java - 处理短数据类型的变量

Question

我有一个方法，其中我收到的参数是“rowno”，其类型为短。代码如下所示。

private int abcd (int a , short rownum)
{
    // method body
}

现在我的查询是这样的。在方法内部，当以下值时，我必须执行一些逻辑rownum 是 5 ，所以我尝试这样

if (rowno == 5)
{
     //perform some operation

}

请告诉我这是否是短类型的正确方法。

Answer 1

这应该可以正常工作。

当 rowno 为 short 时，表达式 rowno == 5 相当于 ((int) rowno) == 5 因为 Java 隐式提升了原始操作数。

Java Language Specification说

5.6.2. Binary Numeric Promotion

When an operator applies binary numeric promotion to a pair of operands, each of which must denote a value that is convertible to a numeric type, the following rules apply, in order:

2 Widening primitive conversion (§5.1.2) is applied to convert either or both operands as specified by the following rules:

• If either operand is of type double, the other is converted to double.
• Otherwise, if either operand is of type float, the other is converted to float.
• Otherwise, if either operand is of type long, the other is converted to long.
• Otherwise, both operands are converted to type int.

Binary numeric promotion is performed on the operands of certain operators:

...

• The numerical equality operators == and !=

根据

，此处发生的转换是安全的

5.1.2. Widening Primitive Conversion

19 specific conversions on primitive types are called the widening primitive conversions:

• ...
• short to int, long, float, or double
• ...

A widening primitive conversion from an integral type to another integral type, or from float to double in a strictfp expression (§15.4), does not lose any information at all; the numeric value is preserved exactly.