singleton- pattern

singleton-pattern

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+// Java program implementing Singleton class
+// with using getInstance() method
+
+// Class 1
+// Helper class
+class Singleton {
+	// Static variable reference of single_instance
+	// of type Singleton
+	private static Singleton single_instance = null;
+
+	// Declaring a variable of type String
+	public String s;
+
+	// Constructor
+	// Here we will be creating private constructor
+	// restricted to this class itself
+	private Singleton()
+	{
+		s = "Hello I am a string part of Singleton class";
+	}
+
+	// Static method
+	// Static method to create instance of Singleton class
+	public static synchronized Singleton getInstance()
+	{
+		if (single_instance == null)
+			single_instance = new Singleton();
+
+		return single_instance;
+	}
+}
+
+// Class 2
+// Main class
+class SingleTon{
+	// Main driver method
+	public static void main(String args[])
+	{
+		// Instantiating Singleton class with variable x
+		Singleton x = Singleton.getInstance();
+
+		// Instantiating Singleton class with variable y
+		Singleton y = Singleton.getInstance();
+
+		// Instantiating Singleton class with variable z
+		Singleton z = Singleton.getInstance();
+
+		// Printing the hash code for above variable as
+		// declared
+		System.out.println("Hashcode of x is "
+						+ x.hashCode());
+		System.out.println("Hashcode of y is "
+						+ y.hashCode());
+		System.out.println("Hashcode of z is "
+						+ z.hashCode());
+
+		// Condition check
+		if (x == y && y == z) {
+
+			// Print statement
+			System.out.println(
+				"Three objects point to the same memory location on the heap i.e, to the same object");
+		}
+
+		else {
+			// Print statement
+			System.out.println(
+				"Three objects DO NOT point to the same memory location on the heap");
+		}
+	}
+}