chapter 1

Question 1

What are 8 benefits of Java?

Answer 1

1. Object Oriented
2. Encapsulation
3. Platform Independent
4. Robust
5. Simple
6. Secure
7. Multithreaded
8. Backward Compatibility

Question 2

What are the the basic building blocks in java programs?

Answer 2

classes

Question 3

What is an oject?

Answer 3

A runtime instance of a class in memory.

Question 4

What is a reference?

Answer 4

A variable that points to an object.

Question 5

What are the two primary elements of a class in Java?

Answer 5

methods and fields (variables).

Question 6

What makes up a method signature?

Answer 6

method name and parameter types.

Question 7

What makes up a method declaration?

Answer 7

method name, parameter types, and return type.

Question 8

Describe three different types of comments in java.

Answer 8

single line comment
// comment 
multi line comments
/**/
or
/**
 * Java Doc comment
 */

Question 9

Where does a Java program begin execution?

Answer 9

the main()

Question 10

What must a file have to compile Java code?

Answer 10

A .java file extension and a filename that matches the class name.

Question 11

What is the result of compiling a .java file?

Answer 11

A file of bytecode by the same name but with a .class extension.

Question 12

How many public classes are allowed in a file?

Answer 12

one.

Question 13

What is the syntax for the single-file source-code-command?

Answer 13

java HelloWorld.java

Question 14

What is the single-file source-code-command

Answer 14

Command to run java programs that exist in a single file.

Question 15

Does the single-file source-code-command produce a .class file?

Answer 15

No, the program is contained in memory.

Question 16

What are the constraints placed on programs run with the single-file source-code-command?

Answer 16

They are for programs with only one class.

Can only import code that came with the JDK.

Question 17

What are packages?

Answer 17

Logical groupings of classes.

Question 18

What do import statements do?

Answer 18

Tell java which package to look in for a class.

Question 19

How do you know a package comes from the JDK?

Answer 19

The package name starts with java or javax.

Question 20

What is the “*” in the context of importing packages in Java?

Answer 20

A wildcard that matches all classes in a package.

Question 21

What is the one package that is automatically imported in Java?

Answer 21

java.lang.

Question 22

Is it required to import a class that is in the same package?

Answer 22

No, Java automatically looks in the current package for other classes.

Question 23

How do you resolve two package imports with wildcards where there are class name conflicts? (e.g. Date class)

Answer 23

Explicitly import one class name, it takes precedence over any wildcards present.
import java.util.Date;
import java.sql.*;

Question 24

How can you use two classes with the same name in Java?

Answer 24

Use the fully qualified class name.
public class foo {
java.util.Date date;
java.sql.Date sqlDate;
}

Question 25

What option is used with the javac command to specify the directory to place generated class files?

Answer 25

• d

e. g. javac -d classes foo/Bar.java

Question 26

What are the options to specify the class path when running the java command?

Answer 26

-cp
-classpath
–class-path
Location of classes needed to compile a program.

Question 27

What does the jar command do?

Answer 27

Creates an archive for classes and resources, and can manipulate or restore individual classes or resources from an archive.

Question 28

What is the command to create a jar file?

Answer 28

jar - jarName.jar currentDir

Question 29

what does the -c, –create option with the jar command do?

Answer 29

Creates a new JAR file.

Question 30

What does the -v, –verbose option with the jar command do?

Answer 30

Prints details when working with JAR files.

Question 31

What does the -f , –file option with the jar command do?

Answer 31

Provides the jar name.

Question 32

What does the -C option with the jar command do?

Answer 32

Provides the directory containing files to be used to create the JAR.

Question 33

Is a package declaration required in a class file?

Answer 33

No.

Question 34

Are import statements required in a class file?

Answer 34

No.

Question 35

Is a class declaration required in a class file?

Answer 35

Yes.

Question 36

Are field declarations required in a class file?

Answer 36

No.

Question 37

Are method declarations required in a class file?

Answer 37

No.

Question 38

Where does a package declaration go in a class file?

Answer 38

First line in the file.

Question 39

Where do import statements go in a class file?

Answer 39

Immediately after the package (if present).

Question 40

Where does the class declaration go in a class file?

Answer 40

Immediately after the import statements (if any).

Question 41

Where do field declarations go in a class file?

Answer 41

Any top level element in a class.

Question 42

Where do method declarations go in a class file?

Answer 42

Any top level element in a class.

Question 43

What must the public class name in a file match?

Answer 43

The name of the file.

Question 44

How many classes can be defined in a file?

Answer 44

multiple.

Question 45

During the OCM exams, what are common cases where you don’t need to check for imports?

Answer 45

1. Code that begins with a class name.
2. Code that begins with a method declaration.
3. Code snippets that would normally be inside a class or method.
4. Code that has line numbers that don’t begin with 1.

Question 46

What does JDK stand for?

Answer 46

Java Devlopment Kit.

Question 47

What does the JDK contain?

Answer 47

The compiler and JVM launcher.

Question 48

What does JVM stand for?

Answer 48

Java Virtual Machine.

Question 49

What does the JVM run?

Answer 49

bytecode.