Java Cookbook, 2nd Edition

Chapter 26. Using Java with Other Languages

Introduction

Java has several methods of running programs written in other languages. You can invoke a compiled program or executable script using Runtime.exec( ) , as I’ll describe in Recipe 26.1. Or you can drop down to C level with Java’s "native code” mechanism and call compiled functions written in C/C++. From there, you can call to functions written in just about any language. Not to mention that you can contact programs written in any language over a socket (see Chapter 17), with HTTP services (see Chapter 18), or with Java clients in RMI or CORBA clients in a variety of languages (see Chapter 22).

There is an element of system dependency here, of course. You can only run Windows applications under Windows and Unix applications under Unix. So some of the recipes in this chapter aren’t portable, although in a few cases I try to make them at least run on Windows or Unix.

26.1. Running a Program

Problem

You want to run a program.

Solution

Use one of the exec( ) methods in the java.lang.Runtime class. Or, on JDK 1.5, use the start( ) method of ProcessBuilder.

Discussion

The exec( ) method in the Runtime class lets you run an external program. The command line you give is broken into strings by a simple StringTokenizer (Recipe 3.2) and passed on to the operating system’s “execute a program” system call. As an example, here is a simple program that uses exec( ) to run kwrite , a windowed text editor program.^[1] On Windows, you’d have to ...