There is an old rule about programming and not only about it, if something looks beautiful, then most probably it is the right way to do.
This approach does not look good, from my point of view.
The first thing:
Do not declare constants in interfaces. It violates the incapsulation approach. Check this article please: http://en.wikipedia.org/wiki/Constant_interface
The second thing:
Use a prefix for name part of your properties which are somehow special, let say: key_
And when you load your properties file, iterate over keys and extract keys with name that starts with key_ and use values of these keys as you planned to use those constants in your question.
UPDATE
Assume, we generate a huge properties file upon compilation process, using our Apache Ant script.
For example, let's properties file (myapp.properties) looks like that:
key_A = Apple
key_B = Banana
key_C = Cherry
anotherPropertyKey1 = blablabla1
anotherPropertyKey2 = blablabla2
our special properties which we want to handle have key names start with key_ prefix.
So, we write the following code (please note, it is not optimized, it is just proof of concept):
package propertiestest;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Properties;
import java.util.Set;
public class PropertiesTest {
public static void main(String[] args) throws IOException {
final String PROPERTIES_FILENAME = "myapp.properties";
SpecialPropertyKeysStore spkStore =
new SpecialPropertyKeysStore(PROPERTIES_FILENAME);
System.out.println(Arrays.toString(spkStore.getKeysArray()));
}
}
class SpecialPropertyKeysStore {
private final Set<String> keys;
public SpecialPropertyKeysStore(String propertiesFileName)
throws FileNotFoundException, IOException {
// prefix of name of a special property key
final String KEY_PREFIX = "key_";
Properties propertiesHandler = new Properties();
keys = new HashSet<>();
try (InputStream input = new FileInputStream(propertiesFileName)) {
propertiesHandler.load(input);
Enumeration<?> enumeration = propertiesHandler.propertyNames();
while (enumeration.hasMoreElements()) {
String key = (String) enumeration.nextElement();
if (key.startsWith(KEY_PREFIX)) {
keys.add(key);
}
}
}
}
public boolean isKeyPresent(String keyName) {
return keys.contains(keyName);
}
public String[] getKeysArray() {
String[] strTypeParam = new String[0];
return keys.toArray(strTypeParam);
}
}
Class SpecialPropertyKeysStore filters and collects all special keys into its instance.
And you can get an array of these keys, or check whether is key present or not.
If you run this code, you will get:
[key_C, key_B, key_A]
It is a string representation of returned array with special key names.
Change this code as you want to meet your requirements.
