Introduction to Programming Java Lab 8: Methods JavaLab8 lecture slides.ppt Ping Brennan (p.brennan@dcs.bbk.ac.uk) 1 March 2013

Java Project Project Name: JavaLab8 RepeatString ReadDouble

Method Declaration for cubeVolume (in JFE, part 5.2) Passing a parameter Type of return value Type of parameter variable Method name Name of parameter variable public static double cubeVolume(double sideLength) { double volume = sideLength * sideLength * sideLength; return volume; } Method body, executed when method is called. return statement exits method and returns volume.

Class RepeatString Class RepeatString contains two methods: Objectives First method is the usual one, main Second method repeat returns the string str repeated n times. (See JFE, P5.5) Objectives Understand how to pass and return values in methods. Using methods to solve problems.

Class RepeatString Method public static String repeat(String str, int n) Input int n = 3; // first example int n = 1; // second example Examples (in main): String str1 = repeat("ho", 3); String str2 = repeat("ho", 1); Loop for statement Print str1 repeated 3 times. Print str2 repeated 1 time. Output hohoho ho

Anatomy of Class RepeatString import java.util.Scanner; public class RepeatString { public static void main(String[] args) String str1 = repeat("ho", 3); System.out.println("First example: " + str1); /* To do: write more code to make a number of calls to the method repeat */ } // end of main /* To do: insert code for the method repeat here (which is shown on next slide) */ } // end of class RepeatString Method name Call to method repeat

Method Declaration for repeat Passing a parameter Type of return value Type of parameter variable Method name Name of parameter variable public static String repeat(String str, int n) { String result = ""; /* To do: write a for statement to loop n times, each time joining the string, str, to current value in result. */ return result; } Method body, executed when method is called. return statement exits method and returns result.

Class ReadDouble Displays a prompt string, followed by a space, and then reads in a number of type double. Objective Construct a method to return a floating point number after reading it inside the method when prompted.

Class ReadDouble Method public static double readDouble(String prompt) Usage in method main double salary = readDouble("Please enter your salary: " ); // read in salary Input A prompt string. double salary; Example (in main): salary = readDouble("Please enter your salary: "); // Method displays prompt, then // reads in a floating point number, // 31000.50, and returns it. Computations Inside method readDouble: double inSalary = in.nextDouble(); return inSalary; Prompt Please enter your salary: 31000.50 (user’s input in red) Output The entered salary is 31000.50

Anatomy of Class ReadDouble import java.util.Scanner; public class ReadDouble { public static void main(String[] args) double salary = readDouble("Please enter your salary: "); /* To do: write code to print out the salary */ /* To do: include a number of calls to the method readDouble, and print the results */ } // end of main /* To do: insert code for the method readDouble here (which is shown on next slide) */ } // end of class ReadDouble

Method declaration for readDouble public static double readDouble(String prompt) { Scanner in = new Scanner(System.in); System.out.print(prompt + " "); /* To do: write code to declare a variable, inSalary, of type double, and assign it the keyboard input. Hint: use in.nextDouble() to read in a value. */ /* To do: lastly write code to return inSalary */ } // end of readDouble