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Java in a Nutshell

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30.17 java.util.Properties (JDK 1.0)

This class is an extension of Hashtable that allows key/value pairs to be read from and written to a stream. The Properties class is used to implement the system properties list, which supports user customization by allowing programs to look up the value of named resources.

When you create a Properties object, you may specify another Properties object that contains default values. Keys (property names) and values are associated in a Properties object with the Hashtable method put(). Values are looked up with getProperty()--if this method does not find the key in the current Properties object, it looks in the default Properties object that was passed to the constructor method. A default value may also be specified in case the key is not found at all.

propertyNames() returns an enumeration of all property names (keys) stored in the Properties object and (recursively) also all property names stored in the default Properties object associated with it. list() prints the properties stored in a Properties object. It is useful for debugging. save() writes a Properties object to a stream. load() reads key/value pairs from a stream and stores them in a Properties object.

public class Properties extends Hashtable {
    // Public Constructors
            public Properties();
            public Properties(Properties defaults);
    // Protected Instance Variables
            protected Properties defaults;
    // Public Instance Methods
            public String getProperty(String key);
            public String getProperty(String key, String defaultValue);
            public void list(PrintStream out);
        1.1public void list(PrintWriter out);
            public synchronized void load(InputStream in) throws IOException;
            public Enumeration propertyNames();
            public synchronized void save(OutputStream out, String header);
}

Hierarchy:

Object->Dictionary->Hashtable(Cloneable, Serializable)->Properties

Passed To:

Properties(), System.setProperties(), Toolkit.getPrintJob()

Returned By:

System.getProperties()

Type Of:

Properties.defaults


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