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Trail: Getting Started

Questions and Exercises: Getting Started

Questions

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?

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

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

3: What is the first thing you should check if at runtime you see the following error: Exception in thread "main" java.lang.NoClassDefFoundError: HelloWorldApp.java.

Exercises

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

2: Download this file: Useless.java Compile and run this program. What is the output?

3: 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?

4: Download the following two source files:

• FirstClass.java
• SecondClass.java

Compile the files, and then run the resulting program. What is the output? If you have trouble compiling the files but have successfully compiled before, try unsetting the CLASSPATH environment variable, and then compile again.

Check your answers.

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