Properties file are important as they help in building configurable system. For example you many not to hard code your username and passwords in the code, as those access credentials might change from environment to environment. You may also want to put the configurable parameters in the properties file.
A properties file can be read either from class path or form a file system,
Reading from classpath
Let's assume we have a file credentials.properties in the classpath
To read the file, us the following code:
//Read the properties file in a reader. If you are in a static method replace this.getClass with
String fileName = "credentials.properties";
Reader reader = new BufferedReader(new InputStreamReader(
//Instantiate a properties object and load the reader
Properties properties = new Properties();
//Print the properties
System.out.println("Key: " + pair.getKey() +
" Value: " + pair.getValue());
This will print
Key: key2 Value: value2
Key: key1 Value: value1
The properties are loaded in a set.
Reading properties file from File System
If you want to read the properties from a file system, change the file reading code as follows. Rest of the code remains same.
// Read the properties file in a reader
String fileName = "<Location of File path>/credentials.properties";
Reader reader = new BufferedReader(new FileReader(fileName));