[Java性能优化指南]Java Performance: The Definitive Guide

中文名：Java性能优化指南 此书对提高编写java程序有很好的参考作用，不过是英文版的，对着词典看也能看完。 Who Should (and Shouldn’t) Read This Book This book is designed for performance engineers and developers who are looking to understand how various aspects of the JVM and the Java APIs impact performance. If it is late Sunday night, your site is going live Monday morning, and you’re looking for a quick fix for performance issues, this is not the book for you. x | PrefaceIf you are new to performance analysis and are starting that analysis in Java, then this book ca n help you. Certainly my goal is to provide enough information and context that novice engineers can understand how to apply basic tuning and performance prin‐ ciples to a Java application. However, system analysis is a very broad field. There are a number of excellent resources for system analysis in general (and those pricincples of course apply to Java), and in that sense, this book will hopefully be a useful companion to those texts. At a fundamental level, though, making Java go really fast requires a deep understanding about how the JVM (and Java APIs) actually work. There are literally hundreds of Java tuning flags, and tuning the JVM has to be more than an approach of blindly trying them and seeing what works. Instead, my goal is to provide some very detailed knowl‐ edge about what the JVM and APIs are doing, with the hope that if you understand how those things work, you’ll be able to look at the specific behavior of an application and understand why it is performing badly. Understanding that, it becomes a simple (or at least simpler) task to get rid of undesirable (badly performing) behavior. One interesting aspect to Java performance work is that developers often have a very different background than engineers in a performance or QA group. I know developers who can remember thousands of obscure method signatures on little-used Java APIs but who have no idea what the flag -Xmn means. And I know testing engineers who can get every last ounce of performance from setting various flags for the garbage collector but who could barely write a suitable “Hello, World” program in Java. Java performance covers both of these areas: tuning flags for the compiler and garbage collector and so on, and best-practice uses of the APIs. So I assume that you have a good understanding of how to write programs in Java. Even if your primary interest is not in the programming aspects of Java, I do spent a fair amount of time discussing programs, including the sample programs used to provide a lot of the data points in the examples. Still, if your primary interest is in the performance of the JVM itself—meaning how to alter the behavior of the JVM without any coding—then large sections of this book should still be beneficial to you. Feel free to skip over the coding parts and focus in on the areas that interest you. And maybe along the way, you’ll pick up some insight into how Java applications can affect JVM performance and start to suggest changes to de‐ velopers so they can make your performance-testing life easier. n help you. Certainly my goal is to provide enough information and context that novice engineers can understand how to apply basic tuning and performance prin‐ ciples to a Java application. However, system analysis is a very broad field. There are a number of excellent resources for system analysis in general (and those pricincples of course apply to Java), and in that sense, this book will hopefully be a useful companion to those texts. At a fundamental level, though, making Java go really fast requires a deep understanding about how the JVM (and Java APIs) actually work. There are literally hundreds of Java tuning flags, and tuning the JVM has to be more than an approach of blindly trying them and seeing what works. Instead, my goal is to provide some very detailed knowl‐ edge about what the JVM and APIs are doing, with the hope that if you understand how those things work, you’ll be able to look at the specific behavior of an application and understand why it is performing badly. Understanding that, it becomes a simple (or at least simpler) task to get rid of undesirable (badly performing) behavior. One interesting aspect to Java performance work is that developers often have a very different background than engineers in a performance or QA group. I know developers who can remember thousands of obscure method signatures on little-used Java APIs but who have no idea what the flag -Xmn means. And I know testing engineers who can get every last ounce of performance from setting various flags for the garbage collector but who could barely write a suitable “Hello, World” program in Java. Java performance covers both of these areas: tuning flags for the compiler and garbage collector and so on, and best-practice uses of the APIs. So I assume that you have a good understanding of how to write programs in Java. Even if your primary interest is not in the programming aspects of Java, I do spent a fair amount of time discussing programs, including the sample programs used to provide a lot of the data points in the examples. Still, if your primary interest is in the performance of the JVM itself—meaning how to alter the behavior of the JVM without any coding—then large sections of this book should still be beneficial to you. Feel free to skip over the coding parts and focus in on the areas that interest you. And maybe along the way, you’ll pick up some insight into how Java applications can affect JVM performance and start to suggest changes to de‐ velopers so they can make your performance-testing life easier.