We’ve made the jump from interpretation to actual compiling of expressions. To start your code-generating compiler, download the BCEL library from http://jakarta.apache.org/bcel/.
Add the library to your project build path and write an example Java program as shown in the lecture. Run the BCELifier tool that comes with the library and take a good look at the output. Refer to the BCEL manual to get a better understanding of the code. Now, modify your interpreter to initialize the bytecode generation facilities. Remove the call to your recursive interpreter. This will cause your tests to fail, so delete or ignore them for now. Write a simple test which evaluates a string which only contains a number. Include the code produced by BCELifier in your parser method. You can leave the hardcoded numerical value in the code. Check that a .class file is generated and load it using the Java ClassLoader, invoke the generated method using java.lang.reflect, and return the result produced by the generated code.
We will start to generate code from the input text in the next homework.