铸造的乘法两个正整数结果长是负值 [英] Casting result of multiplication two positive integers to long is negative value

问题描述

我有code是这样的：

  INT A = 629339;
INT B = 4096;
长解析度= A * B;
 

结果是 -1717194752 但如果我加一个手动施放长长RES =（（长）一）* B; 或长RES =（长）A * B ; 的结果是正确的 2577772544 谁可以解释它是如何工作的。

解决方案

 长解析度= A * B;
 

A * B 除非你在末尾加上L将被视为整数（或）铸造。

根据 Java教程

  

int数据类型是一个32位有符号二进制补码整数。它有2,147,483,648最小值和2147483647的最大值（含）。对于整数值，此数据类型通常是默认选项，除非是有原因（如上述）选择别的东西。

I have code like this :

int a = 629339;
int b = 4096;
long res = a*b;

The result is -1717194752 but if I add one manual cast to long long res = ((long)a)*b; or long res = (long) a*b; the result is correct 2577772544 Who can explain how does it works.

解决方案

long res = a*b;

a*b will be treated as integer unless you add 'l' at end (or) cast.

As per java tutorial

The int data type is a 32-bit signed two's complement integer. It has a minimum value of -2,147,483,648 and a maximum value of 2,147,483,647 (inclusive). For integral values, this data type is generally the default choice unless there is a reason (like the above) to choose something else.

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