When I re-pick-up Java, after having dealt with really different programming languages in the months before, I encounter these moments of “damn-you-know-this”. So when I came back to java this time, I recorded my top five missing Java pieces:

1. Conversion from String to Integer

   String example=“1”;
   int value = Integer.parseInt( example );
   

   It is NOT:

   Integer.getInteger( example );

   The getInteger method trys to

   Determines the integer value of the system property with the specified name.

2. The ? – Operator The Java ternary operator (sometimes referred to as the “questionmark operator”) is an elegeant way to deal with boolean (TRUE / FALSE) decisions or assignments in the programming world. The ternary operator differs from an if-else statement due to the fact that it is an expression that returns a value. While the if-else structure  executes a statement. The following Example assigns the maximum Value of two ints to a new variable:

   int a = 5;
   int b = 10;
   int max  = (a > b ? a : b);
   

3. instanceof and isInstance The binary operator instanceof checks if an object is a member of a class:

   SampleObject sample = new SampleObject();
   if(sample instanceof SampleObject) {
   ...
   }
   

   Unfortunately though it is not possible to set the type (which the object is tested against) at runtime and use for example a string at the leftside of the instanceof operator:

   SampleObject sample = new SampleObject();
   String sampleStr = "sampleObject";
   

   if(sample instanceof sampleStr) {

   ...
   }
   

   At runtime it is possible though to check the type of an object with the isInstance method:

   // the object where we know what kind of type it is
   SampleObject sampleold = new SampleObject();
   
   // our "unknown" type object
   Object samplenew = new SampleObject();
   
   if(sampleold.getClass().isInstance(samplenew)) {
   ...
   }
   
   

   Attention to the switch of the arguments between instanceof and isInstance !

4. Comparator
   
   If I write a Comparator Object I usually implement Comparator<T> and then override  int compare(T t1, T t2). To implement a proper working compare method the following “handrules” apply:
   1. (t1 < t2) ->  return a negative value
   2. (t1 == t2) -> return zero
   3. (t1 > t2) -> return a positive value

   The <, ==, > do NOT have to refer to the standard smaller, greater, etc operators !