在java中为int包装类指定一个int文字 [英] Assigning an int literal to a long wrapper class in java

问题描述

为什么 Long l = 3 时出现编译错误而不是 Long l = 3L ？

Why is there a compilation error with Long l = 3 and not with Long l = 3L?

原始数据类型 long 同时接受 3 和3升。我知道 3 是一个 int 文字 - 但不能分配给长包装器对象？ int 只有32位不适合64位整数类型吗？

The primitive data type long accepts both 3 and 3l. I understand that 3 is an int literal - but it can't be assigned to a Long wrapper object? int is only 32 bits shouldn't it fit in a 64 bit integer type?

推荐答案

因为没有 int 到长加宽和自动装箱转换，自动装箱从长转换为长（但首先该值必须加宽 int 到 long ）。你可以做 3L ，或者

Because there isn't an int to Long widening and autoboxing conversion, autoboxing converts from long to Long (but first the value must be widened from an int to a long). You could do 3L as you have, or

Long l = Long.valueOf(3);

或

Long l = (long) 3;

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