1. 1 Number Types  Every value in Java is either: 1.a reference to an object or 2.one of the eight primitive types  eight primitive types: a.four integer types b.two floating-point types c.two other

2. 2 Primitive Types TypeNumeric Range and PrecisionMemory Whole Numbers byte-128 … 1271 byte (8 bits) short-32,768 … 32,7672 bytes (16 bits) int-2,147,483,648 … 2,147,483,647 (little over 2 billion) 4 bytes (32 bits) long-9,223,372,036,854,775,808 … 9,223,372,036,854,775,807 (just under 19 digits) 8 bytes (64 bits) Decimal Numbers float7 digits of precision, exponent of 38, i.e., 1.234567*10 38 4 bytes (32 bits) double15 digits of precision, exponent of 3088 bytes (64 bits) Other Stuff boolean0 is false, 1 is true1 bit charUnicode: potential to represent over 32,000 characters2 Bytes (16 bits)

3. 3 Number Literals Any number that appears in your code:  If it has a decimal, it is floating point (double)  If not, it is an integer (int)

4. 4 Number Literals

5. 5 Overflow The result of a computation exceeds the range for the number type  Example int n = 1000000; System.out.println(n * n); // Prints –727379968, which is clearly wrong

6. 6 Overflow int n = 1000000; System.out.println(n * n); // Prints –727379968, which is clearly wrong  10 12 is larger that the largest int The result is truncated, wrap around effect No warning is given  Solution: use long instead, but even long can truncate.

7. 7 Rounding Errors  Floating-point numbers have limited precision. Not every value can be represented precisely, and roundoff errors can occur.  Example: double f = 4.35; System.out.println(100 * f); // Prints 434.99999999999994

8. 8 Constants: final  Use symbolic names for all values, even those that appear obvious.  A final variable is a constant Once its value has been set, it cannot be changed  Named constants make programs easier to read and maintain.  Convention: use all-uppercase names for constants: final double QUARTER_VALUE = 0.25;

9. 9 Constants: final final double QUARTER_VALUE = 0.25; final double DIME_VALUE = 0.1; final double NICKEL_VALUE = 0.05; final double PENNY_VALUE = 0.01; payment = dollars + quarters * QUARTER_VALUE + dimes * DIME_VALUE + nickels * NICKEL_VALUE + pennies * PENNY_VALUE;

10. 10 Constants: static final  If constant values are needed in several methods, Put them with your instance variables Tag them as static and final  The static reserved word means that the constant belongs to the class  Give static final constants public access to enable other classes to use them.

11. 11 Constants: static final  Declaration of constants in the Math class public class Math { public static final double E = 2.7182818284590452354; public static final double PI = 3.14159265358979323846; }  Using a constant double circumference = Math.PI * diameter;

12. 12 Section_1/CashRegister.javaCashRegister.java 4 public class CashRegister 5 { 6 public static final double QUARTER_VALUE = 0.25; 7 public static final double DIME_VALUE = 0.1; 8 public static final double NICKEL_VALUE = 0.05; 9 public static final double PENNY_VALUE = 0.01; 10 11 private double purchase; 12 private double payment; 13 17 public CashRegister() 18 { 19 purchase = 0; 20 payment = 0; 21 } 22 Continued

13. 13 Section_1/CashRegister.javaCashRegister.java 27 public void recordPurchase(double amount) 28 { 29 purchase = purchase + amount; 30 } 31 40 public void receivePayment(int dollars, int quarters, 41 int dimes, int nickels, int pennies) 42 { 43 payment = dollars + quarters * QUARTER_VALUE 44+ dimes * DIME_VALUE + nickels * NICKEL_VALUE 45 + pennies * PENNY_VALUE; 46 } 47 Continued

14. 14 Section_1/CashRegister.javaCashRegister.java 47 /** 48 Computes the change due and resets the machine for the next customer. 49 @return the change due to the customer 50 */ 51 public double giveChange() 52 { 53 double change = payment - purchase; 54 purchase = 0; 55 payment = 0; 56 return change; 57 } 58 }

15. 15 Section_1/CashRegisterTester.javaCashRegisterTester.java 4 public class CashRegisterTester 5 { 6 public static void main(String[] args) 7 { 8 CashRegister register = new CashRegister(); 9 10 register.recordPurchase(0.75); 11 register.recordPurchase(1.50); 12 register.receivePayment(2, 0, 5, 0, 0); 13 System.out.print("Change: "); 14 System.out.println(register.giveChange()); 15 System.out.println("Expected: 0.25"); 16 17 register.recordPurchase(2.25); 18 register.recordPurchase(19.25); 19 register.receivePayment(23, 2, 0, 0, 0); 20 System.out.print("Change: "); 21 System.out.println(register.giveChange()); 22 System.out.println("Expected: 2.0"); 23 } 24 } Program Run: Change: 0.25 Expected: 0.25 Change: 2.0 Expected: 2.0

16. 16 Arithmetic Operators  Four basic operators: addition: + subtraction: - multiplication: * division: /  Expression: combination of variables, literals, operators, and/or method calls  Parentheses control the order of the computation (a + b) / 2  Multiplication and division have a higher precedence than addition and subtraction a + b / 2

17. 17 Arithmetic Operators  Mixing integers and floating-point values in an arithmetic expression yields a floating-point value 7 + 4.0 is the floating-point value 11.0

18. 18 Increment and Decrement  The ++ operator adds 1 to a variable (increments) counter++; // Adds 1 to the variable counter  The -- operator subtracts 1 from the variable (decrements) counter--; // Subtracts 1 from counter

19. 19 Integer Division and Remainder  Division works as you would expect, as long as at least one of the numbers is a floating-point number.  Example: all of the following evaluate to 1.75 7.0 / 4.0 7 / 4.0 7.0 / 4

20. 20 Integer Division and Remainder  If both numbers are integers, the result is an integer. The remainder is discarded 7 / 4 evaluates to 1  Use % operator to get the remainder with (pronounced “modulus”, “modulo”, or “mod”) 7 % 4 is 3

21. 21 Integer Division and Remainder int pennies = 1729  Obtain the dollars through an integer division by 100 int dollars = pennies / 100; // Sets dollars to 17  To obtain the remainder, use the % operator int cents = pennies % 100; // Sets cents to 29

22. 22 Integer Division and Remainder

23. 23 Powers and Roots  Math class contains methods sqrt and pow to compute square roots and powers  To take the square root of a number, use Math.sqrt; for example Math.sqrt(x)  To compute x n, you write Math.pow(x, n)  To compute x 2 it is significantly more efficient simply to compute x * x

24. 24 Powers and Roots  In Java, can be represented as b * Math.pow(1 + r / 100, n)

25. 25 Analyzing an Expression

26. 26 Mathematical Methods

27. 27 Mathematical Methods

28. 28 Converting Floating-Point Numbers to Integers - Cast  The compiler disallows the assignment of a double to an int because it is potentially dangerous The fractional part is lost The magnitude may be too large This is an error double balance = total + tax; int dollars = balance; // Error: Cannot assign double to int

29. 29 Converting Floating-Point Numbers to Integers - Cast  Use the cast operator (int) to convert a convert floating-point value to an integer. double balance = total + tax; int dollars = (int) balance;  Cast discards fractional part  You use a cast (typeName) to convert a value to any different type.

30. 30 Converting Floating-Point Numbers to Integers - Rounding  Math.round converts a floating-point number to nearest integer: long rounded = Math.round(balance);  If balance is 13.75, then rounded is set to 14.

31. 31 Arithmetic Expressions