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Chapter 1. Introduction

JVM Tuning Flags

Boolean flags use this syntax: -XX:+FlagName enables the flag, and -XX:-FlagName disables the flag. Flags that require a parameter use this syntax: -XX:FlagName=something. -XX:PrintFlagsFinal determines the default value for a particular flag in a particular environment.

The Complete Performance Story

  • Write Better Algorithms

  • Write Less Code

  • Oh Go Ahead, Prematurely Optimize

    Avoid code constructs that are known to be bad for performance

    log.log(Level.FINE, "I am here, and the value of X is "
        + calcX() + " and Y is " + calcY());

// better
if (log.isLoggable(Level.FINE)) {
    log.log(Level.FINE,
            "I am here, and the value of X is {} and Y is {}",
            new Object[]{calcX(), calcY()});
}

  • Look Elsewhere: The Database is Always the Bottleneck

  • Optimize for the Common Case