Java was introduced as a "simple" programming language and consequently one would expect a simple performance model. The opposite is the truth. Complex and ambitious optimization techniques applied in the compiler and the runtime system improve an application's performance, but render an intuitive understanding of performance issues in Java close to impossible. Accordingly difficult is the development of high-performance Java software. In cases where the automatically applied optimizations do not suffice, the developer must cope with the complex Java performance model. 

In this tutorial we explain the Java performance model and illustrate its complexities, using examples from our industrial experience. In this context we discuss strategies for detection and evaluation of information related to the performance model and the use of tools that support detection of performance impediments.