Java Runtime exec() Method

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Description

The Java Runtime exec(String command, String[] envp) method executes the specified string command in a separate process with the specified environment. This is a convenience method. An invocation of the form exec(command, envp) behaves in exactly the same way as the invocation exec(command, envp, null).

Declaration

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

public Process exec(String command, String[] envp)

Parameters

• command − a specified system command.

• envp − array of strings, each element of which has environment variable settings in the format name=value, or null if the subprocess should inherit the environment of the current process.

Return Value

This method returns a new Process object for managing the subprocess

Exception

• 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, or one of the elements of envp is null

• IllegalArgumentException − If command is empty

Example: Opening a Notepad Application

The following example shows the usage of Java Runtime exec() method. We've created a Process object for notepad executable using exec() method. This will invoke the notepad application. If some exception occurs, a corresponding stack trace is printed with error message.

package com.tutorialspoint;

import java.io.File;

public class RuntimeDemo {

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

         // print a message
         System.out.println("Executing notepad.exe...");

         // create a process and execute notepad.exe and currect environment
         Process process = Runtime.getRuntime().exec("notepad.exe", null);

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

      } catch (Exception ex) {
         ex.printStackTrace();
      }
   }
}

Output

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

Executing notepad.exe...
Notepad should now open.

Example: Opening a Calculator Application

The following example shows the usage of Java Runtime exec() method. We've created a Process object for calc executable using exec() method. This will invoke the calculator application. If some exception occurs, a corresponding stack trace is printed with error message.

package com.tutorialspoint;

public class RuntimeDemo {

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

         // print a message
         System.out.println("Executing calc.exe...");

         // create a process and execute calc.exe and currect environment
         Process process = Runtime.getRuntime().exec("calc.exe", null);

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

      } catch (Exception ex) {
         ex.printStackTrace();
      }
   }
}

Output

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

Executing calc.exe...
Calculator should now open.

Example: Opening a Windows Explorer Application

The following example shows the usage of Java Runtime exec() method. We've created a Process object for Windows Explorer executable using exec() method. This will invoke the Windows Explorer application. If some exception occurs, a corresponding stack trace is printed with error message.

package com.tutorialspoint;

public class RuntimeDemo {

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

         // print a message
         System.out.println("Executing explorer.exe...");

         // create a process and execute calc.exe and currect environment
         Process process = Runtime.getRuntime().exec("explorer.exe", null);

         // print another message
         System.out.println("Windows Explorer should now open.");

      } catch (Exception ex) {
         ex.printStackTrace();
      }
   }
}

Output

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

Executing explorer.exe...
Windows Explorer should now open.