java - 在Java中，这个 "double cannot be dereferenced"错误是什么意思？

Question

我有以下代码:

public class RandomCompliment {

  static final String[] comps  = { "gorgeous butterfly!", "strawberry milkshake!", "calm waterfall", "smart cookie", "big genius", "friendly cat" };

  public static void main(String[] args) {

    for (int i = 0; i < 200 ; i++ ) {
      System.out.print("Good monring, " + comps[(((20) * Math.sin(i)).intValue()) % comps.length]);
    }
  }
}

它给了我这个错误:

C:\Misc_Stuff\RandomScratch>javac RandomCompliment.java RandomCompliment.java:14: double cannot be dereferenced System.out.print(" " + comps[ ( ((20) * Math. sin(i)).intValue() ) % comps.length ]);

   ^ 1 error

这里的“取消引用”是什么意思？

Answer 1

Math.sin(i) 返回 double。您无法在 double(或任何原始数据类型)上调用方法 (intValue())。相反，您可以将 double 向下转换为 int:

(int) (20 * Math.sin(i))