001 - Hello World App

Question 1

Question 2: Which of the following is not a valid comment:

a. /** comment /
b. / comment /
c. / comment
d. // comment

Answer 1

c. /* comment

Question 2

Question 3: What is the first thing you should check if you see the following error at runtime:

Exception in thread “main” java.lang.NoClassDefFoundError:
HelloWorldApp.java.

Answer 2

Answer 3: Check your classpath. Your class cannot be found.

Question 3

Question 4: What is the correct signature of the main method?

Answer 3

Answer 4: The correct signature is public static void main(String[] args) or public static void main(String… args)

Question 4

Question 5: When declaring the main method, which modifier must come first, public or static?

Answer 4

Answer 5: They can be in either order, but the convention is public static.

Question 5

Question 6: What parameters does the main method define?

Answer 5

Answer 6: The main method defines a single parameter, usually named args, whose type is an array of String objects.

Question 6

Exercise 1: Change the HelloWorldApp.java program so that it displays Hola Mundo! instead of Hello World!.

Answer 6

Answer 1: This is the only line of code that must change:

System.out.println(“Hola Mundo!”); //Display the string.

Question 7

Exercise 2: You can find a slightly modified version of HelloWorldApp here: HelloWorldApp2.java

The program has an error. Fix the error so that the program successfully compiles and runs. What was the error?

Answer 7

Answer 2: Here’s the error you get when you try to compile the program:

HelloWorldApp2.java:7: unclosed string literal
System.out.println(“Hello World!); //Display the string.
^
HelloWorldApp2.java:7: ‘)’ expected
System.out.println(“Hello World!); //Display the string.

Question 8

Question 1: When you compile a program written in the Java programming language, the compiler converts the human-readable source file into platform-independent code that a Java Virtual Machine can understand. What is this platform-independent code called?

Answer 8

Bytecode

Question 9

When creating a new Hello World app In the Name and Location page of the Netbeans new project wizard:

In the Project Name field, type ________
In the Create Main Class field, type _________.

Answer 9

Hello World App.

helloworldapp.HelloWorldApp

Question 10

When you build the project, the __________ file HelloWorldApp.class is generated.

Answer 10

bytecode

Question 11

You can compile an individual file (as opposed to a whole project) using the IDE’s ________ (_________) command.

Answer 11

Compile File

F9

Question 12

You can run an individual file (as opposed to a whole project) using the IDE’s __________ (___________) command.

Answer 12

Run Fille

Shift-F6

Question 13

To turn off or on the

Auto Popup Completion Window

Answer 13

Choose 
Tools | 
     Options | 
          Editor, 
click the 
     Code Completion tab 
and clear the 
     Auto Popup Completion Window checkbox.

Question 14

When creating a new Java program in Windows notepad, in the Encoding combo box, the encoding must be left as _________.

Answer 14

ANSI

Question 15

To compile a HelloWorld app in CMD. At the prompt, type _________ command and press Enter.

Answer 15

javac HelloWorldApp.java

Question 16

To run the Hello World Program with CMD:

In the same directory, enter the following command at the prompt:

Answer 16

java -cp . HelloWorldApp