java - 移位运算符 - 操作数必须可转换为整数基元？

Question

我正在准备参加 Java 考试，并且正在阅读“OCA Java SE 8 程序员学习指南(考试 1Z0-808)”。在运营商部分，我发现了这句话:

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

我觉得很奇怪，所以我用 long 测试了它:

public class HelloWorld{

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

     }
}

它成功了，没有编译器错误，结果是正确的。这本书有错误还是我误解了书中的引述？

Answer 1

移位运算符 >>和 <<在 JLS section 15.19 中定义.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“原始整数”时，这本书实际上是在谈论“原始整数类型”(在 JLS section 4.2.1 中定义):

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