TOPIC 6 Methods F Introducing Methods F Declaring Methods F Calling Methods F Passing Parameters F Pass by Value F Overloading Methods F Method Abstraction  The Math Class

Creating A Method

Declaring Methods public static int max(int num1, int num2) { if (num1 > num2) return num1; else return num2; }

Calling Methods F Two ways to call/invoke: (1)Method returns a value - call to method usually treated as a value - e.g. int larger = max(3, 4); System.out.println(max(3, 4)); (2)Method returns void - call to method must be a statement - e.g. System.out.println(“Welcome”);

Calling Methods F How is control passed back to the calling method?

public class TestMax { public static void main(String [ ] args) { int i = 5; int j = 2; int k = max(i, j); System.out.println(“Maximum between “ + i + “ and “ + j + “ is “ + k); } public static int max(int num1, int num2) { if (num1 > num2) return num1; else return num2; }

Passing Parameters F Formal parameters F Actual parameters F Parameter order association –Actual parameters must match the formal parameters in type, order and number. F Pass by Value -Copy of the value of the actual parameter is passed to the method. -Actual value of parameter outside method is not affected, regardless of any changes made to the formal parameter inside the method.

Overloading Methods double max(double num1, double num2) { if (num1 > num2) return num1; else return num2; }  Methods have the same name i.e. max, but different parameters. F Method signature –Method name with the parameter profiles. –Java runtime system determines which method to used based on the message signature.

The Math Class F Class constants: –PI –E F Class methods: –Trigonometric Methods –Exponent Methods –Miscellaneous

Exponent Methods  exp(double a) Returns e raised to the power of a.  log(double a) Returns the natural logarithm of a.  pow(double a, double b) Returns a raised to the power of b.  sqrt(double a) Returns the square root of a.

Miscellaneous Methods  max(a, b) and min(a, b) Returns the maximum or minimum of two parameters.  abs(a) Returns the absolute value of the parameter.  random() Returns a random double value in the range [0.0, 1.0).