EnhancedProperties is an improved way to read *.properties-files in Java. It handles reading (and soon writing) files for you, so you don't need to worry about your Input/Output-Streams, closing files etc. There are even methods to parse the data into the most common datatypes. This library is especially useful, if you have a large amount of properties.

<dependency>
  <groupId>de.felixsfd</groupId>
  <artifactId>enhancedproperties</artifactId>
  <version>1.1.0</version>
</dependency>

For reading a double value from a local properties file, you'd do something like this:

Properties properties = new Properties();
try (FileInputStream fis = new FileInputStream(new File("my.properties"))) {
  properties.load(fis);
}

String strValue = properties.getProperty("someNumber", "0.0");
double doubleValue;
try {
  doubleValue = Double.parseDouble(strValue);
} catch (NumberFormatException e) {
  doubleValue = 0.0;
}

This might be nice an quick in some cases, but if you have lots of properties and read them very often, this can be quite annoying.

If you don't have many different keys in you file, you can create an anonymous class of EnhancedPropertiesInFile, EnhancedPropertiesInResources or EnhancedPropertiesInFileOrResources. This is not the recommended way, but it should work, too.

EnhancedPropertiesInFile propertiesInFile = new EnhancedPropertiesInFile("my.properties") {};
double doubleValue = propertiesInFile.getDouble("someNumber", 0.0);

This is the recommended way of using EnhancedProperties.

To read the properties for your application, you'll need to create a subclass of EnhancedPropertiesInFile, EnhancedPropertiesInResources or EnhancedPropertiesInFileOrResources. In this example, we need EnhancedPropertiesInFile.

public class MyProperties extends EnhancedPropertiesInFile {
  protected MyProperties() throws IOException {
    super("my.properties");
  }

  public double getDoubleValue(double defaultValue) {
    return super.getDouble("doubleValue", defaultValue);
  }
}

Since the MyProperties-class contains the file-path and handles parsing the double as well, we can now access the value like this:

MyProperties myProperties = new MyProperties();
double doubleValue = myProperties.getDoubleValue(0.0);

To read a file from your application's resources, you can follow the instructions of the "basic example". Just change the superclass for MyProperties from EnhancedPropertiesInFile to EnhancedPropertiesInResources.

public class MyProperties extends EnhancedPropertiesInResources {
  protected MyProperties() throws IOException {
    super("my.properties");
  }

  public double getDoubleValue(double defaultValue) {
    return super.getDouble("doubleValue", defaultValue);
  }
}

For complex use-cases, you can read files from file-system and the application's resources at the same time. If a key is present in both files, the value from the preferred file will be used. This is useful, if you ship default properties within the resources of the application but you wan't to override some of the values.

In this example, we assume, that the default properties are stored in the resources-root directory and the custom properties in /home/user/application/my.properties. The values of the file in the file-system should be preferred over the values in the resources.

@ReadRule(preferredLocation = ReadRule.Location.FILE)
public class MyProperties extends EnhancedPropertiesInResources {
  protected MyProperties() throws IOException {
    super("/home/user/application/my.properties", "my_default.properties");
  }

  public double getDoubleValue(double defaultValue) {
    return super.getDouble("doubleValue", defaultValue);
  }
}

If you want the properties in the resources to be the preferred file, just change the annotation to @ReadRule(preferredLocation = ReadRule.Location.RESOURCES).