. headSet(E element) tailSet(E element, boolean inclusive) , element . inclusive true, .
NavigableSet.
/* # 13: c NavigableSet: NavigableSetTest.java */
package by.bsu.chapt10;
import java.util.*;
public class NavigableSetTest {
public static void main(String[] args) {
HashSet<String> city = new HashSet<String>();
city.add("Minsk");
city.add("Mosow");
city.add("Polotsk");
city.add("Brest");
NavigableSet<String> ns = new TreeSet<String>(city);
System. out. println("All: " + ns);
System. out. println("Between Minsk and Polotsk: "
+ ns.subSet("Minsk","Polotsk"));
System. out. println("Before Minsk: "
+ ns.headSet("Minsk"));
System. out. println("After Minsk: "
+ ns.tailSet("Minsk", false));
}
}
:
All: [Brest, Minsk, Mosow, Polotsk]
Between Minsk and Polotsk: [Minsk, Mosow]
Before Minsk: [Brest]
After Minsk: [Mosow, Polotsk]
, -. () , . - hashCode() equals() . , null.
:
AbstractMap<K,V> Map<K,V>;
HashMap<K,V> AbstractMap<K,V>, -, -;
TreeMap<K,V> AbstractMap<K,V>, , .
WeakHashMap<K,V> , .
LinkedHashMap<K,V> . , - .
. 3.
IdentityHashMap<K,V> - - System.identityHashCode() , hashCode(), .
:
Map<K,V> ;
Map.Entry<K,V> -;
SortedMap<K,V> ;
NavigableMap<K,V> .
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Map<K,V> :
void clear() ;
boolean containsKey(Object key) true, key ;
boolean containsValue(Object value) true, value ;
Set<Map.Entry<K,V>> entrySet() , ;
Set<K> keySet() ;
V get(Object obj) , obj;
V put(K key, V value) key value . . ;
void putAll(Map <? extends K,? extends V> t) t ;
V remove(Object key) - key;
Collection<V> values() , .
Map.Entry<K,V> :
K getKey() ;
V getValue() ;
V setValue(V obj) obj .
-
.
/* # 14: - :
DemoHashMap.java */
package chapt10;
import java.util.*;
public class DemoHashMap {
public static void main(String[] args){
HashMap<Integer, String> hm =
new HashMap<Integer, String>(5);
for (int i = 11; i < 15; i++) {
hm.put(i, i + "EL");
}
System. out. println(hm);
hm.put(12, "14EL");
System. out. println(hm + " ");
String a = hm.get(12);
System. out. println(a + " - '12'");
/* -
Map.Entry<K,V> */
Set<Map.Entry<Integer, String>> setvalue =
hm.entrySet();
System. out. println(setvalue);
Iterator<Map.Entry<Integer, String>> i =
setvalue.iterator();
while (i.hasNext()) {
Map.Entry<Integer, String> me = i.next();
System. out. print(me.getKey()+": ");
System. out. println(me.getValue());
}
}
}
{13=13EL, 14=14EL, 12=12EL, 11=11EL}
{13=13EL, 14=14EL, 12=14EL, 11=11EL}
14EL - '12'
[13=13EL, 14=14EL, 12=14EL, 11=11EL]
EL
EL
EL
EL
, HashMap<K,V> Map.Entry<K,V> .
/* # 15: :
DemoSecurity.java */
package chapt10;
import java.util.*;
public class DemoSecurity {
public static void main(String[] args) {
CheckRight. startUsing (2041, "");
CheckRight. startUsing (2420, "");
/*
*
*
*/
CheckRight. startUsing (2437, "");
CheckRight. startUsing (2041, "");
}
}
/* # 16: : CheckRight.java */
package chapt10;
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import java.util.*;
public class CheckRight {
private static HashMap<Integer, String> map =
new HashMap<Integer, String> ();
public static void startUsing(int id, String name) {
if (canUse(id)){
map.put(id, name);
System. out. println(" ");
} else {
System. out. println(" ");
}
}
public static boolean canUse(int id) {
final int MAX_NUM = 2; // 2 3
int currNum = 0;
if (!map.containsKey(id))
currNum = map.size();
return currNum < MAX_NUM;
}
}
:
,
. MAX_NUM , 2, .
EnumMap<K extends Enum<K>, V> , enum, . .
/* # 17: EnumMap: UseEnumMap.java */
package chapt10;
import java.util.EnumMap;
enum User {
STUDENT, TUTOR, INSTRUCTOR, DEAN
}
class UserPriority {
private int priority;
public UserPriority(User k) {
switch (k) {
case STUDENT:
priority = 1; break;
case TUTOR:
priority = 3; break;
case INSTRUCTOR:
priority = 7; break;
case DEAN:
priority = 10; break;
default:
priority = 0;
}
}
public int getPriority() {
return priority;
}
}
public class UseEnumMap {
public static void main(String[] args) {
EnumMap<User, UserPriority> faculty =
new EnumMap<User, UserPriority> (User. class);
for (User user: User.values()) {
faculty.put(user,
new UserPriority(user));
}
for (User user: User.values()) {
System. out. println(user.name()
+ "-> Priority:" +
((UserPriority) faculty.get(user)).getPriority());
}
}
}
:
STUDENT-> Priority:1
TUTOR-> Priority:3
INSTRUCTOR-> Priority:7
DEAN-> Priority:10
NavigableMap<K, V>
NavigableSet, , , , "-":
Map.Entry<K,V> lowerEntry(K key);
Map.Entry<K,V> floorEntry(K key);
Map.Entry<K,V> higherEntry(K key);
Map.Entry<K,V> ceilingEntry(K key);
K lowerKey(K key);
K floorKey(K key);
K higherKey(K key);
K ceilingKey(K key);
pollFirstEntry pollLastEntry , . firstEntry lastEntry , .
Map.Entry<K,V> pollFirstEntry();
Map.Entry<K,V> pollLastEntry();
Map.Entry<K,V> firstEntry();
Map.Entry<K,V> lastEntry();
, :
NavigableMap<K,V> descendingMap();
, , :
NavigableSet navigableKeySet();
NavigableSet descendingKeySet();
, , , . NavigableSet, , . , , , .
NavigableMap<K,V> subMap(K fromKey, boolean fromInclusive, K toKey, boolean toInclusive);
NavigableMap<K,V> headMap(K toKey, boolean inclusive);
NavigableMap<K,V> tailMap(K fromKey, boolean inclusive);
SortedMap<K,V> subMap(K fromKey, K toKey);
SortedMap<K,V> headMap(K toKey);
SortedMap<K,V> tailMap(K fromKey);
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, , , , , Java , Hashtable<K,V>, Vector<E> ( ) Enumeration<E>. , .
Hashtable<K,V> Map, :
Enumeration<V> elements() ;
Enumeration<K> keys() .
/* # 18: - :
HashTableDemo.java */
package by.bsu.chapt10;
import java.util.*;
import java.io.*;
public class HashTableDemo {
public static void main(String[] args) {
Hashtable<Integer, Double> ht =
new Hashtable<Integer, Double>();
for (int i = 0; i < 5; i++) {
ht.put(i, Math. atan (i));
}
Enumeration<Integer> ek = ht.keys();
int key;
while (ek.hasMoreElements()) {
key = ek.nextElement();
System. out. printf("%4d ", key);
}
System. out. println("");
Enumeration<Double> ev = ht.elements();
double value;
while (ev.hasMoreElements()) {
value = ev.nextElement();
System. out. printf("%.2f ", value);
}
}
}
:
4 3 2 1 0
1,33 1,25 1,11 0,79 0,00
, , .
Collections
Collections , . , , , , . Collections : public static <E> Collection <E> checkedCollection(Collection<E> c, Class<E> type) , ,
ClassCastException:
/* # 19: : SafeSet.java */
package by.bsu.chapt10;
import java.util.*;
public class SafeSet {
public static void main(String args[]) {
//HashSet c = new HashSet();
HashSet c = Collections. checkedSet (
new HashSet<String>(), String. class);
c.add("Java");
c.add(7.0); //
}
}
, , : checkedList(),
checkedSortedMap(), checkedMap(), checkedSortedSet(),
checkedCollection(), :
<T> boolean addAll(Collection<? super T> c, T... a) ;
<T> void copy(List<? super T> dest, List<? extends T> src) ;
boolean disjoint(Collection<?> c1, Collection<?> c2) true, ;
<T> List <T> emptyList(), <K,V> Map <K,V> emptyMap(),
<T> Set <T> emptySet() ,
;
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<T> void fill(List<? super T> list, T obj) ;
int frequency(Collection<?> c, Object o) ;
<T extends Object & Comparable <? super T>> T max(Collection<? extends T> coll),
<T extends Object & Comparable <? super T>> T min(Collection<? extends T> coll)
;
<T> T max(Collection <? extends T> coll,
Comparator<? super T> comp),
<T> T min(Collection<? extends T> coll,
Comparator<? super T> comp) , Comparator ;
<T> List <T> nCopies(int n, T o) n ;
<T> boolean replaceAll(List<T> list, T oldVal, T newVal) ;
void reverse(List<?> list) ;
void rotate(List<?> list, int distance) ;
void shuffle(List<?> list) ;
<T> Set <T> singleton(T o), singletonList(T o), singletonMap(K key, V value) , , ;
<T extends Comparable<? super T>> void sort(List<T> list),
<T> void sort(List<T> list, Comparator<? super T> c) , Comparator ;
void swap(List<?> list, int i, int j) .
/* # 20: Collections: CollectionsDemo.java:
MyComparator.java */
package by.bsu.chapt10;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class CollectionsDemo {
public static void main(String[] args) {
MyComparator<Integer> comp =
new MyComparator<Integer>();
ArrayList<Integer> list =
new ArrayList<Integer>();
Collections. addAll (list, 1, 2, 3, 4, 5);
Collections. shuffle (list);
print(list);
Collections. sort (list, comp);
print(list);
Collections. reverse (list);
print(list);
Collections. rotate (list, 3);
print(list);
System. out. println("min: "
+ Collections.min(list, comp));
System. out. println("max: "
+ Collections.max(list, comp));
List<Integer> singl =
Collections.singletonList(71);
print(singl);
//singl.add(21);//
}
static void print(List<Integer> c) {
for (int i: c)
System.out.print(i + " ");
System.out.println();
}
}
package chapt10;
import java.util.Comparator;
public class MyComparator<T> implements Comparator<Integer> {
public int compare(Integer n, Integer m) {
return m.intValue() - n.intValue();
}
}
:
4 3 5 1 2
5 4 3 2 1
1 2 3 4 5
3 4 5 1 2
min: 5
max: 1
Arrays
java.util Arrays, , , , , :
static int binarySearch( ) . ;
static void fill( ) ;
static void sort( ) Comparator ;
static <T> T[] copyOf(T[] original, int newLength) , null ;
static <T> T[] copyOfRange(T[] original, int from, int to) ;
static boolean equals( 1, 2 ) ;
static boolean deepEquals( Object[] a1, Object[] a2 ) ;
static String deepToString( Object[] a ) ;
static int deepHashCode( Object[] a ) - ;
static <T> List<T> asList(T... a) , List<T>.
.
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/* # 21: Arrays: ArraysEqualDemo.java */
package chapt10;
import java.util.*;
public class ArraysEqualDemo {
public static void main(String[] args) {
char m1[] = new char [3];
char m2[] = { 'a', 'b', 'c' };
char i;
Arrays. fill (m1, 'a');
System. out. print(" m1:");
for (i = 0; i < 3; i++) {
System. out. print(" " + m1[i]);
}
m1[1] = 'b';
m1[2] = 'c';
//m1[2]='x'; //
if (Arrays. equals (m1, m2))
System. out. print("\nm1 m2 ");
Else
System. out. print("\nm1 m2 ");
m1[0] = 'z';
Arrays.sort(m1);
System. out. print("\n m1:");
for (i = 0; i < 3; i++)
System. out. print(" " + m1[i]);
System. out. print(
"\n 'c' -"
+ Arrays. binarySearch (m1, 'c'));
Integer arr[] = {35, 71, 92};
//
System. out. println(Arrays. deepToString (arr));
// -
System. out. println(Arrays. deepHashCode (arr));
Integer arr2[] = {35, 71, 92};
//
System. out. println(Arrays. deepEquals (arr, arr2));
char m3[] = new char [5];
//
m3 = Arrays. copyOf (m1, 5);
System. out. print(" m3:");
for (i = 0; i < 5; i++) {
System. out. print(" " + m3[i]);
}
}
}
:
m1: a a a
M1 m2
m1: b c z
'c' 1
[35, 71, 92]
True
m3: b c z □ □
