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;
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
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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 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 checkedCollection(): public static <E> Collection <E> checkedCollection(Collection<E> c, Class<E> type) , ,
ClassCastException:
/* # 19: : SafeCollection.java */
package chapt10;
import java.util.*;
public class SafeCollection {
public static void main(String args[]) {
Collection c = Collections.checkedCollection(
new HashSet<String>(), String. class);
c.add("Java");
c.add(7.0); //
}
}
, , : checkedList(),
checkedSortedMap(), checkedMap(), checkedSortedSet(),
checkedSet(), :
<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 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, , , , , :
int binarySearch( ) . ;
void fill( ) ;
void sort( ) Comparator ;
static <T> T[] copyOf(T[] original, int newLength) , null ;
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static <T> T[] copyOfRange(T[] original, int from, int to) ;
<T> List<T> asList(T... a) , List<T>.
.
/* # 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' }, 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 □ □
10
A
1. , . .
2. , . , .
3. .
4. .
5. . .
6. . .
7. , .
8. . .
9. (, ) I(1..n) U(1..n) n- R. R .
10. : , .. , .
11. , HashMap.
12. , .
13. , , .
14. , ArrayList. , sort() Collections.
|
|
|
15. , '(', ')', '[', ']', '{', '}'. . .
16. . . , , . HashSet.
17. . . . , , . HashMap.
B
1. N , 1 N. , . , . ArrayList, LinkedList. ? ?
2. X. , , , X, , X.
3. , . . PriorityQueue.
4. Graph, . . .
5. :
/ ;
, (.. ).
6. , N- . , . , .
7. . , . , : ) S = A + B; ) P = A * B.
8. . C1, , . C1, .
9. ; . C1 2, 1- 2- , . C1 2 , .
10. , . . , , , , , . . .
11. , , , K1 K2. , K1 K2 . , , , 1 2 20- ( ).
12. N . , . , . HashMap.
13. . , , . PriorityQueue.
14. N . , . TreeMap.
15. . , . ,
. , , 90 , . HashSet.
|
|
|
16. . , . Stack.
17. " ", K, . K- .
18. N , . , .
19. N , . K .
10
10.1.
, ?
1) Set;
2) List;
3) Map;
4) Vector;
5) .
10.2.
ArrayList ?
1) ArrayList a = new ArrayList(); a.add(0);
2) ArrayList a = new ArrayList(); a[0]=0;
3) List a = new List(); a.add(0);
4) List a = new ArrayList(10); a.add(0);
10.3.
Hashtable?
1) Set;
2) Vector;
3) AbstractMap;
4) List;
5) Map.
10.4.
:
import java.util.*; class Quest4 { public static void main (String args[]) { Object ob = new HashSet();System.out.print((ob instanceof Set) + ", ");System.out.print(ob instanceof SortedSet);}}?
1) true, false;
2) true, true;
3) false, true;
4) false, false;
5) .
10.5.
java.util?
1) SortedMap;
2) HashMap;
3) HashSet;
4) SortedSet;
5) Stack;
6) AbstractMap.
Java , , (, , .), . Java :
AWT( java.awt) , . , .
Swing ( javax.swing, javax , , ) , AWT. J (JButton, JLabel
..). JFC (Java Foundation Classes), JavaBeans, .
Swing, AWT, - . Swing , , . , Swing , .
Java . , Web- Web-. .
, Panel, , Frame, Window.
AWT Swing, , 11.1.
java.awt.Component , . , .
. 11.1. AWT Swing
Container add(), () , . Container Panel Window .
