1b	Advanced Placement Computer Science Lab

Programming Errors

Introduction

In this lab we will write some simple Java programs and explore the different types of errors that you will encounter as you develop and write programs. The three types of errors that are typically encountered in writing programs are the following:

· compile time errors

· runtime errors

· logical errors

Compile time errors occur when you are attempting to compile your program and the IDE reports an error. It will usually give the line number at which the error occurred. An example would be a failure to put a semicolon at the end of a statement. A runtime error occurs while you are executing your program. A typical runtime error would be division by zero. A logical error is when your program executes, but fails to produce the desired result. Sometimes the errors of each type can be difficult to correct, but often time the logical errors are the most difficult because they are the hardest to see.

Procedure

Create a New Project and Test Errors of Different Types

1. As in the previous exercise, create a new project labeled "ErrorTest".

2. Create a new class in the project as in the previous exercise.

3. Copy the following code and use it to replace the code that the IDE gives

/*

ErrorTest.java

(Your Name) Version (x.x) (date xx/xx/xx)

Program places several strings on screen

*/

class ErrorTest

{

public static void main (String args[])

{

System.out.println("Now is the time");

System.out.println("for all good men to");

System.out.println("come to the aid of");

System.out.println("their country.");

}//end main

}//end class

4. Compile and execute the code.

5. Change the name of the class to "ErrTest" and compile and run. What happens? If there is an error what type of error is it?

6. Delete the semicolon from the line ' System.out.println("Now is the time");'. and compile and run. What happens? If there is an error what type of error is it?

7. Change the spelling of one of the words in the line ' System.out.println("for all good men to");' and compile and run. What happens? If there is an error what type of error is it?

8. Delete one of the quotation marks in the line ' System.out.println("come to the aid of");' and compile and run. What happens? If there is an error what type of error is it?

9. Change "println" to "print" in the line ' System.out.println("come to the aid of");' and compile and run. What happens? If there is an error what type of error is it?

10. Change "static" to "Static" in the line ' public static void main (String args[])' and compile and run. What happens? If there is an error what type of error is it?

10. Add a semicolon after the line ' public static void main (String args[])' and compile and run. What happens? If there is an error what type of error is it?

Programming Assignment

1. Write a program to print the poem of your choice on the screen. (it must not be the same as your neighbors!)

2. Turn in a program listing your source code as with the first exercise. Be sure to modify the output window properties to change the background and foreground colors.

Questions

1. What is the function of having a "main" method?.

2. What do you think the function of the "(String[] args)" is?.

3. What is the difference between RAM and ROM?

4. How do you suppose that you might get the computer to print quotation marks on the screen?

5. What are the reserved words in the above listing?