Java Syntax Part I Comments Identifiers Primitive Data

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) account. Number length 1 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; int j = 6; i = j*3 // change i to 5 // create an integer variable j // 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; j += 5; j++; // as before // same as j = j + 1; // same as j = j + 5; // same as j = j + 1;