When developing in Python or Perl, it is very common to start with an executable script, and to edit/run/edit/run.  Java is slowed down by the cycle of edit/compile/run.  Here’s a proof of concept of coding in Java like you do in Python.

First, the code to compile and run the script. This is unrefactored, and uses the system command, which is basically a new shell, so not what the end product should look like:

#include 
#include 
#include 
#include 


void execute(const char * file_name){
  char * execute_command = "java ";
  int command_size = + strlen( execute_command ) +  strlen(file_name) + 1 ;
  char * command = malloc(command_size);
  sprintf(command,"%s %s", execute_command , file_name);
  system(command);
  free(command);
}
void compile(const char * file_name){
  char * compile_command = "javac ";
  int command_size = + strlen( compile_command ) +  strlen(file_name) + 1 ;
  char * command = malloc(command_size);
  sprintf(command,"%s %s", compile_command , file_name);
  system(command);
  free(command);
}
char *  make_java_file_name(const char * source){
  int command_size = strlen(source) + strlen(".java") + 1 ;
  char * command = malloc(command_size);
  sprintf(command,"%s.java", source);
  return command;
}
void copy_file(const char * source, const char * dest ){
  char * cp_command = "tail -n +2 ";
  int command_size =
    strlen( cp_command ) + 2 +
    strlen(source) + 1 +
    strlen(dest) + 1 ;
  char * command = malloc(command_size);
  sprintf(command,"%s %s > %s", cp_command , source, dest);
  system(command);
  free(command);
}

int main(int argc,  char ** argv){
  printf("Got argc=%d\n",argc);
  int i;
  for (i =0; i < argc; i ++){
    printf("[%d]:%s\n",i,argv[i]);
  }

  if (argc < 2){
    return;
  }

  char * file_name = basename (argv[1]);
  char * java_file_name = make_java_file_name(file_name);

  copy_file(file_name, java_file_name);
  compile(java_file_name);
  free(java_file_name);
  execute(file_name);
}

I save that in a file called javaexec.c and compile it.

Now to call it. The following file is named simply runexec

#!/home/ayoung/devel/javahacks/javaexec/javaexe
public class runexec{

       public static void main(String[] args){
              System.out.println("Running on Empty!");
       }
}

chmod it and execute:

[ayoung@ayoung javaexec]$ ./runexec
Got argc=2
[0]:/home/ayoung/devel/javahacks/javaexec/javaexec
[1]:./runexec
Running on Empty!

OK. It works in the simple case. Things to do: path handling, classpath, argument passing, cleanup the C code and maybe get rid of all those "systems".