如何在 Java 中从 int 转换为 Long? [英] How do I convert from int to Long in Java?

问题描述

我一直发现在这里和 Google 的人都遇到了从 long 到 int 而不是相反的问题.然而，在从 int 变为 Long 之前，我确信我不是唯一遇到这种情况的人.

I keep finding both on here and Google people having troubles going from long to int and not the other way around. Yet I'm sure I'm not the only one that has run into this scenario before going from int to Long.

我发现的唯一其他答案是首先将其设置为 Long"，这确实没有解决问题.

The only other answers I've found were "Just set it as Long in the first place" which really doesn't address the question.

我最初尝试进行强制转换，但出现Cannot cast from int to Long"

I initially tried casting but I get a "Cannot cast from int to Long"

for (int i = 0; i < myArrayList.size(); ++i ) {
    content = new Content();
    content.setDescription(myArrayList.get(i));
    content.setSequence((Long) i);
    session.save(content);
}

正如你所想象的，我有点困惑，我一直在使用 int，因为有些内容是作为 ArrayList 进入的，而我所针对的实体m 存储此信息需要序列号为 Long.

As you can imagine I'm a little perplexed, I'm stuck using int since some content is coming in as an ArrayList and the entity for which I'm storing this info requires the sequence number as a Long.

推荐答案

请注意，转换为 long 和转换为 Long 之间存在差异.如果您强制转换为 long(原始值)，那么它应该自动装箱为 Long(包装它的引用类型).

Note that there is a difference between a cast to long and a cast to Long. If you cast to long (a primitive value) then it should be automatically boxed to a Long (the reference type that wraps it).

您也可以使用 new 来创建 Long 的实例，并使用 int 值对其进行初始化.

You could alternatively use new to create an instance of Long, initializing it with the int value.

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