JEPO

Java Energy Profiler & Optimizer is an eclipse plugin that provides method energy profiling and energy-saving suggestions for Java language. It can generate energy profile of methods by leveraging Javassist library to insert energy measurement code at the start and end of each method. Software developers can use it to either get real-time suggestions while typing the code or get energy-saving suggestions for a selected project. Energy profiling functionality is supported only on Linux. Energy optimization suggestions functionality is supported on all OS.

Installation

• Allow modprobe and rdmsr commands run without sudo, like this
• Move the jar file located in plugin folder above to eclipse dropin folder
• Restart the eclipse

How to use?

• Real-time energy-saving suggestions
  • Click icon located in Eclipse tool-bar menu
• Energy-saving suggestions for a project
  • Right-click on a project
  • Select JEPO -> Run Optimizer option
• Energy profiling of methods in a project
  • Add all libraries in lib folder above to project build path
  • Right-click on the project
  • Select JEPO -> Run Profiler option

Suggestions

Java Component	Suggestion
Variables	int is the most efficient primitive data type. Static variables consume up to 17,700% more energy compared to local variables. Access modifiers have no impact on a variable energy consumption. Scientific notation results in lower energy consumption of decimal numbers.
Operators	Modulus arithmetic operator consumes up to 1,620% more energy than other arithmetic operators. Putting most common cases first in short circuit operators can save up to 87% energy. Normal and compound assignments have the same amount of energy consumption. Post-increment, pre-increment , post- decrement and pre-decrement operators consume same energy.
Control Statements	Ternary operator consume up to 37% more energy than if-then-else statement. int is the most energy efficient iteration variable in a for loop. for, while and do-while loop statements consume same energy. Enhanced for statement consumes the same energy as the for statement. Method termination expression can consume higher energy than the variable termination expression.
Exception	Try-catch block scope can change how it consume energy. Executing a catch block results in higher energy consumption.
String	StringBuilder append method consumes up to 1,48,069% lower energy than String concatenation operator. Integer toString, and String valueOf consume same energy. String compareTo method consumes up to 33% more energy than String equals method.
Object	Wrapper classes object are more energy expensive as compared to primitive data types. Double wrapper class object consume up to 115% more energy than Integer wrapper class object.
Thread	Creating Threads by implementing a Runnable interface or extending Thread class consume same energy.
Arrays	System.arraycopy() is the most energy efficient way to copy Arrays. Two-dimensional Array column traversal result in up to 793% more energy.