THE PACKAGE JAVA.UTIL

java.util.Properties

21.6

21.6 The Class

java.util.Properties

A

Properties

 table is a kind of

Hashtable

 with two functionality extensions

and with the restriction that keys and elements must be strings. First, there are

methods for reading entries into the table from an input stream and writing all the

entries in the table to an output stream. Second, a

Properties

 table may refer to

another

Properties

 table that provides default values. The

getProperty

method is much like the

get

 method ( 21.4.3), but if an entry is not found in this

table, then the defaults table is searched (and that defaults table may itself refer to

another defaults table, and so on, recursively).

public class Properties extends Hashtable {

protected Properties defaults;

public Properties();

public Properties(Properties defaults);

public String getProperty(String key);

public String getProperty(String key, String defaultValue);

public Enumeration propertyNames();

public void load(InputStream in) throws IOException;

public void save(OutputStream out, String header);

public void list(PrintStream out);

}

21.6.1

protected Properties defaults;

If the

defaults

 field is not

null

, it is another

Properties

 table that provides

default values for this

Properties

 table.

21.6.2

public Properties()

This constructor initializes a newly created

Properties

 table so that it has no

defaults table. Initially, there are no entries in the newly created table.

21.6.3

public Properties(Properties defaults)

This constructor initializes a newly created

Properties

 table so its defaults table

is

defaults

. The argument

defaults

 may be

null

, in which case the newly cre 

ated

Properties

 table will not have a defaults table. Initially, there are no entries

in the newly created table.

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