Scjp 310-055 (Declaration And Access Control)

Front 1

Given:

class A {}
class B {}

Define access in terms of class B to class A

Back 1

Code from class B can instantiate an object of class A. Class B can extend class A.

Front 2

What two access modifiers can be used with class definitions?

Back 2

public
default (no modifier)

Front 3

Define default access regarding classes

Back 3

Code only accessible to classes in the same package

Front 4

Define public access regarding classes

Back 4

Code is accessible to any class in the same package and must be imported to classes in separate packages

Front 5

Given:

// A.java
package pack1;
class A {}

// B.java
package pack1;
class B {};

Name the type of access that exists between these two classes

Back 5

Default

Front 6

Will the following code segment compile? Why or why not?

//A.java
package pk1;
class A {

}

//B.java
package pk2;
import pk1.A;
class B extends A {

}

Back 6

No. Class has default access only to classes in the same package and class B is in a completely different package.

Front 7

Will the following compile? Why or Why not?

//A.java
package pk1;
public class A {

}

//B.java
package pk2;
import pk1.A;
class B extends A {

}

Back 7

Yes. Class A has public access and class B has imported public class A.

Front 8

What are 5 characteristics of Abstract classes?

Back 8

1: Can't be instantiated and must be sub-classed
2: abstract methods must be marked public abstract
3: can have fully implemented methods
4: can declare instance variables
5: The first concrete subclass must implement all abstract methods or be marked abstract.

Front 9

How many abstract methods are required to consider a class abstract?

Back 9

One.

Front 10

What are nine characteristics of interfaces?

Back 10

1: a 100% abstract class
2: can only have abstract methods
3: implicitly abstract
4: can extend other interfaces
5: methods are implicitly public abstract
6: all methods must be fully implemented or class should be marked abstract
7: instance variables are implicitly public static final and can't be modified
8: methods can't be static, final, protected, private
9: can be used polymorphically (Interface type)

Front 11

What does strictfp mean when applied to a class?


public strictfp class A {

}

Back 11

The class has methods which conform to IEEE 754 standards for floating point operations.

Front 12

What is a characteristic of a class marked final?

public final class A {

}

Back 12

Final classes can't be subclassed.

Front 13

Given:

class A {}
class B {}

Define member access in terms of class B to class A

Back 13

Code in class B can instantiate objects of class A. Code in class B can invoke methods on objects of class A. Code in class B can inherit a member of class A.

Front 14

Define public member access.

Back 14

Assuming the class is visible via public or default access, all other classes can access this method or variable and methods of this type can be overriden via inheritance.

Front 15

Define private member access.

Back 15

Assuming the class is visible, private members can only be accessed in the class where they are declared and are not inherited by the subclasses. private methods cannot be overriden

Front 16

Define default member access.

Back 16

members can only be accessed only by a class in the same package.
are not inherited by subclasses in diff packages

Front 17

Defiine protected member access.

Back 17

members can only be accessed only by a class in the same
package. can be accessed by inherited subclasses in diff packages

Front 18

When a class's method is marked final, what does that mean?

Back 18

It is a method that can't be overriden

Front 19

When a method has an argument marked final, what does that mean?

Back 19

Final method arguments can't be modified.

Front 20

What is a synchronized method?

Back 20

A method that can accessed by only 1 thread at a time.

Front 21

What is a strictfp method?

Back 21

A a method that conforms to the IEEE 754 standard for floating point operations.

Front 22

Write method named m1. Should have with default access, no return type, and a variable argument list of type class A

Back 22

void m1(A... a) {

}

Front 23

What the three characteristics regarding methods with variable argument lists?

Back 23

The var args must be last parameter in the method.
Can only have one per method signature.
Can have other parameters in the method signature.

Front 24

What are five characteristics of constructors?

Back 24

No return type
Can use access modifiers
Can take arguments and var args
Must have same name as the class
Can't be static, final, or abstract

Front 25

Name the 7 Java primatives

Back 25

char
boolean
byte
short
int
long
double
float

Front 26

declare an array of ints

Back 26

int[] variableName;

Front 27

What type of variable must be initialized and can't be changed?

Back 27

A final variable

Front 28

What is a static variable?

Back 28

One copy for the entire class

Front 29

Given

enum TestEnum {ONE, TWO, THREE}
class A {

TestEnum te;
}

public class Test1 {
public static void main(String[] args) {

A a = new A();
a.te = FILL IN THE BLANK;
}
}

Back 29

a.te = TestEnum.ONE;

the enum is defined outside of the class can be referenced with the enum's name

Front 30

Given

class A {

TestEnum te;
enum TestEnum {ONE, TWO, THREE};
}

public class Test1 {
public static void main(String[] args) {

A a = new A();
a.te = FILL IN THE BLANK;
}
}

Back 30

a.te = A.TestEnum.ONE;

Front 31

What are 4 characteristics of enum's?

Back 31

Can't invoke enum constructor directly
Can't declare enum in a method
enum constructor can have none or many values
can be declared in their own class or enclosed in another class

Front 32

What three characters can an identifiers begin with?

Back 32

letter
underscore
currency symbol

Front 33

When can identifier names includes digits?

Back 33

After the first character

Front 34

What are the javabeans method naming rules

Back 34

camelCasing
set
get
is
add
remove

Front 35

How many public classes can appear in a single source file?

Back 35

One

Front 36

If a source file has a public class, what should the file name be?

Back 36

Same as the public class name.

Front 37

How many package statements can a source file have?

Back 37

One

Front 38

Where do import statements go?

Back 38

After the package statement if there is one they should be the first no comment in a source file

Front 39

How many non public classes can a source file have?

Back 39

one or more

Front 40

If a source file has no public class, what should it's filename be?

Back 40

What ever you like.

Front 41

What are the three access modifiers?

Back 41

public
protected
private

Front 42

What are the four levels of access?

Back 42

default
public
private
protected

Front 43

What type of access can classes have?

Back 43

public or default

Front 44

A class with default access can be seen by...

Back 44

only classes in the same package

Front 45

A class with public access can be seen by...

Back 45

All classes from all packages

Front 46

Class visibility revolves around whether code in one class can...

Back 46

Create an instance of another class
Extend another class
Access methods and variables of another class

Front 47

What are the three non access modifiers that can be used for classes?

Back 47

final
abstract
strictfp

Front 48

Can a class be both final and abstract?

Back 48

No

Front 49

Can an abstract class be instantiated?

Back 49

no

Front 50

Can an interface have concrete methods?

Back 50

no

Front 51

Interface methods have what implicit modifiers?

Back 51

public abstract

Front 52

Interface constants have what implicit modifiers?

Back 52

public static final