ECJ is the European Court of Justice, the highest court in the European Union in matters of European Union law. ECJ may also refer to: Computing Java Evolutionary Computation Toolkit, a Java-based evolutionary Computation Research System Eclipse Compiler for Java, a Java compiler in the Eclipse framework Other uses Eclipse ECJ, a very light jet produced by Eclipse Aviation Escuela Complementaria Japonesa de Madrid, a Japanese international school in Madrid Evolutionary Computation Journal, a scientific journal on evolutionary computation See also Court of Justice of the European Union (CJEC), the full court system of the European Union