step 3: avoided memory loss by applying singleton design pattern

premaseem · premaseem · commit 68dabebf14e1 · 2018-01-09T13:23:24.000-06:00
diff --git a/src/com/premaseem/Calculator.java b/src/com/premaseem/Calculator.java
@@ -6,12 +6,22 @@
 @link: https://premaseem.wordpress.com/category/computers/design-patterns/
 */
 public class Calculator {
-static int num = 0;
-    public Calculator(){
+    static int num = 0;
+    private static Calculator instance = null;
+
+    public static Calculator getInstance(){
+        if (instance == null){
+            instance = new Calculator();
+        }
+        return instance;
+    }
+
+    private Calculator () {
         num++;
-        System.out.println(num+ " wasting memory with new object");
+        System.out.println(num + " wasting memory with new object");
     }
-    public Integer add(Integer sum, Integer number){
+
+    public Integer add (Integer sum, Integer number) {
         return sum + number;
     }
 }
diff --git a/src/com/premaseem/Client.java b/src/com/premaseem/Client.java
@@ -16,7 +16,7 @@ public static void main (String[] args) {
     private static Integer calculateSum () {
         Integer sum = 0;
         for (int i =0; i< 1000; i++){
-            Calculator calc = new Calculator();
+            Calculator calc = Calculator.getInstance();
             sum = calc.add(sum,i);
         }
         return sum;

Original file line number	Diff line number	Diff line change
`@@ -16,7 +16,7 @@ public static void main (String[] args) {`
`16`	`16`	`private static Integer calculateSum () {`
`17`	`17`	`Integer sum = 0;`
`18`	`18`	`for (int i =0; i< 1000; i++){`
`19`		`- Calculator calc = new Calculator();`
	`19`	`+ Calculator calc = Calculator.getInstance();`
`20`	`20`	`sum = calc.add(sum,i);`
`21`	`21`	`}`
`22`	`22`	`return sum;`