为什么在outOfBoundsMsg中有私有方法java.util.ArrayList？

Question

这是来自java.util.ArrayList的片段

/**
 * Constructs an IndexOutOfBoundsException detail message.
 * Of the many possible refactorings of the error handling code,
 * this "outlining" performs best with both server and client VMs.
 */
private String outOfBoundsMsg(int index) {
    return "Index: "+index+", Size: "+size;
}

这是来自com.google.collect.Preconditions的片段

  /*
   * All recent hotspots (as of 2009) *really* like to have the natural code
   *
   * if (guardExpression) {
   *    throw new BadException(messageExpression);
   * }
   *
   * refactored so that messageExpression is moved to a separate
   * String-returning method.
   *
   * if (guardExpression) {
   *    throw new BadException(badMsg(...));
   * }
   *
   * The alternative natural refactorings into void or Exception-returning
   * methods are much slower.  This is a big deal - we're talking factors of
   * 2-8 in microbenchmarks, not just 10-20%.  (This is a hotspot optimizer
   * bug, which should be fixed, but that's a separate, big project).
   *
   * The coding pattern above is heavily used in java.util, e.g. in ArrayList.
   * There is a RangeCheckMicroBenchmark in the JDK that was used to test this.

希望有人能阐明：

• 为什么需要私有outOfBoundsMsg
• 意思是“这个大纲表现最好.”
• 是否应该开始重构代码以包含异常构造函数的字符串返回方法？

Answer 1

意思是“这个大纲表现最好.”

这是相反的内联，但不是一个标准的术语，这就是为什么它是常见的。

为什么需要私有outOfBoundsMsg

这就是“大纲”的意思--将代码提取到单独的方法中。

是否应该开始重构代码以包含异常构造函数的字符串返回方法？

如果您关心每次抛出没有字符串文字的异常时浪费3纳秒时间，那么是的。换句话说:没有。