Singleton pattern : Singleton pattern insure only a single instance of a class can exist at given time per JVM.
There are different ways to implement Singleton pattern.
In this example I will provide you to load properties files using Singleton pattern. This implementation is not thread safe. So if you are not dealing with multi-thread you can use this implementation.
public final class PropReader { private static PropReader instance = null; static Properties prop = null; static InputStream in = null; public static String tmLocation = null; // private constructor so no other class can instanciate this private PropReader() { try { in = this.getClass().getResourceAsStream("/app.properties"); prop = new Properties(); prop.load(in); tmLocation = prop.getProperty("TM_BASE_DIRECTORY"); } catch (Exception e) { System.out.println(e); } }
// provide instance if no other instance exist
public static PropReader getInstance() throws IOException { if (instance == null) { instance = new PropReader(); } return instance; } }
How to write an immutable Class in Java
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