Java将类型化列表转换为数组

Question

这是我的方法

public AuctionItem[] getOpenAuctions() throws RemoteException {

    return itemList.toArray((AuctionItem[]) java.lang.reflect.Array
            .newInstance(itemList.getClass(), itemList.size()));

}

这是我的错误

Exception in thread "main" java.lang.ClassCastException: [Ljava.util.LinkedList; cannot be cast to [LAuction.AuctionItem;
at Auction.AuctionImpl.getOpenAuctions(AuctionImpl.java:44)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at sun.rmi.server.UnicastServerRef.dispatch(Unknown Source)
at sun.rmi.transport.Transport$1.run(Unknown Source)
at sun.rmi.transport.Transport$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at sun.rmi.transport.Transport.serviceCall(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source)
at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source)
at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
at sun.rmi.server.UnicastRef.invoke(Unknown Source)
at java.rmi.server.RemoteObjectInvocationHandler.invokeRemoteMethod(Unknown Source)
at java.rmi.server.RemoteObjectInvocationHandler.invoke(Unknown Source)
at $Proxy0.getOpenAuctions(Unknown Source)
at Seller.SellerMain.main(SellerMain.java:38)

怎么了

Answer 1

试试看：

return itemList.toArray(new AuctionItem[itemList.size()]);

您编写的代码的问题是itemList.getClass()返回类LinkedList。所以Array.newInstance()方法正在创建一个LinkedList[]，然后您尝试将其类型转换为一个AuctionItem[]。因为这两种类型对于赋值不兼容，所以它抛出一个ClassCastException

Answer 2

itemList.getClass()返回LinkedList.class，因为它是一个LinkedListitemList.peek().getClass()将修复此问题，但前提是列表至少有一个元素

为什么不只是：

public AuctionItem[] getOpenAuctions() {
    return itemList.toArray(new AuctionItem[itemList.size()]);
}