java – Shift操作符 – 操作数必须可以转换为整数原语？

发布时间：2020-12-14 05:22:43 所属栏目：Java 来源：网络整理

导读：我正在准备 Java考试,我正在阅读“OCA Java SE 8程序员学习指南(考试1Z0-808)”.在运算符部分我发现这句话： Shift Operators: A shift operator takes two operands whose type must be convertible to an integer primitive. 我对我感到奇怪,所以我测试了

我正在准备 Java考试,我正在阅读“OCA Java SE 8程序员学习指南(考试1Z0-808)”.在运算符部分我发现这句话：

Shift Operators: A shift operator takes two operands whose type must be
convertible to an integer primitive.

我对我感到奇怪,所以我测试了很长时间：

public class HelloWorld{

     public static void main(String []args){
         long test = 3147483647L;
         System.out.println(test << 1);

     }
}

它的工作,没有编译器错误和结果是正确的.这本书是否有错误或我误会书中的引用？

解决方法

移位运算符>>和<定义在 JLS section 15.19.引用：

Unary numeric promotion (§5.6.1) is performed on each operand separately. (Binary numeric promotion (§5.6.2) is not performed on the operands.)

It is a compile-time error if the type of each of the operands of a shift operator,after unary numeric promotion,is not a primitive integral type.

当谈到“整数原始”时,这本书真的在谈论“原始积分类型”(定义在JLS section 4.2.1)：

The values of the integral types are integers in the following ranges:

For byte,from -128 to 127,inclusive

For short,from -32768 to 32767,inclusive

For int,from -2147483648 to 2147483647,inclusive

For long,from -9223372036854775808 to 9223372036854775807,inclusive

For char,from ‘u0000’ to ‘uffff’ inclusive,that is,from 0 to 65535

（编辑：李大同）

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