Chapter18

Chapter 18: Using Java with Other Languages

18.1 Running an External Program from Java

Problem

You want to run an external program from within a Java program.

Solution

Use one of the exec() methods in the java.lang.Runtime class. Or set up a ProcessBuilder and call its start() method.

18.2 Running a Program and Capturing Its Output

Problem

You want to run a program but also capture its output.

Solution

Use the Process object’s getInputStream() read and copy the contents to System.out or wherever you want them.

18.3 Calling Other Languages via javax.script

Problem

You want to invoke a script written in some other language from within your Java program, running in the JVM, with the ability to pass variables directly to/from the other language.

Solution

If the script you want is written in any of the two-dozen-plus supported languages, use javax.script. Those languages include awk, Perl, Python, Ruby, BeanShell, PNuts, Ksh/Bash, R (Renjin), and several implementations of JavaScript.

18.7 Calling Other Languages via Native Code or Calling Java from Native Code

Problem

You wish to call native C/C++ functions from Java or the other way around: you need to call Java from C/C++ code.

Solution

Use JNI (Java Native Interface).