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Introduction to Programming Java Lab 8: Methods 1 March 2013 1 JavaLab8 lecture slides.ppt Ping Brennan

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Presentation on theme: "Introduction to Programming Java Lab 8: Methods 1 March 2013 1 JavaLab8 lecture slides.ppt Ping Brennan"— Presentation transcript:

1 Introduction to Programming Java Lab 8: Methods 1 March JavaLab8 lecture slides.ppt Ping Brennan

2 Java Project Project Name: JavaLab8 2 RepeatString ReadDouble

3 Method Declaration for cubeVolume (in JFE, part 5.2) 3 public static double cubeVolume (double sideLength) { double volume = sideLength * sideLength * sideLength; return volume; } Type of return value Method name Type of parameter variable Name of parameter variable Passing a parameter return statement exits method and returns volume. Method body, executed when method is called.

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. 4

5 Class RepeatString Method public static String repeat (String str, int n) 5 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

6 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 6 Method name Call to method repeat

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

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. 8

9 Class ReadDouble Method public static double readDouble(String prompt) Usage in method main double salary = readDouble("Please enter your salary: " ); // read in salary 9 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, // , and returns it. Computations Inside method readDouble: double inSalary = in.nextDouble(); return inSalary; Prompt Please enter your salary: (users input in red) Output The entered salary is

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 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 10

11 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 11


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