Introduction to Programming

1. Introduction to Programming Java Lab 8: Methods JavaLab8 lecture slides.ppt Ping Brennan (Ping.Brennan@gmail.com) 28 February 2014

2. Java Project Project Name: JavaLab8 RepeatString ReadDouble

3. 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 doublecubeVolume(doublesideLength) { double volume = sideLength* sideLength* sideLength; returnvolume; } Method body, executed when method is called. return statement exits method and returns volume.

4. Class RepeatString • Class RepeatString contains two methods: • 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.

5. Class RepeatString • Method public static String repeat(String str, int n) Input int n = 3; // first example int n = 1; // second example Examples (in method 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

6. Anatomy of Class RepeatString Method name import java.util.Scanner; public class RepeatString { publicstaticvoidmain(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 slide 7) */ } // end of class RepeatString Call to method repeat

7. Method Declaration for repeat Passing a parameter Type of return value Type of parameter variable Method name Name of parameter variable public static Stringrepeat(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. */ returnresult; } Method body, executed when method is called. return statement exits method and returns result.

8. 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.

9. Class ReadDouble • Method public staticdoublereadDouble(String prompt) • Usage in method main double salary = readDouble("Please enter your salary: " ); // read in salary Input A prompt string. double salary; Example (in method 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 green) Output The entered salary is 31000.50

10. 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 the code to print out the salary */ /* To Do: write more code to 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 slide 11) */ } // end of class ReadDouble

11. Method declaration for readDouble public static doublereadDouble(String prompt) { Scanner in = new Scanner(System.in); System.out.print(prompt + " "); /* To Do: write more 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: lastlywrite more code to return inSalary*/ } // end of readDouble