Data commit

Task/Undefined-values/Java/undefined-values-1.java

@@ -0,0 +1,3 @@
+String string = null;        // the variable string is undefined
+System.out.println(string);           //prints "null" to std out
+System.out.println(string.length());  // dereferencing null throws java.lang.NullPointerException

Task/Undefined-values/Java/undefined-values-2.java

@@ -0,0 +1,4 @@
+int i = null;      // compilation error: incompatible types, required: int, found: <nulltype>
+if (i == null) {   // compilation error: incomparable types: int and <nulltype>
+    i = 1;
+}

Task/Undefined-values/Java/undefined-values-3.java

@@ -0,0 +1,4 @@
+Integer i = null;  // variable i is undefined
+if (i == null) {
+    i = 1;
+}