Java集合(2):两个生成器的例子:Collection生成器CollectionData及Map生成器MapData

Collection生成器CollectionData

CollectionData体现了适配器模式的设计思想,它能把实现Generator接口的类的对象(包括上一章数组中的各种RandomGenerator)都复制到自身当中。

 1 import java.util.ArrayList;
 2 import java.util.LinkedHashSet;
 3 import java.util.Set;
 4 
 5 interface Generator<T> {
 6     T next();
 7 }
 8 
 9 class CollectionData<T> extends ArrayList<T> {
10     private static final long serialVersionUID = 1L;
11     public CollectionData(Generator<T> gen, int quantity) {
12         for (int i = 0; i < quantity; i++)
13             add(gen.next());
14     }
15     public static <T> CollectionData<T> list(Generator<T> gen, int quantity) {
16         return new CollectionData<T>(gen, quantity);
17     }
18 }
19 
20 class Animal implements Generator<String> {
21     private String[] items = { "Dog", "Pig", "Cat" };
22     private int index;
23     @Override
24     public String next() {
25         return items[index++];
26     }
27 }
28 
29 public class Test2 {
30     public static void main(String[] args) {
31         Set<String> set = new LinkedHashSet<String>(new CollectionData<String>(new Animal(), 3));
32         System.out.println(set); // [Dog, Pig, Cat]
33         set.addAll(CollectionData.list(new Animal(), 3));
34         System.out.println(set); // [Dog, Pig, Cat]
35     }
36 }

 

Map生成器MapData

我们可以使用同样的方式生成Map,我们可以Generator<K>,Generator<V>分开生成,也可以使用Pair<K, V>组装好K,V再生成。

  1 import java.util.Iterator;
  2 
  3 import java.util.LinkedHashMap;
  4 
  5 class Pair<K, V> {
  6     public final K key;
  7     public final V value;
  8 
  9     public Pair(K k, V v) {
 10         this.key = k;
 11         this.value = v;
 12     }
 13 }
 14 
 15 class MapData<K, V> extends LinkedHashMap<K, V> {
 16     private static final long serialVersionUID = 1L;
 17 
 18     // A single Pair Generator:
 19     public MapData(Generator<Pair<K, V>> gen, int quantity) {
 20         for (int i = 0; i < quantity; i++) {
 21             Pair<K, V> p = gen.next();
 22             put(p.key, p.value);
 23         }
 24     }
 25 
 26     public static <K, V> MapData<K, V> map(Generator<Pair<K, V>> gen, int quantity) {
 27         return new MapData<K, V>(gen, quantity);
 28     }
 29 
 30     // Two separate Generators:
 31     public MapData(Generator<K> genK, Generator<V> genV, int quantity) {
 32         for (int i = 0; i < quantity; i++) {
 33             put(genK.next(), genV.next());
 34         }
 35     }
 36 
 37     public static <K, V> MapData<K, V> map(Generator<K> genK, Generator<V> genV, int quantity) {
 38         return new MapData<K, V>(genK, genV, quantity);
 39     }
 40 
 41     // A key Generator and a single value:
 42     public MapData(Generator<K> genK, V value, int quantity) {
 43         for (int i = 0; i < quantity; i++) {
 44             put(genK.next(), value);
 45         }
 46     }
 47 
 48     public static <K, V> MapData<K, V> map(Generator<K> genK, V value, int quantity) {
 49         return new MapData<K, V>(genK, value, quantity);
 50     }
 51 
 52     // An Iterable and a single value:
 53     public MapData(Iterable<K> genK, V value) {
 54         for (K key : genK) {
 55             put(key, value);
 56         }
 57     }
 58 
 59     public static <K, V> MapData<K, V> map(Iterable<K> genK, V value) {
 60         return new MapData<K, V>(genK, value);
 61     }
 62 }
 63 
 64 class Letters implements Generator<Pair<Integer, String>>, Iterable<Integer> {
 65     private int size = 9;
 66     private int number = 1;
 67     private char letter = 'A';
 68 
 69     @Override
 70     public Pair<Integer, String> next() {
 71         return new Pair<Integer, String>(number++, "" + letter++);
 72     }
 73 
 74     @Override
 75     public Iterator<Integer> iterator() {
 76         return new Iterator<Integer>() {
 77             @Override
 78             public Integer next() {
 79                 return number++;
 80             }
 81 
 82             @Override
 83             public boolean hasNext() {
 84                 return number < size;
 85             }
 86 
 87             @Override
 88             public void remove() {
 89                 throw new UnsupportedOperationException();
 90             }
 91         };
 92     }
 93 }
 94 
 95 public class Test3 {
 96     public static void main(String[] args) {
 97         // A single Pair Generator test
 98         MapData<Integer, String> data1 = MapData.map(new Letters(), 11);
 99         System.out.println(data1); // {1=A, 2=B, 3=C, 4=D, 5=E, 6=F, 7=G, 8=H, 9=I, 10=J, 11=K}
100         // An Iterable and a single value test
101         MapData<Integer, String> data2 = MapData.map(new Letters(), "Pop");
102         System.out.println(data2); // {1=Pop, 2=Pop, 3=Pop, 4=Pop, 5=Pop, 6=Pop, 7=Pop, 8=Pop}
103     }
104 }

 

posted @ 2018-02-08 18:29  Storm_L  阅读(1694)  评论(0编辑  收藏  举报