Chapter 1

Question 1

Constructors

Answer 1

There are two key points to note about the constructor: the name of the constructor matches the name of the class, and there’s no return type.

Question 2

The rules for what a Java code file contains

Answer 2

■ Each file can contain only one class.

■ The filename must match the class name, including case, and have a .java extension.

Question 3

A value is assigned to a reference in one of two ways:

Answer 3

■ A reference can be assigned to another object of the same type.

■ A reference can be assigned to a new object using the new keyword.

Question 4

important differences you should know between primitives and reference types.

Answer 4

First, reference types can be assigned null, which means they do not currently refer to an object. Primitive types will give you a compiler error if you attempt to assign them null.

Next, reference types can be used to call methods when they do not point to null. Primitives do not have methods declared on them. Primitives do not have methods.

Finally, notice that all the primitive types have lowercase type names. All classes that come with Java begin with uppercase.

Question 5

Three rules to remember for legal identifiers:

Answer 5

• The name must begin with a letter or the symbol $ or _.
• Subsequent characters may also be numbers.
• You cannot use the same name as a Java reserved word

Question 6

Rule for instance variables

Answer 6

they are available as soon as they are defined and last for the entire lifetime of the object itself.

Question 7

The rule for class (static) variables

Answer 7

they go into scope when declared like the other variables types. However, they stay in scope for the entire life of the program.

Question 8

The rules on scope: (Local, instance, and class variables)

Answer 8

Local variables—in scope from declaration to end of block

Instance variables—in scope from declaration until object garbage collected

Class variables—in scope from declaration until program ends

Question 9

PIC

Answer 9

Package declaration- Required? - No
Import statements - Required? - No
Class declaration - Required? - YES

Question 10

_______ ________ can be defined in the same file, but only ___ of them is allowed to be public

Answer 10

• multiple classes
• one

Question 11

A file is also allowed to have _______ class be public. As long as there isn’t more than ___ public class in a file, it is okay.

Answer 11

• neither
• one

Question 12

System.gc()

Answer 12

Is not guaranteed to run, and you should be able to recognize when objects become eligible for garbage collection.

Question 13

An object is no longer reachable when one of two situations occurs

Answer 13

• The object no longer has any references pointing to it.
• All references to the object have gone out of scope.

Question 14

finalize()

Answer 14

Could run zero or one time.

Question 15

Benefits of Java

Answer 15

• Object Oriented
• Encapsulation
• Platform Independent
• Robust
• Simple
• Secure