b = a++ [add, keep initial a]; ++a [add, get new 'a']

Week 7: Enum, Generic Type, Streams, write to file, class diagram/13A. Expression Statements+++

@@ -0,0 +1,92 @@
+Let's return to Java's 'expression statements' for a moment. 
+So far, we have mainly used expression statements 
+to increase and decrease the value of a variable in a statement, 
+for example in a 'for statement':
+
+// i++ increases the value of i by one
+for (int i=0; i<10; i++) {
+    System.out.println("i: " + i);
+}
+
+
+As the name suggests, incrementing and decrementing also works as part of an expression. 
+Although its use in this way may not be recommended, it's good to be aware of how the change works.
+
+
+
+
+=========================================
+
+
+
+The idea is that if the increment or decrement is after the variable, 
+- the value is FIRST READ into the expression 
+- and THEN CHANGED.
+
+
+So the statement
+
+int b = a++;
+ 
+means that b INITIALLY GETS the CURRENT VALUE of a. 
+THEN the value of 'a' is INCREASED by one. 
+
+
+
+For example,
+
+// from above
+int a = 5;
+int b = a++;
+System.out.println("The value of a is " + a + " and b is " + b);
+
+
+// explained later below
+a = 5;
+b = ++a;
+System.out.println("The value of a is " + a + " amd b is " + b);
+
+The program prints:
+The value of a is 6 and b is 5 => a++ so 'a' increased from 5 to 6. BUT 'b' RETAINS INITIAL 'a' value of 5
+The value of a is 6 and b is 6 => ++a so 'a' increased from 5 to 6. THEN 'b' GETS NEW 'a' value of 6
+ 
+
+
+
+
+
+=========================================
+
+
+
+If the VALUE CHANGE is in front of the variable, 
+it is performed BEFORE the EXPRESSION is EVALUATED. 
+
+So the expression
+
+int b = ++a;
+
+
+...means that the value of '
+- a' is first increased by one and 
+- then b gets the changed value. 
+
+
+For example,
+
+a = 5;
+b = a--;
+System.out.println("The value of a is " + a + " and b is " + b);
+
+a = 5;
+b = --a;
+System.out.println("The value of a is " + a + " and b is " + b);
+ 
+
+The program prints:
+The value of a is 4 and b is 5 => a-- so 'a' decreases from 5 to 4. BUT 'b' keeps initial 'a' which is 5
+The value of a is 4 and b is 4 => --a so 'a' decreases from 5 to 4. THEN 'b' gets new 'a' which is 4
+
+
+
+