jvm-hotspot

When I reading the book of "Scala in depth", it mentions that HotSpot compiler has several important features, one of them is "Dynamic De-Optimization": It is the ability to determine if an optimization did not , in fact, improve performance and undo that optimization,allowing others to be applied It seems HotSpot will try all kinds of "optimization"s, and choose the best one of them. But I'm not quite understand it. Is the "optimization" here all provided by HotSpot? I mean programmers often try to optimize the code with some skills, will HotSpot handle them? And is there any common

Pure methods are those without side effects: their only effect is to return a value which is a function of their arguments. Two calls to the same pure method with the same arguments will return the same value. So, given two calls to a pure method with identical arguments, can HotSpot optimize away the second call, simply re-using the value from the first call? For example: int add(int x, int y) { return x + y; } int addTwice(int x, int y) { return add(x, y) + add(x, y); } If HotSpot doesn't inline add inside addTwice does it understand that add is pure and thus call add only once and double

I am asking a question about "java stack overflow" in the "stackoverflow" site :) A particular thread which makes some recursive function calls for a particular input runs fine in Oracle Java 7 (64 bit) for a configured stack size of 228k (-Xss228k). However, the same thread running the same recursive code for the same input throws a java.lang.StackOverflowError in Oracle Java 8 (64 bit) for the same stack size of 228k. It runs fine in Java 8 if the stack size is increased to 512k (-Xss512k). Any idea why this could happen? Have any changes been made in Java 8 (Hotspot JVM) compared to Java 7

The consensus seems to be that there is a performance benefit to marking member variables as final because they never need reloading from main memory. My question is, do javac or Hotspot automatically do this for me when it's obvious the variable cannot change. eg will javac make 'x' final in this class below... public class MyClass { private String x; MyClass(String x) { this.x = x; } public String getX() { return x; } } On a secondary point, has anyone produced empirical evidence that marking members as final makes code run faster? Any benefit is surely negligible in any application making

I am upgrading my application from java 1.6 to 1.7. When I try to build using Maven 3.2.1, my build fails with below error msg: [ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:2.0.2:compile (default-compile) on project my-app5: Compilation failure: Compilation failure: [ERROR] could not parse error message: warning: [options] bootstrap class path not set in conjunction with -source 1.6 I am using java 1.7 hotspot and previously I was using 1.6 jrockit. My application is multi module and few modules compile and build as usual, this module failed. I have set java