总结 03- 代码重构

public class SorterFactory {
  public static <T> Sorter<T> getSorter() {
  	return new BubbleSorter<T>();
  } 
}
public class Client {
  public static void main(String[] args) {
    Integer[] array = { 5, 4, 9, 7, 6, 3, 8, 1, 0, 2 };
    Sorter<Integer> sorter = SorterFactory.getSorter();
    Sortable<Integer> sortable = SortableFactory.getSortable(array);
    Comparator<Integer> comparator = ComparatorFactory.getComparator();
    sorter.sort(sortable, comparator);
    ……
  } 
}

class SorterFactory_2 {
  @SuppressWarnings("unchecked")
  public static <T> Sorter<T> getSorter(String implClass) {
    try {
    Class impl = Class.forName(implClass);
    return (Sorter<T>) impl.newInstance();
    } catch (Exception e) {
    throw new IllegalArgumentException(
    "Illegal class name: " + implClass, e);
    } 
  }
}
Sorter<Integer> sorter = 
SorterFactory_2.getSorter("demo.sort.impl.BubbleSorter");

class SorterFactory_3 {
  private final static Properties IMPLS = loadImpls();
  private static Properties loadImpls() {
    Properties defaultImpls = new Properties();
    Properties impls = new Properties(defaultImpls);
    defaultImpls.setProperty("sorter",
    "demo.sort.impl.BubbleSorter");
    try {
    impls.load(SorterFactory_3.class.getResourceAsStream("sort.properties"));
    } catch (IOException e) {
    	throw new RuntimeException(e);
    }
    return impls; 
  }
  @SuppressWarnings("unchecked")
  public static <T> Sorter<T> getSorter() {
    String implClassName = IMPLS.getProperty("sorter");
    try {
    	Class implClass = Class.forName(implClassName);
    	return (Sorter<T>) implClass.newInstance();
    } catch (Exception e) {
    	throw new IllegalArgumentException("Illegal class name: " + implClassName, e);
    } 
  } 
}