Java.lang.SecurityManager.checkRead() Method


The java.lang.SecurityManager.checkRead(FileDescriptor fd) method throws a SecurityException if the calling thread is not allowed to read from the specified file descriptor. This method calls checkPermission with the RuntimePermission("readFileDescriptor") permission.If you override this method, then you should make a call to super.checkRead at the point the overridden method would normally throw an exception.


Following is the declaration for java.lang.SecurityManager.checkRead() method

public void checkRead(FileDescriptor fd)


fd − the system-dependent file descriptor.

Return Value

This method does not return a value.


  • SecurityException − if the calling thread does not have permission to access the specified file descriptor.

  • NullPointerException − if the file descriptor argument is null.


Our examples require that the permissions for each command is blocked. A new policy file was set that allows only the creating and setting of our Security Manager. The file is in C:/java.policy and contains the following text −

grant {
   permission java.lang.RuntimePermission "setSecurityManager";
   permission java.lang.RuntimePermission "createSecurityManager";
   permission java.lang.RuntimePermission "usePolicy";

The following example shows the usage of lang.SecurityManager.checkRead() method.

package com.tutorialspoint;


public class SecurityManagerDemo extends SecurityManager {

   public static void main(String[] args) {

      // set the policy file as the system securuty policy
      System.setProperty("", "file:/C:/java.policy");

      // create a security manager
      SecurityManagerDemo sm = new SecurityManagerDemo();

      // set the system security manager

      // perform the check
      FileDescriptor fd = new FileDescriptor();

      // print a message if we passed the check

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

Exception in thread "main" access denied (java.lang.RuntimePermission readFileDescriptor)