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#Core Programming Concepts

• A program is a set of instructions that tell a computer or machine what to do

• All programming languages have keywords and syntax. These are special words that are specific to the language and are the basis of the programming language you use. Java examples:

  • primitive types: int, byte, boolean, double
  • control flow: for, while, return
  • conditional: if, else
  • OO: new, extends, implements

• Data is stored in variables

  • Java and may other programming languages have primitive types and also Object types
    • primitive type examples: int, byte, boolean, double

      int grade;

• Similar data can be grouped in collections
  • arrays, Java Collections

      java int[] grades;

• Most languages define operators which define language specific operations to be applied to variables * mathematical operators: +, -, *, / * logical operators: &&, ||, ! * conditional operators: >, <, ==, <=, >=, !=
• Most languages provide developers with the ability to add comments to the code * java single line comment: // * java comment block (can be multiline): /* ... */

      // my really helpful comment line
      /* 
         some really helpful
         and even more valuable information
         that helps others understand my code and 
         helps me remember what I was trying to do
      */

• A statement is a line of code, a specific instruction for the computer to execute. Examples:
  • declare variable

      int grade;
      int grade=90;

• assign a value to a variable

      grade=85;
      grade=grade+grade*0.1;

• Statements can be grouped together into a code block

{
      int grade=90;
      grade=grade+grade*0.1;
      calculateGrade(testAnswers);
}

• Most languages a have functions, sometimes called methods, which define a code block to be executed when it is called in a statement. Functions often take one or more parameters and often return a result

      // a statement that calls a function with one parameter and returns a value
      grade = calculateGrade(testAnswers);

      // a method or function definition
      public double calculateGrade(String[] testAnswers){
         double score = 0;
         // code statements that calculates how many answers are correct and returns a score
         // ...
         return score;
      }

• Most programming languages support conditional logic
  • if something is true, then do something, otherwise, do something else

    if(grade>=90){
       return "A";
    }
    else if(grade>=80){
       return "B";
    }
    else if(grade>=70){
       return "C";
    }
    else if(grade>=60){
       return "D";
    }
    else{
       return "F";
    }

• Most programming language support control flow:
  • examples: for loops, while loops
  • 3 parts: initialization, condition, update

    for(int i=0;i<limit;i++){
       grades[i] = calculateGrade(testAnswers[i]);
    }

    boolean done = false;
     ...
    while (!done){
       doSomething();
       done = amIDone();
    }

• Java and other OO programming languages define objects
  • an encapsulation of variables (properties) and functions (methods or behaviours)
  • model real world concepts
  • why? do to cool things
    • polymorhism, encapsulation, inheritance, etc.

    public class IPod{

        //private properties
        private Song[] playList;
        private int currentSong;

        //constructor
        public IPod(Hashtable<String,Song> playList){
           this.playList= playList;
           int currentSong = 0;
        }

        //method to play current song
        public play(){
           stream(playList[currentSong]);
        }

        //method to skip to the next song and play it
        public next(){
           currentSong = currentSong + 1;
           play();
        }
    }