Challenge 40.

null value regarding instanceof.

Author: JavaZakariae

src/main/java/challenge31_40/Challenge_40.java

@@ -0,0 +1,35 @@
+package challenge31_40;
+
+import java.util.ArrayList;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ *  If we son't initialize the t instance variable, it will be equals to null;
+ *  the null value can create many problems as the example below
+ *
+ */
+public class Challenge_40 <T> {
+
+    T t;
+
+    public static void main( String[] args ) {
+        doStuffWithNullValue(null);
+        
+        if (null instanceof Object)
+            System.out.println("null is instance of object");
+        if(null instanceof AtomicInteger)
+            System.out.println("null is instance of AtomicInteger");
+        if(null instanceof StackOverflowError)
+            System.out.println("null is instance of StackOverflowError");
+        if (new ArrayList<>() instanceof Cloneable)
+            if (new String() instanceof CharSequence)
+                if (new Challenge_40<>().t instanceof Object)
+                    System.out.println("Exception");
+
+    }
+
+    private static void doStuffWithNullValue( Integer number ) {
+        if (number instanceof Integer)
+            System.out.println("Do some logic .....");
+    }
+}