Java.lang.Runtime.exec() Method



The java.lang.Runtime.exec(String[] cmdarray) method executes the specified command and arguments in a separate process. This is a convenience method. An invocation of the form exec(cmdarray) behaves in exactly the same way as the invocation exec(cmdarray, null, null).


Following is the declaration for java.lang.Runtime.exec() method

public Process exec(String[] cmdarray)


  • cmdarray -- array containing the command to call and its arguments.

Return Value

This method returns a new Process object for managing the subprocess


  • SecurityException -- If a security manager exists and its checkExec method doesn't allow creation of the subprocess

  • IOException -- If an I/O error occurs

  • NullPointerException -- If command is null

  • IndexOutOfBoundsException -- If cmdarray is an empty array (has length 0)


This example requires a file named example.txt in our CLASSPATH with the following contents:

Hello World!

The following example shows the usage of lang.Runtime.exec() method.

package com.tutorialspoint;

public class RuntimeDemo {

   public static void main(String[] args) {
   try {

   // create a new array of 2 strings
   String[] cmdArray = new String[2];

   // first argument is the program we want to open
   cmdArray[0] = "notepad.exe";

   // second argument is a txt file we want to open with notepad
   cmdArray[1] = "example.txt";

   // print a message
   System.out.println("Executing notepad.exe and opening example.txt");

   // create a process and execute cmdArray
   Process process = Runtime.getRuntime().exec(cmdArray);

   // print another message
   System.out.println("example.txt should now open.");

   } catch (Exception ex) {


Let us compile and run the above program, this will produce the following result:

Executing notepad.exe and opening example.txt
example.txt should now open.