https://openjdk.java.net/ 
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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/*
 * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
 * (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved
 *
 * The original version of this source code and documentation
 * is copyrighted and owned by Taligent, Inc., a wholly-owned
 * subsidiary of IBM. These materials are provided under terms
 * of a License Agreement between Taligent and Sun. This technology
 * is protected by multiple US and International patents.
 *
 * This notice and attribution to Taligent may not be removed.
 * Taligent is a registered trademark of Taligent, Inc.
 */

package java.util;

import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.IOException;
import java.nio.charset.MalformedInputException;
import java.nio.charset.StandardCharsets;
import java.nio.charset.UnmappableCharacterException;
import sun.security.action.GetPropertyAction;
import sun.util.PropertyResourceBundleCharset;
import sun.util.ResourceBundleEnumeration;


PropertyResourceBundle is a concrete subclass of
ResourceBundle that manages resources for a locale using a set of static strings from a property file. See ResourceBundle for more information about resource bundles. 

Unlike other types of resource bundle, you don't subclass
PropertyResourceBundle.  Instead, you supply properties
files containing the resource data.  ResourceBundle.getBundle
will automatically look for the appropriate properties file and create a
PropertyResourceBundle that refers to it. See ResourceBundle.getBundle for a complete description of the search and instantiation strategy. 

The following example shows a member of a resource
bundle family with the base name "MyResources".
The text defines the bundle "MyResources_de",
the German member of the bundle family.
This member is based on PropertyResourceBundle, and the text
therefore is the content of the file "MyResources_de.properties"
(a related example shows
how you can add bundles to this family that are implemented as subclasses
of ListResourceBundle).
The keys in this example are of the form "s1" etc. The actual
keys are entirely up to your choice, so long as they are the same as
the keys you use in your program to retrieve the objects from the bundle.
Keys are case-sensitive.



# MessageFormat pattern
s1=Die Platte \"{1}\" enthält {0}.
# location of {0} in pattern
s2=1
# sample disk name
s3=Meine Platte
# first ChoiceFormat choice
s4=keine Dateien
# second ChoiceFormat choice
s5=eine Datei
# third ChoiceFormat choice
s6={0,number} Dateien
# sample date
s7=3. März 1996





See Also:
API Note: PropertyResourceBundle can be constructed either from an InputStream or a Reader, which represents a property file. Constructing a PropertyResourceBundle instance from an InputStream requires that the input stream be encoded in UTF-8. By default, if a MalformedInputException or an UnmappableCharacterException occurs on reading the input stream, then the PropertyResourceBundle instance resets to the state before the exception, re-reads the input stream in ISO-8859-1, and continues reading. If the system property java.util.PropertyResourceBundle.encoding is set to either "ISO-8859-1" or "UTF-8", the input stream is solely read in that encoding, and throws the exception if it encounters an invalid sequence. If "ISO-8859-1" is specified, characters that cannot be represented in ISO-8859-1 encoding must be represented by Unicode Escapes as defined in section 3.3 of The Java™ Language Specification whereas the other constructor which takes a Reader does not have that limitation. Other encoding values are ignored for this system property. The system property is read and evaluated when initializing this class. Changing or removing the property has no effect after the initialization.
Implementation Requirements: The implementation of a PropertyResourceBundle subclass must be thread-safe if it's simultaneously used by multiple threads. The default implementations of the non-abstract methods in this class are thread-safe.
Since:1.1
/**
 * <code>PropertyResourceBundle</code> is a concrete subclass of
 * <code>ResourceBundle</code> that manages resources for a locale
 * using a set of static strings from a property file. See
 * {@link ResourceBundle ResourceBundle} for more information about resource
 * bundles.
 *
 * <p>
 * Unlike other types of resource bundle, you don't subclass
 * <code>PropertyResourceBundle</code>.  Instead, you supply properties
 * files containing the resource data.  <code>ResourceBundle.getBundle</code>
 * will automatically look for the appropriate properties file and create a
 * <code>PropertyResourceBundle</code> that refers to it. See
 * {@link ResourceBundle#getBundle(String, Locale, ClassLoader) ResourceBundle.getBundle}
 * for a complete description of the search and instantiation strategy.
 *
 * <p>
 * The following <a id="sample">example</a> shows a member of a resource
 * bundle family with the base name "MyResources".
 * The text defines the bundle "MyResources_de",
 * the German member of the bundle family.
 * This member is based on <code>PropertyResourceBundle</code>, and the text
 * therefore is the content of the file "MyResources_de.properties"
 * (a related <a href="ListResourceBundle.html#sample">example</a> shows
 * how you can add bundles to this family that are implemented as subclasses
 * of <code>ListResourceBundle</code>).
 * The keys in this example are of the form "s1" etc. The actual
 * keys are entirely up to your choice, so long as they are the same as
 * the keys you use in your program to retrieve the objects from the bundle.
 * Keys are case-sensitive.
 * <blockquote>
 * <pre>
 * # MessageFormat pattern
 * s1=Die Platte \"{1}\" enth&auml;lt {0}.
 *
 * # location of {0} in pattern
 * s2=1
 *
 * # sample disk name
 * s3=Meine Platte
 *
 * # first ChoiceFormat choice
 * s4=keine Dateien
 *
 * # second ChoiceFormat choice
 * s5=eine Datei
 *
 * # third ChoiceFormat choice
 * s6={0,number} Dateien
 *
 * # sample date
 * s7=3. M&auml;rz 1996
 * </pre>
 * </blockquote>
 *
 * @apiNote
 * {@code PropertyResourceBundle} can be constructed either
 * from an {@code InputStream} or a {@code Reader}, which represents a property file.
 * Constructing a {@code PropertyResourceBundle} instance from an {@code InputStream}
 * requires that the input stream be encoded in {@code UTF-8}. By default, if a
 * {@link java.nio.charset.MalformedInputException} or an
 * {@link java.nio.charset.UnmappableCharacterException} occurs on reading the
 * input stream, then the {@code PropertyResourceBundle} instance resets to the state
 * before the exception, re-reads the input stream in {@code ISO-8859-1}, and
 * continues reading. If the system property
 * {@code java.util.PropertyResourceBundle.encoding} is set to either
 * "ISO-8859-1" or "UTF-8", the input stream is solely read in that encoding,
 * and throws the exception if it encounters an invalid sequence.
 * If "ISO-8859-1" is specified, characters that cannot be represented in
 * ISO-8859-1 encoding must be represented by Unicode Escapes as defined in section
 * 3.3 of <cite>The Java&trade; Language Specification</cite>
 * whereas the other constructor which takes a {@code Reader} does not have that limitation.
 * Other encoding values are ignored for this system property.
 * The system property is read and evaluated when initializing this class.
 * Changing or removing the property has no effect after the initialization.
 *
 * @implSpec
 * The implementation of a {@code PropertyResourceBundle} subclass must be
 * thread-safe if it's simultaneously used by multiple threads. The default
 * implementations of the non-abstract methods in this class are thread-safe.
 *
 * @see ResourceBundle
 * @see ListResourceBundle
 * @see Properties
 * @since 1.1
 */
public class PropertyResourceBundle extends ResourceBundle {

    // Check whether the strict encoding is specified.
    // The possible encoding is either "ISO-8859-1" or "UTF-8".
    private static final String encoding = GetPropertyAction
        .privilegedGetProperty("java.util.PropertyResourceBundle.encoding", "")
        .toUpperCase(Locale.ROOT);

    
Creates a property resource bundle from an 
InputStream. This constructor reads the property file in UTF-8 by default. If a MalformedInputException or an UnmappableCharacterException occurs on reading the input stream, then the PropertyResourceBundle instance resets to the state before the exception, re-reads the input stream in ISO-8859-1 and continues reading. If the system property java.util.PropertyResourceBundle.encoding is set to either "ISO-8859-1" or "UTF-8", the input stream is solely read in that encoding, and throws the exception if it encounters an invalid sequence. Other encoding values are ignored for this system property. The system property is read and evaluated when initializing this class. Changing or removing the property has no effect after the initialization. 
Params:
  • stream – an InputStream that represents a property file
       to read from.
Throws:
/**
     * Creates a property resource bundle from an {@link java.io.InputStream
     * InputStream}. This constructor reads the property file in UTF-8 by default.
     * If a {@link java.nio.charset.MalformedInputException} or an
     * {@link java.nio.charset.UnmappableCharacterException} occurs on reading the
     * input stream, then the PropertyResourceBundle instance resets to the state
     * before the exception, re-reads the input stream in {@code ISO-8859-1} and
     * continues reading. If the system property
     * {@code java.util.PropertyResourceBundle.encoding} is set to either
     * "ISO-8859-1" or "UTF-8", the input stream is solely read in that encoding,
     * and throws the exception if it encounters an invalid sequence. Other
     * encoding values are ignored for this system property.
     * The system property is read and evaluated when initializing this class.
     * Changing or removing the property has no effect after the initialization.
     *
     * @param stream an InputStream that represents a property file
     *        to read from.
     * @throws IOException if an I/O error occurs
     * @throws NullPointerException if <code>stream</code> is null
     * @throws IllegalArgumentException if {@code stream} contains a
     *     malformed Unicode escape sequence.
     * @throws MalformedInputException if the system property
     *     {@code java.util.PropertyResourceBundle.encoding} is set to "UTF-8"
     *     and {@code stream} contains an invalid UTF-8 byte sequence.
     * @throws UnmappableCharacterException if the system property
     *     {@code java.util.PropertyResourceBundle.encoding} is set to "UTF-8"
     *     and {@code stream} contains an unmappable UTF-8 byte sequence.
     */
    @SuppressWarnings({"unchecked", "rawtypes"})
    public PropertyResourceBundle (InputStream stream) throws IOException {
        this(new InputStreamReader(stream,
            "ISO-8859-1".equals(encoding) ?
                StandardCharsets.ISO_8859_1.newDecoder() :
                new PropertyResourceBundleCharset("UTF-8".equals(encoding)).newDecoder()));
    }

    
Creates a property resource bundle from a 
Reader. Unlike the constructor PropertyResourceBundle(InputStream), there is no limitation as to the encoding of the input property file. 
Params:
  • reader – a Reader that represents a property file to
       read from.
Throws:
Since:1.6
/**
     * Creates a property resource bundle from a {@link java.io.Reader
     * Reader}.  Unlike the constructor
     * {@link #PropertyResourceBundle(java.io.InputStream) PropertyResourceBundle(InputStream)},
     * there is no limitation as to the encoding of the input property file.
     *
     * @param reader a Reader that represents a property file to
     *        read from.
     * @throws IOException if an I/O error occurs
     * @throws NullPointerException if <code>reader</code> is null
     * @throws IllegalArgumentException if a malformed Unicode escape sequence appears
     *     from {@code reader}.
     * @since 1.6
     */
    @SuppressWarnings({"unchecked", "rawtypes"})
    public PropertyResourceBundle (Reader reader) throws IOException {
        Properties properties = new Properties();
        properties.load(reader);
        lookup = new HashMap(properties);
    }

    // Implements java.util.ResourceBundle.handleGetObject; inherits javadoc specification.
    public Object handleGetObject(String key) {
        if (key == null) {
            throw new NullPointerException();
        }
        return lookup.get(key);
    }

    
Returns an Enumeration of the keys contained in
this ResourceBundle and its parent bundles.

See Also:
Returns:an Enumeration of the keys contained in
        this ResourceBundle and its parent bundles.
/**
     * Returns an <code>Enumeration</code> of the keys contained in
     * this <code>ResourceBundle</code> and its parent bundles.
     *
     * @return an <code>Enumeration</code> of the keys contained in
     *         this <code>ResourceBundle</code> and its parent bundles.
     * @see #keySet()
     */
    public Enumeration<String> getKeys() {
        ResourceBundle parent = this.parent;
        return new ResourceBundleEnumeration(lookup.keySet(),
                (parent != null) ? parent.getKeys() : null);
    }

    
Returns a Set of the keys contained
only in this ResourceBundle.

See Also:
Returns:a Set of the keys contained only in this
        ResourceBundle
Since:1.6
/**
     * Returns a <code>Set</code> of the keys contained
     * <em>only</em> in this <code>ResourceBundle</code>.
     *
     * @return a <code>Set</code> of the keys contained only in this
     *         <code>ResourceBundle</code>
     * @since 1.6
     * @see #keySet()
     */
    protected Set<String> handleKeySet() {
        return lookup.keySet();
    }

    // ==================privates====================

    private final Map<String,Object> lookup;
}