Example: Calling another Java program with java.lang.Runtime.exec()

This example shows how to call another Java™ program with java.lang.Runtime.exec(). This class calls the Hello program that is shipped as part of the IBM Developer Kit for Java. When the Hello class writes to System.out, this program gets a handle to the stream and can read from it.

Source code for CallHelloPgm Java class

Note: By using the code examples, you agree to the terms of the Code license and disclaimer information.

import java.io.*;
 
public class CallHelloPgm
{
   public static void main(String args[])
   {
      Process theProcess = null;
      BufferedReader inStream = null;
 
      System.out.println("CallHelloPgm.main() invoked");
 
      // call the Hello class
      try
      {
          theProcess = Runtime.getRuntime().exec("java QIBMHello");
      }
      catch(IOException e)
      {
         System.err.println("Error on exec() method");
         e.printStackTrace();  
      }
        
      // read from the called program's standard output stream
      try
      {
         inStream = new BufferedReader(
                                new InputStreamReader( theProcess.getInputStream() ));  
         System.out.println(inStream.readLine());
      }
      catch(IOException e)
      {
         System.err.println("Error on inStream.readLine()");
         e.printStackTrace();  
      }
   } 
}