java - 如何制作参数化方法？

Question

我有类似的类来制作产品工厂:

package com.nda.generics;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

import com.nda.generics.Sizeable.Size;

public class ProductFactory{

        private Collection<? extends Sizeable> sources;

        public ProductFactory(Collection<? extends Sizeable> sources) {
            this.sources=sources;
        }

        public void setSources(Collection<? extends Sizeable> sources) {
            this.sources=sources;
        }

        public Collection<Product> makeProductList() {

            Collection<Product> products=new ArrayList<Product>();

            for (Sizeable item:sources) {

                switch(item.getSize()) {

                    case BIG: products.add(new Sausage()); break;
                    case MIDDLE: products.add(new Feets()); break;
                    case LITTLE: products.add(new Conservative()); break;
                }
            }

            return products;
        }

        public class Conservative extends Product {

            private Conservative(){}
        }

        public class Feets extends Product {

            private Feets(){}
        }

        public class Sausage extends Product {

            private Sausage(){}
        }
    }

这家工厂使用动物的大小制作产品 list 。但我还需要参数化我将设置产品类型的方法/类，例如新的脚(使用构造函数的参数)。我该怎么做？谢谢。

Answer 1

我相信这就是您正在寻找的......

public <T extends Product> T getNewProduct(Class<T> productClass, String param1, int param2) {

   T product = productClass.newInstance();

   // Assuming your abstract Product class defines these setters
   product.setStringParam(param1);
   product.setIntParam(param2);

   return product;
 }

然后你就可以这样调用......

// Assuming you want a Feet object....
Feet feet = productFactoryInstance.getNewProduct(Feet.class, "productParam1", productParam2);

此外，作为旁注，您应该将 ProductFacotry 设置为单例。你不需要多个，它可以避免很多其他的头痛，你可以像这样......

// Make ProductFacotry constructor private so you don't call "new" all over the place
private ProductFactory() {}

// Variable to hold your only instance of product factory (hence, singleton name...)
private static ProductFactory INSTANCE = null;

public static synchronized Get() {
  if(INSTANCE == null) {
    // You can call the constructor here, even though its private since you're
    // inside the same class
    INSTANCE = new ProductFactory();
  }

  return INSTANCE;
}

然后，每当您想使用它来获取产品时，只需执行此操作...

Feet feet = ProductFactory.Get().getNewProduct(Feet.class, "productParam1", productParam2);