Java Syntax Part I

1. Java Syntax Part I Comments Identifiers Primitive Data Types Assignment

2. Java Syntax - Comments • Type 1: • begins with /* • continues till the next */ • Type 2: • begins with // • continues till the end of the line • Type 3: • begins with /**, and continues till the next */

3. Java Syntax -- comments (style) • Good programming practice • Put helpful comments • at the beginning of a big block • on the same line of certain statements • Good internal documentation is very important

4. Java Syntax -- comments (example) //--------------------------------------------------------------------------- // withdraw: withdraw money from banking_account // Input : amount = the amount of money to withdraw //---------------------------------------------------------------------------- void withdraw(float amount) { //----------- if not enough money in the account ---- … //----------- else, we have enough money in the account ---- ... }

5. Java Syntax -- Identifiers • Names of declared entities • variables, constans, labels… • Must start with a letter: [A..Z][a..z] • including _ (underscore) or $ (dollar sign) • Followed by letters or digits • Java language keywords can not be used as identifiers.

6. Java Syntax -- Identifiers (example) accountNumber length1 length_2

7. Java Syntax -- Primitive Data Types • boolean: takes only 2 values true or false • Example: boolean done = false; • char : contains a character • Example: char ch; • byte, short, int and long : Integral Types • Example: int num = 3; • float, double : Floating-Point Types • Example: float temperature = 37.6;

8. Java Syntax -- Assignment • Example using integers: int i = 2; // create an integer variable i = 5; // change i to 5 int j = 6; // create an integer variable j i = j*3 // multifply the value of j by 3 // now i = 18 i = i + 4; // NOT AN EQUATION! // i was 18, i+4=22; new i=22. • Calculate the value on the RIGHT HAND SIDE • Assign the result to the variable on the LEFT HAND SIDE

9. Java Syntax -- Assignment (Abbreviations) • Examples: j = j + 1; // as before j += 1; // same as j = j + 1; j += 5; // same as j = j + 5; j++; // same as j = j + 1;