Java编程思想: 容器深入研究

为什么80%的码农都做不了架构师？>>>   

完整的容器分类法

 

填充容器

进行容器的填充时, 我们可以使用Collections.nCopies()来创建一个List, 或者使用fill来进行填充.

import java.util.*;

class StringAddress {
  private String s;
  public StringAddress(String s) {this.s = s;}
  public String toString() {
    return super.toString() + " " + s;
  }

}
public class FillingLists {
  public static void main(String[] args) {
    List<StringAddress> list = new ArrayList<>(Collections.nCopies(4, new StringAddress("Hello")));
    // [[e-mail] Hello, [e-mail] Hello, [e-mail] Hello, [e-mail] Hello]
    System.out.println(list);
    Collections.fill(list, new StringAddress("World"));
    // [[e-mail] World, [e-mail] World, [e-mail] World, [e-mail] World]
    System.out.println(list);
  }
}

一种Generator解决方案

我们可以定义一个生成器来进行容器的操作:

import java.util.*;

interface Generator<T> {
  T next();
}

class CollectionData<T> extends ArrayList<T> {
  public CollectionData(Generator<T> gen, int quantity) {
    for (int i = 0; i < quantity; i++) {
      add(gen.next());
    }
  }
  public static <T> CollectionData<T> list(Generator<T> gen, int quantity) {
    return new CollectionData<>(gen, quantity);
  }
}

class Government implements Generator<String> {
  String[] foundation = ("strange women lying in ponds distributing swords is no basis for a system of government").split(" ");
  private int index;
  public String next() { return foundation[index++]; }
}
public class CollectionDataTest {
  public static void main(String[] args) {
    Set<String> set = new LinkedHashSet<>(new CollectionData<>(new Government(), 15));
    System.out.println(set);
    set.addAll(CollectionData.list(new Government(), 15));
    System.out.println(set);
  }
}

Map生成器

import java.util.LinkedHashMap;

class Pair<K, V> {
  public final K key;
  public final V value;
  public Pair(K k, V v) {
    key = k;
    value = v;
  }
}

public class MapData<K, V> extends LinkedHashMap<K, V> {
  public MapData(Generator<Pair<K, V>> gen, int quantity) {
    for (int i = 0; i < quantity; i++) {
      Pair<K, V> p = gen.next();
      put(p.key, p.value);
    }
  }

  public MapData(Generator<K> genK, Generator<V> genV, int quantity) {
    for (int i = 0; i < quantity; i++) {
      put(genK.next(), genV.next());
    }
  }

  public MapData(Generator<K> genK, V value, int quantity) {
    for (int i = 0; i < quantity; i++) {
      put(genK.next(), value);
    }
  }

  public MapData(Iterable<K> genK, Generator<V> genV) {
    for (K key: genK) {
      put(key, genV.next());
    }
  }

  public MapData(Iterable<K> genK, V value) {
    for (K key: genK) {
      put(key, value);
    }
  }

  public static <K, V> MapData<K, V> map(Generator<Pair<K, V>> gen, int quantity) {
    return new MapData<K, V>(gen, quantity);
  }
  public static <K, V> MapData<K, V> map(Generator<K> genK, Generator<V> genV, int quantity) {
    return new MapData<K, V>(genK, genV, quantity);
  }
  public static <K, V> MapData<K, V> map(Generator<K> genK, V value, int quantity) {
    return new MapData<K, V>(genK, value, quantity);
  }
  public static <K, V> MapData<K, V> map(Iterable<K> genK, Generator<V> genV) {
    return new MapData<K, V>(genK, genV);
  }
  public static <K, V> MapData<K, V> map(Iterable<K> genK, V value) {
    return new MapData<K, V>(genK, value);
  }
}

我们可以使用封装好的MapData类:

import java.util.*;

class Letters implements Generator<Pair<Integer, String>>, Iterable<Integer> {
  private int size = 9;
  private int number = 1;
  private char letter = 'A';
  public Pair<Integer, String> next() {
    return new Pair<Integer, String>(number++, "" + letter);
  }
  public Iterator<Integer> iterator() {
    return new Iterator<Integer>() {
      public Integer next() { return number++; }
      public boolean hasNext() { return number < size; }
      public void remove() {
        throw new UnsupportedOperationException();
      }
    };
  }
}
public class MapDataTest {
  public static void main(String[] args) {
    // {1=A, 2=A, 3=A, 4=A, 5=A, 6=A, 7=A, 8=A, 9=A, 10=A, 11=A}
    System.out.println(MapData.map(new Letters(), 11));
  }
}

使用Abstract类

我们可以通过继承其Abstract类来定制Map,Set等.

转载于:https://my.oschina.net/voler/blog/724266