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class SensitiveHash {
  Hashtable<Integer,String> ht = new Hashtable<Integer,String>();
  
  public void removeEntry(Object key) {
    ht.remove(key);
  }
}

class SensitiveHash {
  Hashtable<Integer,String> ht = new Hashtable<Integer,String>();

  void removeEntry(Object key) {
    check("removeKeyPermission");
    ht.remove(key);    
  }

  private void check(String directive) {
    SecurityManager sm = System.getSecurityManager();
      if (sm != null) {
        sm.checkSecurityAccess(directive);
      }
  }
}

SecurityManager sm = System.getSecurityManager();

if(sm != null) {  //check if file can be read
  sm.checkRead("/local/schema.dtd");
} 

SecurityManager sm = System.getSecurityManager();
  
if(sm != null) {  //check if file can be read
  DTDPermission perm = new DTDPermission("/local/",  "readDTD");
  sm.checkPermission(perm);
}

// Take the snapshot of the required context, store in acc and pass it to another context
AccessControlContext acc = AccessController.getContext(); 

// Accept acc in another context and invoke checkPermission() on it
acc.checkPermission(perm);