“Hotspot 可以删除 Java 中的边界检查。”任何人都可以解释一下吗？实际上，我正在分析 C++ 和 Java 之间的差异。这不是家庭作业，我是根据自己的兴趣分析的。
最佳答案
谷歌搜索“热点边界检查”后，a Paper with the Title "Array Bounds Check Elimination for the Java HotSpot™ Client Compiler"出现(作为第一个结果)并给了我们一些见解:
摘要:
Whenever an array element is accessed, Java virtual machines execute a compare instruction to ensure that the index value is within the valid bounds. This reduces the execution speed of Java programs. Array bounds check elimination identifies situations in which such checks are redundant and can be removed. We present an array bounds check elimination algorithm for the Java HotSpot™ VM based on static analysis in the just-in-time compiler.
The algorithm works on an intermediate representation in static single assignment form and maintains conditions for index expressions. It fully removes bounds checks if it can be proven that they never fail. Whenever possible, it moves bounds checks out of loops. The static number of checks remains the same, but a check inside a loop is likely to be executed more often. If such a check fails, the executing program falls back to interpreted mode, avoiding the problem that an exception is thrown at the wrong place.
The evaluation shows a speedup near to the theoretical maximum for the scientific SciMark benchmark suite (40% on average). The algorithm also improves the execution speed for the SPECjvm98 benchmark suite (2% on average, 12% maximum).
Mark Mayo 很好地解释了这一点。
底线:如果 Hotspot 检测到不需要检查数组的边界，它会将此视为禁用该数组边界检查的机会，从而提高性能。
关于java - Java 中的边界检查，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/4469483/