1 Data types, operations, and expressions Continued l Overview l Assignment statement l Increment and Decrement operators l Short hand operators l The Math Class l Evaluating an arithmetic expression with simple math function-Example l Casting

2 Assignment Statement variable = expression; l The value of constants / variables / expression in the right side of the = operator, is assigned to the variable in the left side of the = operator. l Examples: a = 5; b = a; c = a + b; l The left hand side of the = operator must be a variable. l It cannot be a constant or an expression. l Example of an invalid assignment statement : a + b = c ;

3 Assignment Statement l Java allows multiple assignment. int start, end; int width = 100, height = 45, length = 12; start = end = 0; l By default, Java takes whole numbers to be of type int and real numbers to be of type double. However, we can append a letter at the end of a number to indicate its type. l Upper and lower case letters can be used for ‘float’ (F or f), ‘double’ (D or d), and ‘long’ (l or L, but we should prefer L): float maxGrade = 100f ; // now holds ‘100.0’ double temp = 583d ; // holds double precision float temp = 5.5 ; // ERROR! // Java treats 5.5 as a double long x = 583l ; // holds 583, but looks like 5,381 long y = 583L ; // This looks much better!

4 Increment or Decrement Operators Increment/decrement operations ( count = count +1 ) are very common in programming. Java provides operators that make these operations shorter. OperatorUse Description ++ op ++ Increments op by 1; evaluates to a value before incrementing op Increments op by 1; evaluates to a value after incrementing -- op -- Decrements op by 1; evaluates to a value before decrementing op Decrements op by 1; evaluates to a value after decrementing

5 Increment or Decrement Operators Example : 1. What is the value of j and i after executing the following code? i = 1; j = 5; j = ++i; 2. What is the value of j and i after executing the following code? i = 10; j = 50; j = i--; 3. What is the value of j and i after executing the following code? i = 5; j = 10; i++; ++j;

6 Short Hand Operators Java also provides a number of operators that can be used as a short-cut for performing arithmetic operations on a variable and assigning the result to the same variable. Operator Short-FormEquivalent to += op1 += op2 op1 = op1 + op2 -= op1 -= op2 op1 = op1 - op2 *= op1 *= op2 op1 = op1 * op2 /= op1 /= op2 op1 = op1 / op2 %= op1 %= op2 op1 = op1 % op2 Example : Instead of writing a = a + 5 We can write a += 5 If the variable name on both sides of assignment operator are same then bring the operator, before the = operator. a = a + 5

7 The Math class l Java provides a number of mathematical function as static methods in the Math class. E The best approximate value of e, the base of the natural log PI The best approximate value of  abs (a) Returns the absolute value of a, a can be double, float, int or long. cos (a) sin (a) tan (a) Returns the trigonometric cosine/sine/tangent of an angle in radians exp (a) Returns the exponential number e raised to the power of a log (a) Returns the natural logarithm (base e) of a max (a, b) min (a, b) Returns the greater/smaller of two values, a and b can double, float, int or long pow (a, b) Returns value of the first argument raised to the power of the second random () Returns a random value in the range 0.0 and 1.0 round (a) Returns the closest long to the argument, the argument can be double or float toDegrees(a) toRadians(a) Converts an angle in radians to the degrees Converts an angle in degrees to the radians

8 Evaluating Arithmetic Expression With Simple Math functions - Example class Expressions { public static void main(String[]args) { double area, circumference; int radius=3; area = Math.PI * Math.pow(radius, 2); circumference = 2 * Math.PI * radius; System.out.println("Area = " + area); System.out.println("Circum. =" + circumference); }

9 Casting We learnt earlier that the following division 5 / 2 results in 2 Because the / operator is operating between 2 integer type constants, the result will be an integer. To get 2.5, we need to convert either 1 or both the operands to double. Then the division will look like 5.0 / 2.0 But what if we have integer variables to divide each other, like a / b ? For this, cast operator is used. (double) a / (double) b

10 Casting (Cont’d) Conversion of primitives is accomplished by (1) assignment and/or (2) explicit casting: int total = 100; float temp = total; // temp now holds When changing type that will result in a loss of precision, an explicit ‘cast’ is needed. This is done by placing the new type in parenthesis: float total = 100F; int temp = total; // ERROR! int start = (int) total;