import java.io.InputStream;
import java.io.PrintStream;
+import java.util.AbstractCollection;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
import java.util.Properties;
import java.util.PropertyPermission;
public static final PrintStream err = VMSystem.makeStandardErrorStream();
/**
+ * A cached copy of the environment variable map.
+ */
+ private static Map<String,String> environmentMap;
+
+ /**
* This class is uninstantiable.
*/
private System()
SecurityManager sm = SecurityManager.current; // Be thread-safe.
if (sm != null)
sm.checkPermission(new RuntimePermission("setIO"));
+
VMSystem.setIn(in);
}
{
SecurityManager sm = SecurityManager.current; // Be thread-safe.
if (sm != null)
- sm.checkPermission(new RuntimePermission("setIO"));
-
+ sm.checkPermission(new RuntimePermission("setIO"));
VMSystem.setOut(out);
}
{
return VMSystem.currentTimeMillis();
}
-
+
/**
* <p>
* Returns the current value of a nanosecond-precise system timer.
}
/**
+ * <p>
+ * Returns an unmodifiable view of the system environment variables.
+ * If the underlying system does not support environment variables,
+ * an empty map is returned.
+ * </p>
+ * <p>
+ * The returned map is read-only and does not accept queries using
+ * null keys or values, or those of a type other than <code>String</code>.
+ * Attempts to modify the map will throw an
+ * <code>UnsupportedOperationException</code>, while attempts
+ * to pass in a null value will throw a
+ * <code>NullPointerException</code>. Types other than <code>String</code>
+ * throw a <code>ClassCastException</code>.
+ * </p>
+ * <p>
+ * As the returned map is generated using data from the underlying
+ * platform, it may not comply with the <code>equals()</code>
+ * and <code>hashCode()</code> contracts. It is also likely that
+ * the keys of this map will be case-sensitive.
+ * </p>
+ * <p>
+ * Use of this method may require a security check for the
+ * RuntimePermission "getenv.*".
+ * </p>
+ *
+ * @return a map of the system environment variables.
+ * @throws SecurityException if the checkPermission method of
+ * an installed security manager prevents access to
+ * the system environment variables.
+ * @since 1.5
+ */
+ public static Map<String, String> getenv()
+ {
+ SecurityManager sm = SecurityManager.current; // Be thread-safe.
+ if (sm != null)
+ sm.checkPermission(new RuntimePermission("getenv.*"));
+ if (environmentMap == null)
+ {
+ List<String> environ = (List<String>)VMSystem.environ();
+ Map<String,String> variables = new EnvironmentMap();
+ for (String pair : environ)
+ {
+ String[] parts = pair.split("=");
+ if (parts.length == 2)
+ variables.put(parts[0], parts[1]);
+ else
+ variables.put(parts[0], "");
+ }
+ environmentMap = Collections.unmodifiableMap(variables);
+ }
+ return environmentMap;
+ }
+
+ /**
* Terminate the Virtual Machine. This just calls
* <code>Runtime.getRuntime().exit(status)</code>, and never returns.
* Obviously, a security check is in order, <code>checkExit</code>.
return VMRuntime.mapLibraryName(libname);
}
+
+ /**
+ * This is a specialised <code>Collection</code>, providing
+ * the necessary provisions for the collections used by the
+ * environment variable map. Namely, it prevents
+ * querying anything but <code>String</code>s.
+ *
+ * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
+ */
+ private static class EnvironmentCollection
+ extends AbstractCollection<String>
+ {
+
+ /**
+ * The wrapped collection.
+ */
+ protected Collection<String> c;
+
+ /**
+ * Constructs a new environment collection, which
+ * wraps the elements of the supplied collection.
+ *
+ * @param coll the collection to use as a base for
+ * this collection.
+ */
+ public EnvironmentCollection(Collection<String> coll)
+ {
+ c = coll;
+ }
+
+ /**
+ * Blocks queries containing a null object or an object which
+ * isn't of type <code>String</code>. All other queries
+ * are forwarded to the underlying collection.
+ *
+ * @param obj the object to look for.
+ * @return true if the object exists in the collection.
+ * @throws NullPointerException if the specified object is null.
+ * @throws ClassCastException if the specified object is not a String.
+ */
+ public boolean contains(Object obj)
+ {
+ if (obj == null)
+ throw new
+ NullPointerException("This collection does not support " +
+ "null values.");
+ if (!(obj instanceof String))
+ throw new
+ ClassCastException("This collection only supports Strings.");
+ return c.contains(obj);
+ }
+
+ /**
+ * Blocks queries where the collection contains a null object or
+ * an object which isn't of type <code>String</code>. All other
+ * queries are forwarded to the underlying collection.
+ *
+ * @param coll the collection of objects to look for.
+ * @return true if the collection contains all elements in the collection.
+ * @throws NullPointerException if the collection is null.
+ * @throws NullPointerException if any collection entry is null.
+ * @throws ClassCastException if any collection entry is not a String.
+ */
+ public boolean containsAll(Collection<?> coll)
+ {
+ for (Object o: coll)
+ {
+ if (o == null)
+ throw new
+ NullPointerException("This collection does not support " +
+ "null values.");
+ if (!(o instanceof String))
+ throw new
+ ClassCastException("This collection only supports Strings.");
+ }
+ return c.containsAll(coll);
+ }
+
+ /**
+ * This returns an iterator over the map elements, with the
+ * same provisions as for the collection and underlying map.
+ *
+ * @return an iterator over the map elements.
+ */
+ public Iterator<String> iterator()
+ {
+ return c.iterator();
+ }
+
+ /**
+ * Blocks the removal of elements from the collection.
+ *
+ * @return true if the removal was sucessful.
+ * @throws NullPointerException if the collection is null.
+ * @throws NullPointerException if any collection entry is null.
+ * @throws ClassCastException if any collection entry is not a String.
+ */
+ public boolean remove(Object key)
+ {
+ if (key == null)
+ throw new
+ NullPointerException("This collection does not support " +
+ "null values.");
+ if (!(key instanceof String))
+ throw new
+ ClassCastException("This collection only supports Strings.");
+ return c.contains(key);
+ }
+
+ /**
+ * Blocks the removal of all elements in the specified
+ * collection from the collection.
+ *
+ * @param coll the collection of elements to remove.
+ * @return true if the elements were removed.
+ * @throws NullPointerException if the collection is null.
+ * @throws NullPointerException if any collection entry is null.
+ * @throws ClassCastException if any collection entry is not a String.
+ */
+ public boolean removeAll(Collection<?> coll)
+ {
+ for (Object o: coll)
+ {
+ if (o == null)
+ throw new
+ NullPointerException("This collection does not support " +
+ "null values.");
+ if (!(o instanceof String))
+ throw new
+ ClassCastException("This collection only supports Strings.");
+ }
+ return c.removeAll(coll);
+ }
+
+ /**
+ * Blocks the retention of all elements in the specified
+ * collection from the collection.
+ *
+ * @param c the collection of elements to retain.
+ * @return true if the other elements were removed.
+ * @throws NullPointerException if the collection is null.
+ * @throws NullPointerException if any collection entry is null.
+ * @throws ClassCastException if any collection entry is not a String.
+ */
+ public boolean retainAll(Collection<?> coll)
+ {
+ for (Object o: coll)
+ {
+ if (o == null)
+ throw new
+ NullPointerException("This collection does not support " +
+ "null values.");
+ if (!(o instanceof String))
+ throw new
+ ClassCastException("This collection only supports Strings.");
+ }
+ return c.containsAll(coll);
+ }
+
+ /**
+ * This simply calls the same method on the wrapped
+ * collection.
+ *
+ * @return the size of the underlying collection.
+ */
+ public int size()
+ {
+ return c.size();
+ }
+
+ } // class EnvironmentCollection<String>
+
+ /**
+ * This is a specialised <code>HashMap</code>, which
+ * prevents the addition or querying of anything other than
+ * <code>String</code> objects.
+ *
+ * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
+ */
+ static class EnvironmentMap
+ extends HashMap<String,String>
+ {
+
+ /**
+ * Cache the entry set.
+ */
+ private transient Set<Map.Entry<String,String>> entries;
+
+ /**
+ * Cache the key set.
+ */
+ private transient Set<String> keys;
+
+ /**
+ * Cache the value collection.
+ */
+ private transient Collection<String> values;
+
+ /**
+ * Constructs a new empty <code>EnvironmentMap</code>.
+ */
+ EnvironmentMap()
+ {
+ super();
+ }
+
+ /**
+ * Constructs a new <code>EnvironmentMap</code> containing
+ * the contents of the specified map.
+ *
+ * @param m the map to be added to this.
+ * @throws NullPointerException if a key or value is null.
+ * @throws ClassCastException if a key or value is not a String.
+ */
+ EnvironmentMap(Map<String,String> m)
+ {
+ super(m);
+ }
+
+ /**
+ * Blocks queries containing a null key or one which is not
+ * of type <code>String</code>. All other queries
+ * are forwarded to the superclass.
+ *
+ * @param key the key to look for in the map.
+ * @return true if the key exists in the map.
+ * @throws NullPointerException if the specified key is null.
+ */
+ public boolean containsKey(Object key)
+ {
+ if (key == null)
+ throw new
+ NullPointerException("This map does not support null keys.");
+ if (!(key instanceof String))
+ throw new
+ ClassCastException("This map only allows queries using Strings.");
+ return super.containsKey(key);
+ }
+
+ /**
+ * Blocks queries using a null or non-<code>String</code> value.
+ * All other queries are forwarded to the superclass.
+ *
+ * @param value the value to look for in the map.
+ * @return true if the value exists in the map.
+ * @throws NullPointerException if the specified value is null.
+ */
+ public boolean containsValue(Object value)
+ {
+ if (value == null)
+ throw new
+ NullPointerException("This map does not support null values.");
+ if (!(value instanceof String))
+ throw new
+ ClassCastException("This map only allows queries using Strings.");
+ return super.containsValue(value);
+ }
+
+ /**
+ * Returns a set view of the map entries, with the same
+ * provisions as for the underlying map.
+ *
+ * @return a set containing the map entries.
+ */
+ public Set<Map.Entry<String,String>> entrySet()
+ {
+ if (entries == null)
+ entries = super.entrySet();
+ return entries;
+ }
+
+ /**
+ * Blocks queries containing a null or non-<code>String</code> key.
+ * All other queries are passed on to the superclass.
+ *
+ * @param key the key to retrieve the value for.
+ * @return the value associated with the given key.
+ * @throws NullPointerException if the specified key is null.
+ * @throws ClassCastException if the specified key is not a String.
+ */
+ public String get(Object key)
+ {
+ if (key == null)
+ throw new
+ NullPointerException("This map does not support null keys.");
+ if (!(key instanceof String))
+ throw new
+ ClassCastException("This map only allows queries using Strings.");
+ return super.get(key);
+ }
+
+ /**
+ * Returns a set view of the keys, with the same
+ * provisions as for the underlying map.
+ *
+ * @return a set containing the keys.
+ */
+ public Set<String> keySet()
+ {
+ if (keys == null)
+ keys = new EnvironmentSet(super.keySet());
+ return keys;
+ }
+
+ /**
+ * Associates the given key to the given value. If the
+ * map already contains the key, its value is replaced.
+ * The map does not accept null keys or values, or keys
+ * and values not of type {@link String}.
+ *
+ * @param key the key to map.
+ * @param value the value to be mapped.
+ * @return the previous value of the key, or null if there was no mapping
+ * @throws NullPointerException if a key or value is null.
+ * @throws ClassCastException if a key or value is not a String.
+ */
+ public String put(String key, String value)
+ {
+ if (key == null)
+ throw new NullPointerException("A new key is null.");
+ if (value == null)
+ throw new NullPointerException("A new value is null.");
+ if (!(key instanceof String))
+ throw new ClassCastException("A new key is not a String.");
+ if (!(value instanceof String))
+ throw new ClassCastException("A new value is not a String.");
+ return super.put(key, value);
+ }
+
+ /**
+ * Removes a key-value pair from the map. The queried key may not
+ * be null or of a type other than a <code>String</code>.
+ *
+ * @param key the key of the entry to remove.
+ * @return the removed value.
+ * @throws NullPointerException if the specified key is null.
+ * @throws ClassCastException if the specified key is not a String.
+ */
+ public String remove(Object key)
+ {
+ if (key == null)
+ throw new
+ NullPointerException("This map does not support null keys.");
+ if (!(key instanceof String))
+ throw new
+ ClassCastException("This map only allows queries using Strings.");
+ return super.remove(key);
+ }
+
+ /**
+ * Returns a collection view of the values, with the same
+ * provisions as for the underlying map.
+ *
+ * @return a collection containing the values.
+ */
+ public Collection<String> values()
+ {
+ if (values == null)
+ values = new EnvironmentCollection(super.values());
+ return values;
+ }
+
+ }
+
+ /**
+ * This is a specialised <code>Set</code>, providing
+ * the necessary provisions for the collections used by the
+ * environment variable map. Namely, it prevents
+ * modifications and the use of queries with null
+ * or non-<code>String</code> values.
+ *
+ * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
+ */
+ private static class EnvironmentSet
+ extends EnvironmentCollection
+ implements Set<String>
+ {
+
+ /**
+ * Constructs a new environment set, which
+ * wraps the elements of the supplied set.
+ *
+ * @param set the set to use as a base for
+ * this set.
+ */
+ public EnvironmentSet(Set<String> set)
+ {
+ super(set);
+ }
+
+ /**
+ * This simply calls the same method on the wrapped
+ * collection.
+ *
+ * @param obj the object to compare with.
+ * @return true if the two objects are equal.
+ */
+ public boolean equals(Object obj)
+ {
+ return c.equals(obj);
+ }
+
+ /**
+ * This simply calls the same method on the wrapped
+ * collection.
+ *
+ * @return the hashcode of the collection.
+ */
+ public int hashCode()
+ {
+ return c.hashCode();
+ }
+
+ } // class EnvironmentSet<String>
+
} // class System
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