Java：这两个代码是一样的吗？(Java: Are these 2 codes the same?)

Java：这两个代码是一样的吗？(Java: Are these 2 codes the same?) for (Player p : players) { p.addCard(deck.dealCard()); p.addCard(deck.dealCard()); }

和

for (int i = 0; i < players.size() ; i++) { Player p = players.get(i); p.addCard(deck.dealCard()); p.addCard(deck.dealCard()); }

第二个代码会产生一个空指针异常，可以做些什么来使底部等价？

for (Player p : players) { p.addCard(deck.dealCard()); p.addCard(deck.dealCard()); }

and

for (int i = 0; i < players.size() ; i++) { Player p = players.get(i); p.addCard(deck.dealCard()); p.addCard(deck.dealCard()); }

The second code yeilds a null pointer exception, what can be done to make the bottom one equivalent ?

最满意答案

如果players是自定义java.lang.Iterable ，那么get()实现被破坏，或者无论如何，都会以意想不到的方式行为（与java.util.List的行为不同），我可以看到发生这种情况。

除此之外，我能想到的唯一事情就是你没有在你的代码中显示我们的东西会导致某些错误。

如果你这样做会发生什么？

for (Iterator<Player> playerIter = players.iterator(); playerIter.hasNext();) { Player p = playerIter.next(); p.addCard(deck.dealCard()); p.addCard(deck.dealCard()); }

编辑：

只要阅读AZ的回应 ，它肯定有可能是size()也有奇怪的行为。

I can see this happening if players is a custom java.lang.Iterable who's get() implementation is broken, or at any rate, behaves in an unexpected manner (different from java.util.List's behavior).

Other that that, the only thing I can think of is that something you're not showing us in your code is causing something to go terribly wrong.

What happens if you do this?

for (Iterator<Player> playerIter = players.iterator(); playerIter.hasNext();) { Player p = playerIter.next(); p.addCard(deck.dealCard()); p.addCard(deck.dealCard()); }

Edit:

Just read AZ's response, and it's definitely possible that it's size() that has the odd behavior as well.