The Java Class Library represents external processes using the java.lang.Process class. Processes can be spawned using a java.lang.ProcessBuilder:

Process process = new ProcessBuilder("processname").start();

or the older interface exposed by the overloaded exec methods on the java.lang.Runtime class:

Process process = Runtime.getRuntime().exec("processname");

Both of these will code snippets will spawn a new process, which usually executes asynchronously and can be interacted with through the resulting Process object. If you need to check that the process has finished (or wait for it to finish), don't forget to check that the exit value (exit code) returned by process.exitValue() or process.waitFor() is as expected (0 for most programs), since no exception is thrown if the process exits abnormally.

Also note that additional code is often necessary to handle the process's I/O correctly, as described in the documentation for the Process class (emphasis added):

By default, the created subprocess does not have its own terminal or console. All its standard I/O (i.e. stdin, stdout, stderr) operations will be redirected to the parent process, where they can be accessed via the streams obtained using the methods getOutputStream(), getInputStream(), and getErrorStream(). The parent process uses these streams to feed input to and get output from the subprocess. Because some native platforms only provide limited buffer size for standard input and output streams, failure to promptly write the input stream or read the output stream of the subprocess may cause the subprocess to block, or even deadlock.

One way to make sure that I/O is correctly handled and that the exit value indicates success is to use a library like jproc that deals with the intricacies of capturing stdout and stderr, and offers a simple synchronous interface to run external processes:

ProcResult result = new ProcBuilder("processname").run();

jproc is available via maven central:

<dependency>
      <groupId>org.buildobjects</groupId>
      <artifactId>jproc</artifactId>
      <version>2.5.1</version>
</dependency>