Copyright © 2003 Pearson Education, Inc. Slide 2-1 Problem Solving with Java™ Second Edition Elliot Koffman and Ursula Wolz Copyright © 2003 Pearson Education, Inc. Prepared by: Elliot Koffman, Temple University and Dorina Petriu, Carleton University

Copyright © 2003 Pearson Education, Inc. Slide Processing numeric data Arithmetic operatorMeaningExample + Addition is is 7.0 – Subtraction is is 3.0 * Multiplication 5 * 2 is * 2.0 is 10.0 / Division 5.0 / 2.0 is / 2.0 is / 2 is / 2 is 2 (integer division) % Remainder 7 % 4 is 3 (use only w/ int) 4 % 7 is 4

Copyright © 2003 Pearson Education, Inc. Slide 2-3 Integer Division and Remainder int data type + - * / = (assignment) % Used only with integers, gives remainder Examples of integer division and remainder 15 / 3 = 5, 15 % 3 = 0 15 / 2 = 7, 15 % 2 = 1 2 / 15 = 0, 2 % 15 = / 100 = 2, 299 % 100 = 99

Copyright © 2003 Pearson Education, Inc. Slide 2-4 Statements and Expressions Statement: an instruction that performs an operation. There are two kinds of statements: –data declarations - tell the Java compiler what kind of storage locations to allocate –executable statements - instruct the computer how to process the information in storage Expression: Java code that produces a result. Expressions are used mostly as parts of statements.

Copyright © 2003 Pearson Education, Inc. Slide 2-5 Assignment Statement Form: variable = expression ; Example: x = y + z; Interpretation: If variable is declared as a primitive type, the value of the expression is stored in variable. If variable is a declared as a class type, a reference to the object formed by expression is stored in variable. The previous value of variable is lost. The expression can be a variable, a constant, a literal, a method call returning a value, or a combination of the above connected by appropriate operators (such as +, -, * and / ).

Copyright © 2003 Pearson Education, Inc. Slide 2-6 Assignment Compatability In an assignment statement, the value of the expression must be assignment compatible with the variable, meaning that: Either the data types of the expression and variable are the same, or The expression’s type can be converted to the variable’s type. If this condition is met, the conversion (which is named assignment conversion) is performed automatically.

Copyright © 2003 Pearson Education, Inc. Slide 2-7 Effect of assignment statements sum = sum + item; before assignment: sum = 25.0; item = 5.0 after assignment: sum = 30.0; item = 5.0 newx = -x; before assignment: newx = 0.0; x = ; after assignment: newx = 5.123; x = ;

Copyright © 2003 Pearson Education, Inc. Slide 2-8 Data Type of Arithmetic Operation The type of the result of an arithmetic operation is double if an operand is type double. e.g., is 3.0 If both operands are type int, then the result is type int. e.g., 1 / 2 is 0.

Copyright © 2003 Pearson Education, Inc. Slide 2-9 Mixed-type assignments Mixed-type assignment statement: the assignment of an expression of one type to a variable of another type. Assignment conversion: automatic conversion of the expression value (after the expression was completely evaluated) to the variable type. Such a conversion must be a widening one (e.g., from int to double). int m = 3; int n = 2; double x, y; y = m + n; assignment conversion: y becomes 5.0 (not 5) x = y + m / n; m / n is 1 (not 1.5), is 6.0, assign 6.0 to x Example of invalid assignments due to possible loss of the fractional part (narrowing conversion is not allowed) int count; count = 3.6; invalid: can’t assign double to int count = count + 1.0; invalid: expr. result is double Error: Incompatible type for =. Explicit cast needed to convert double to int.

Copyright © 2003 Pearson Education, Inc. Slide 2-10 Type casting Casting: the most general form of conversion in Java. A cast is a Java operator specified by a type in parentheses, that is applied to the value of an expression. Type casting syntax: Form: (type) valueExample: double cost; int dollars; dollars = (int) cost; Interpretation: The cast in the example creates an int value by converting cost to an integer (which truncates any fractional part). The content of cost remains unchanged. More type casting examples: int count; count = (int) 3.6; int m = 7; int n = 2; double x; x = (double) m / n; int m = 7; int n = 2; double x; x = (double) (m /n); the cast operator creates a double value (i.e., 7.0 ) n is converted to a double by arithmetic promotion division produces the result 3.5, which is assigned to x the cast operator creates an int value (i.e. 3 ), which is assigned to count the integer division 7 / 2 gives the result 3 the cast operator creates a double value (i.e., 3.0 ), which is assigned to x

Copyright © 2003 Pearson Education, Inc. Slide 2-11 Rules for Evaluating Expressions Parentheses rule: Evaluate expressions in parentheses separately. Evaluate nested parens from the inside out. Operator precedence rule: Operators in the same expression are evaluated in the order determined by their precedence (from the highest to the lowest). OperatorPrecedence Left associative rule: Operators in the same expression and at the same precedence level are evaluated in left-to-right order. method callhighest precedence - (unary) new, type cast *, /, % +, - (binary) = lowest precedence

Copyright © 2003 Pearson Education, Inc. Slide 2-12 Evaluation of z – (a + b / 2) * w / y z - (a + b / 2) * w / y Operator, reason evaluated --/--- /, parens and precedence , parens *-- *, precendence, left assoc /-- /, precedence

Copyright © 2003 Pearson Education, Inc. Slide 2-13 Mathematical Formulas in Java a = bc not valid Java syntax –insert * Operator a = b * c; m = y - b x - a –insert ( ) and /m = (y - b) / (x - a);

Copyright © 2003 Pearson Education, Inc. Slide 2-14 Class TwoNumbers public class TwoNumbers { public static void main(String[] args) { double num1 = 8; double num2 = 6; System.out.println("First number is " + num1); System.out.println("Second number is " + num2); System.out.println("Sum is " + (num1 + num2)); System.out.println("Difference is " + (num1 - num2)); System.out.println("Product is " + (num1 * num2)); System.out.println("Quotient is " + (num1 / num2)); } }

Copyright © 2003 Pearson Education, Inc. Slide 2-15 Sample run of class TwoNumbers