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

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 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.

4. 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.

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 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
Method name
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 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.

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 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,
// , and returns it.
Computations
Inside method readDouble:
double inSalary = in.nextDouble();
return inSalary;
Prompt
Please enter your salary: (user’s 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

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