Java/Collections Data Structure/General Collections
Содержание
Collections: List, Set, SortedSet, LinkedHashSet, Map, LinkedHashMap
<source lang="java">
import java.util.ArrayList; import java.util.Collection; import java.util.HashMap; import java.util.HashSet; import java.util.Iterator; import java.util.LinkedHashMap; import java.util.LinkedHashSet; import java.util.LinkedList; import java.util.List; import java.util.Map; import java.util.Set; import java.util.SortedMap; import java.util.SortedSet; import java.util.TreeMap; import java.util.TreeSet; public class CollectionAll {
public static void main(String[] args) {
List list1 = new LinkedList();
list1.add("list");
list1.add("dup");
list1.add("x");
list1.add("dup");
traverse(list1);
List list2 = new ArrayList();
list2.add("list");
list2.add("dup");
list2.add("x");
list2.add("dup");
traverse(list2);
Set set1 = new HashSet();
set1.add("set");
set1.add("dup");
set1.add("x");
set1.add("dup");
traverse(set1);
SortedSet set2 = new TreeSet();
set2.add("set");
set2.add("dup");
set2.add("x");
set2.add("dup");
traverse(set2);
LinkedHashSet set3 = new LinkedHashSet();
set3.add("set");
set3.add("dup");
set3.add("x");
set3.add("dup");
traverse(set3);
Map m1 = new HashMap();
m1.put("map", "jexp");
m1.put("dup", "Kava2s");
m1.put("x", "Mava2s");
m1.put("dup", "Lava2s");
traverse(m1.keySet());
traverse(m1.values());
SortedMap m2 = new TreeMap();
m2.put("map", "jexp");
m2.put("dup", "Kava2s");
m2.put("x", "Mava2s");
m2.put("dup", "Lava2s");
traverse(m2.keySet());
traverse(m2.values());
LinkedHashMap /* from String to String */m3 = new LinkedHashMap();
m3.put("map", "jexp");
m3.put("dup", "Kava2s");
m3.put("x", "Mava2s");
m3.put("dup", "Lava2s");
traverse(m3.keySet());
traverse(m3.values());
}
static void traverse(Collection coll) {
Iterator iter = coll.iterator();
while (iter.hasNext()) {
String elem = (String) iter.next();
System.out.print(elem + " ");
}
System.out.println();
}
}
</source>
Simple demonstrations of the Collections utilities
<source lang="java">
// : c11:Utilities.java // Simple demonstrations of the Collections utilities. // From "Thinking in Java, 3rd ed." (c) Bruce Eckel 2002 // www.BruceEckel.ru. See copyright notice in CopyRight.txt. import java.util.ArrayList; import java.util.Arrays; import java.util.Collections; import java.util.ruparator; import java.util.Enumeration; import java.util.List; import java.util.Vector; public class Utilities {
public static void main(String[] args) {
List list = Arrays.asList("one Two three Four five six one".split(" "));
System.out.println(list);
System.out.println("max: " + Collections.max(list));
System.out.println("min: " + Collections.min(list));
AlphabeticComparator comp = new AlphabeticComparator();
System.out.println("max w/ comparator: " + Collections.max(list, comp));
System.out.println("min w/ comparator: " + Collections.min(list, comp));
List sublist = Arrays.asList("Four five six".split(" "));
System.out.println("indexOfSubList: "
+ Collections.indexOfSubList(list, sublist));
System.out.println("lastIndexOfSubList: "
+ Collections.lastIndexOfSubList(list, sublist));
Collections.replaceAll(list, "one", "Yo");
System.out.println("replaceAll: " + list);
Collections.reverse(list);
System.out.println("reverse: " + list);
Collections.rotate(list, 3);
System.out.println("rotate: " + list);
List source = Arrays.asList("in the matrix".split(" "));
Collections.copy(list, source);
System.out.println("copy: " + list);
Collections.swap(list, 0, list.size() - 1);
System.out.println("swap: " + list);
Collections.fill(list, "pop");
System.out.println("fill: " + list);
List dups = Collections.nCopies(3, "snap");
System.out.println("dups: " + dups);
// Getting an old-style Enumeration:
Enumeration e = Collections.enumeration(dups);
Vector v = new Vector();
while (e.hasMoreElements())
v.addElement(e.nextElement());
// Converting an old-style Vector
// to a List via an Enumeration:
ArrayList arrayList = Collections.list(v.elements());
System.out.println("arrayList: " + arrayList);
}
} ///:~ class AlphabeticComparator implements Comparator {
public int compare(Object o1, Object o2) {
String s1 = (String) o1;
String s2 = (String) o2;
return s1.toLowerCase().rupareTo(s2.toLowerCase());
}
} ///:~
</source>
Sometimes methods defined in the Collection interfaces don"t work
<source lang="java">
// : c11:Unsupported.java // Sometimes methods defined in the Collection interfaces don"t work! // {ThrowsException} // From "Thinking in Java, 3rd ed." (c) Bruce Eckel 2002 // www.BruceEckel.ru. See copyright notice in CopyRight.txt. import java.util.Arrays; import java.util.List; import java.util.ListIterator; public class Unsupported {
static List a = Arrays.asList("one two three four five six seven eight"
.split(" "));
static List a2 = a.subList(3, 6);
public static void main(String[] args) {
System.out.println(a);
System.out.println(a2);
System.out.println("a.contains(" + a.get(0) + ") = "
+ a.contains(a.get(0)));
System.out.println("a.containsAll(a2) = " + a.containsAll(a2));
System.out.println("a.isEmpty() = " + a.isEmpty());
System.out.println("a.indexOf(" + a.get(5) + ") = "
+ a.indexOf(a.get(5)));
// Traverse backwards:
ListIterator lit = a.listIterator(a.size());
while (lit.hasPrevious())
System.out.print(lit.previous() + " ");
System.out.println();
// Set the elements to different values:
for (int i = 0; i < a.size(); i++)
a.set(i, "47");
System.out.println(a);
// Compiles, but won"t run:
lit.add("X"); // Unsupported operation
a.clear(); // Unsupported
a.add("eleven"); // Unsupported
a.addAll(a2); // Unsupported
a.retainAll(a2); // Unsupported
a.remove(a.get(0)); // Unsupported
a.removeAll(a2); // Unsupported
}
} ///:~
</source>
Using the Collections.synchronized methods
<source lang="java">
// : c11:Synchronization.java // Using the Collections.synchronized methods. // From "Thinking in Java, 3rd ed." (c) Bruce Eckel 2002 // www.BruceEckel.ru. See copyright notice in CopyRight.txt. import java.util.ArrayList; import java.util.Collection; import java.util.Collections; import java.util.HashMap; import java.util.HashSet; import java.util.List; import java.util.Map; import java.util.Set; public class Synchronization {
public static void main(String[] args) {
Collection c = Collections.synchronizedCollection(new ArrayList());
List list = Collections.synchronizedList(new ArrayList());
Set s = Collections.synchronizedSet(new HashSet());
Map m = Collections.synchronizedMap(new HashMap());
}
} ///:~
</source>
