问题

var foo = (short) 40 + (byte) 10;

foo占用多少字节？
它的类型是什么？

我预期结果会存储在short中，但为了节省内存，JVM会测试以查看是否适合更小的原始类型吗？

如果是(short) 1 + (byte) 1，它仍然是short吗？

英文:

var foo = (short) 40 + (byte) 10

How many bytes does foo take up?
What is its type?

I would expect that the result is stored in a short, but to save memory does the JVM test to see if it will fit in a smaller primitive?

If it were (short) 1 + (byte) 1 would it still be a short?

答案1

得分: 4

经验法则：如果其中一个参数是long，整数算术运算会被视为long，并且结果也是long，否则为int。

我还怀疑JVM即使在存储byte、short（以及boolean）变量时也会使用4字节 - 请参阅JVMS 2.6.1. 本地变量和表2.11.1-B。

甚至
var test = (byte)1 + (byte)1
都会导致test是一个int。

但对于var test = (byte)(1 + 1)，情况不同。

英文:

Rule of thumb: integer arithmetic operations are done as long and result in long if either argument is long, int otherwise.

I also suspect that the JVM uses 4 bytes even to store byte and short (and boolean) variables - see JVMS 2.6.1. Local Variables and Table 2.11.1-B.

Even
var test = (byte)1 + (byte)1
will cause test to be an int.

Not the case for var test = (byte)(1 + 1)

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