这个压缩包里的都是超级经典的java例子

				
				
				
				Controlling Access to an Object (Java Developers Almanac Example)
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				
				The Java Developers Almanac 1.4
				
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				    java.security
				         [30 examples]
				    
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				        Permissions
				             [7 examples]
				            
				
				  e216. Controlling Access to an Object
				
				This example demonstrates how to protect access to an object 
				using a permission. Only threads with the required permission can
				access the object.
				
				
				    // Create the object that requires protection
				    String secretObj = "my secret";
				    
				    // Create the required permission that will protect the object
				    Guard guard = new PropertyPermission("java.home", "read");
				    
				    // Create the guard
				    GuardedObject gobj = new GuardedObject(secretObj, guard);
				    
				    // Get the guarded object
				    try {
				        Object o = gobj.getObject();
				    } catch (AccessControlException e) {
				        // Cannot access the object
				    }
				
				
				
				
				             Related Examples
				
				
				
				
				e212. 
				    Enabling the Security Manager
				
				
				
				e213. 
				    Checking Read/Write Permission for a Directory
				
				
				
				e214. 
				    Determining If One Permission Implies Another
				
				
				
				e215. 
				    Creating a Custom Permission
				
				
				
				e217. 
				    Listing All Permissions Granted to a Loaded Class
				
				
				
				e218. 
				    Listing All Permissions Granted to Classes Loaded from a URL or Directory
				
				
				
				
				
				
				
				
				        See also: 
				
				    Key Store
				  
				
				
				    Message Digests
				  
				
				
				    Policy Files
				  
				
				
				    Public and Private Keys
				  
				
				
				    Signatures
				  
				
				
				
				
				
				
				
				
				
				© 2002 Addison-Wesley.