泛型的覆盖方法(Overriding method with Generics)

 我有一个名为GenericOrder的基类，可以用来创建任何类型的产品的订单，然后我有更具体的订单的子类。 我的问题是与我的ComputerOrder类和我重写的方法。 这是基类代码。 
 
import java.util.List;
import java.util.ArrayList;

public class GenericOrder<T> {

private long orderNumber;
private List<T> products;
private T theClass;

public GenericOrder() 
{
    products = new ArrayList<T>();
    orderNumber = System.currentTimeMillis();
}

public long getOrderNumber() {
    return orderNumber;
}

public void addProduct(T newProduct) {
    products.add(newProduct);

}

public int getNumberOfProducts() {
    return products.size();
}

public List<T> getProducts()
{
    return products;
}

public void setProducts(List<T> products)
{
    this.products = products;
}

public T get()
{
    return theClass;
}

public void set(T theClass)
{
    this.theClass = theClass;
}
}
 
 这是我的子类代码。 getProducts是我遇到麻烦的方法。 
 
import java.util.ArrayList;
import java.util.List;

public class ComputerOrder<T> extends GenericOrder<T> {
    private List<ComputerPart> computerParts = new ArrayList<ComputerPart>();
    private String orderType = "Computer Parts";

public ComputerOrder() {
    super();

}

public void addProduct(ComputerPart newProduct) {

    computerParts.add(newProduct);

}

public String getOrderType() {
    return orderType;
}

public int getNumberOfProducts() {
    return computerParts.size();
}


public List<T> getProducts()
{

    return computerParts;
}


}
 
 我得到的错误说不能从List(ComputerPart)转换为List<T> 

I have a base class called GenericOrder that can be used to create an order with any type of products, then I have subclasses of that order that are more specific. My problem is with my ComputerOrder class and a method that I'm overriding. Here's the base class code. 
 
import java.util.List;
import java.util.ArrayList;

public class GenericOrder<T> {

private long orderNumber;
private List<T> products;
private T theClass;

public GenericOrder() 
{
    products = new ArrayList<T>();
    orderNumber = System.currentTimeMillis();
}

public long getOrderNumber() {
    return orderNumber;
}

public void addProduct(T newProduct) {
    products.add(newProduct);

}

public int getNumberOfProducts() {
    return products.size();
}

public List<T> getProducts()
{
    return products;
}

public void setProducts(List<T> products)
{
    this.products = products;
}

public T get()
{
    return theClass;
}

public void set(T theClass)
{
    this.theClass = theClass;
}
}
 
And here is my subClass code. The getProducts is the method I'm having trouble with. 
 
import java.util.ArrayList;
import java.util.List;

public class ComputerOrder<T> extends GenericOrder<T> {
    private List<ComputerPart> computerParts = new ArrayList<ComputerPart>();
    private String orderType = "Computer Parts";

public ComputerOrder() {
    super();

}

public void addProduct(ComputerPart newProduct) {

    computerParts.add(newProduct);

}

public String getOrderType() {
    return orderType;
}

public int getNumberOfProducts() {
    return computerParts.size();
}


public List<T> getProducts()
{

    return computerParts;
}


}
 
The Error I get says cannot convert from List(ComputerPart) to List<T>

原文：https://stackoverflow.com/questions/34315620