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Answers to Questions and Exercises: Getting Started

> ### Questions

> > 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 1: Bytecode.

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

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

> > Answer 2: c is an invalid comment.

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

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

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

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

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

> > Question 6: What parameters does the `main` method define?

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

> ### Exercises

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

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

> > >     System.out.println("Hola Mundo!"); //Display the string.

> > 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 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.
> > >                                                                     ^
> > >     2 errors

> > To fix this mistake, you need to close the quotation marks around the string. Here is the correct line of code:

> > >      System.out.println("Hello World!"); //Display the string.

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