Primitive data types Lecture 03 Review of Last

Primitive data types Lecture 03

Review of Last Lecture • Write a program that prints the multiplication table of 5. class Multiplication. Table { public static void main(String args[]) { // Following code shows the multiplication table of 5. System. out. println("5 x 1 = 5 "); System. out. println("5 x 2 = 10"); System. out. println("5 x 3 = 15 "); System. out. println("5 x 4 = 20"); System. out. println("5 x 5 = 25"); System. out. println("5 x 6 = 30 "); System. out. println("5 x 7 = 35"); System. out. println("5 x 8 = 40 "); System. out. println("5 x 9 = 45"); System. out. println("5 x 10 = 50"); } }

Lecture outcomes • Primitive data – – – – • • integer double string char Float Long boolean Declaration Initialisation Assignments Arithmetic operators

Example • • • 123 (int) 1. 5 (double) “Hello. World” (String) `H’ (Char) ….

Basic Definitions • Variables - A name that refers to a value. • Assignment Statement - Associate a value with a variable. • Constant: – 456—a literal numerical constant • System. out. println(456); // Java – “A Literal String Constant” • System. out. println(“My First Java”); // Java

There are eight primitive data types • Boolean, byte, char, int, double, float, long, short • In bytes, how long is the short data type? The int data type, the long data type? • In bytes, how long is the float data type? The double data type? • How long is the char data type?

Primitives Data types and Ranges PRIMITIVE SIZE IN BITS RANGE int 32 bits (4 bytes) -231 to 231 -1 -2, 147, 483, 648 to +2, 147, 483, 647 long 64 bits -- 8 bytes -263 to 263 - 1 float 32 bits- -4 bytes -+(1. 40129846432481707 e-45 to 3. 40282346638528860 e+38} double 64 +-(4. 94065645841246544 e-324 to 1. 79769313486231570 e+308) char 16 bits One character string 16 bits per char Not applicable boolean 8 bits--1 -byte True or false

Examples Type Set of values Sample literal vlues interges 99 (-12) 214748647 double Floating-point numbers 3. 14 (-1. 5) 6. 0021 1023 boolean Boolean values True or false characters ‘a’ ‘ 1’ ‘£’ ‘%’ ‘n’ String Sequence of characters “AC” ”Hello” ” 1. 5”

Variable declaration Variable name Variable type int x; x integer double d; d double char c; c character String s; s string Float f; f float

The assignment operator = declaration Variable name int x; Declare the variable x as an integer x = 36; int x = 36; Sets x to constant 36 at execution time Sets x = to the constant 36 at compile time Initializes x to 36 at the time memory is set aside for it String y; Declare the variable x as an integer y = “Hellow”; Sets y to constant “Hello” at execution time String y = “Hello”; Sets y = to the constant “Hello” at compile time Initializes x to “Hello” at the time memory is set aside for it

Initialisation • If no value is assigned prior to use, then the compiler will give an error • Java sets primitive variables to zero or false in the case of a boolean variable • All object references are initially set to null • An array of anything is an object – Set to null on declaration – Elements to zero false or null on creation

Declaration Examples int index = 1. 2; // compiler error boolean ret. Ok = 1; // compiler error double five. Fourths = 5 / 4; // no error! float ratio = 5. 8 f; // correct double five. Fourths = 5. 0 / 4. 0; // correct • 1. 2 f is a float value accurate to 7 decimal places. • 1. 2 is a double value accurate to 15 decimal places.

Declaration (Cont) int a, b, c ; b =1; a=b; c =a; System. out. print(“c= “ + c); • What is the value of a, b & c

Example Int 1. java // uninitialised data // this program will declare and print a number Public class int 3 { public static void main(String[] arguments) { int weight; System. out. println("your weight is " + weight); } } //end of program

Example Int 2. java // this program will declare and print a number class int 2 { public static void main(String[] arguments) { int weight = 68; System. out. println("your weight is " + weight); } } //end of program

Example Int 5. java // uninitialised data // this program will declare and print a number class int 5 { public static void main(String[] arguments) { int weight; weight = 65 ; //65 = weight ; System. out. println("your weight is " + weight); } } //end of program

Example String 2. java // this program will declare and print a string class string 2 { public static void main(String[] arguments) { String name = "Lahcen"; String x = "my name is "; System. out. println( x + name ); //print string x and then string name } } //end of program

Basic Mathematical Operators • * / % + - are the mathematical operators • * / % have a higher precedence than + or double my. Val = a + b % d – c * d / b; • Is the same as: double my. Val = (a + (b % d)) – ((c * d) / b);

Basic arithmetic Operators Operator Meaning Example + Addition 2+3 = 5 * Multiplication 2*3=6 - subtraction 3 -2=1 / division 4/2=2 % mod 5 % 2 = 1, 6 % 2= 0

Precedence Rules 1. Evaluate all sub-expressions in parentheses 2. Evaluate nested parentheses from the inside out 3. In the absence of parentheses or within parentheses a. Evaluate *, /, or % before + or – b. Evaluate sequences of *, /, and % operators from left to right c. Evaluate sequences of + and – operators from left to right

Built-in Math Functions in Java

Example: Calculate square root class Square. Root. Exp{ public static void main(String args[]) { int x = 25; int result = Math. sqrt(x); System. out. println(“Square root of " + x + “ is " + result); } }

Exercise • Assume that the length and width of the rectangle is 10 and 5. Write a program which compute area of the rectangle and display result on the screen.

Summary • • • Different data type Declarations Arithmetic operators Parse string to integer. Boolean operators Assignments