Java Syntax Part I Comments Identifiers Primitive Data Types Assignment

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 */

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

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 }

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.

Java Syntax -- Identifiers (example) accountNumber length1 length_2

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;

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

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;