object o)
Returns an immutable List of size
n whose handles all point to o.
subList(List, int min, int max)
Returns a new List backed by the
specified argument List that is a
window into that argument with
indexes starting at min and
stopping just before max.
Note that min( ) and max( ) work with Collection objects, not with Lists, so you don’t need to worry about whether the Collection should be sorted or not. (As mentioned earlier, you do need to sort( ) a List or an array before performing a binarySearch( ).) Making a C
Collection or M
Map unmodifiable