Launching without compiling, a main interface... a Mark Reinhold story
During jdk 1.1 development, there was obviously no consensus on test suites (i.e., JUnit), and the JavaSoft JCK tests required a ridiculous amount of html documentation for tracing to specs. Mark Reinhold, the jdk tech lead, refused to have his team write tests in JCK form, so instead he wrote a small harness with a compiling class loader: point the harness at a directory tree of .java files, and it would run them all, compiling as needed. The test interface was just a main function, and if it threw an exception, it failed. Pure and simple.
But probably the best magic trick for Java programmers is debugger hot reload. You write some empty methods, start the debugger, and then code iteratively, reloading as needed. (Set up the data and interfaces right, and change method bodies as you wish.) It's so much easier than recompile-println when you're just getting started, and after you've grown up and out, it's easier than rebuild/redeploy when you're working on a big system.
During jdk 1.1 development, there was obviously no consensus on test suites (i.e., JUnit), and the JavaSoft JCK tests required a ridiculous amount of html documentation for tracing to specs. Mark Reinhold, the jdk tech lead, refused to have his team write tests in JCK form, so instead he wrote a small harness with a compiling class loader: point the harness at a directory tree of .java files, and it would run them all, compiling as needed. The test interface was just a main function, and if it threw an exception, it failed. Pure and simple.
But probably the best magic trick for Java programmers is debugger hot reload. You write some empty methods, start the debugger, and then code iteratively, reloading as needed. (Set up the data and interfaces right, and change method bodies as you wish.) It's so much easier than recompile-println when you're just getting started, and after you've grown up and out, it's easier than rebuild/redeploy when you're working on a big system.