Java Programming Itis 1213 Gaddis Test2

Front 1

Assume a class BankAccount has been created, and the following statement correctly creates an instance of the class:

BankAccount account = new BankAccount(5000.0);

What is true about the following statement?
System.out.print(account);

Back 1

the account object's toString method will be called.

Front 2

Giving the following Java statement, which statement will write"Eagle" to the file DiskFile.txt?
PrintWriter diskOut = new PreintWriter("DiskFile.txt");

Back 2

diskOut.println("Eagle");

Front 3

When using the DecimalFormat class, which of the following will .1359 to 013.6%?

Back 3

000.0%

Front 4

What will be returned from a method, if the following is the method header?

public Rectangle getRectangle()

Back 4

the address of an object of the Rectangle class

Front 5

To compare two objects in a java class you must____.

Back 5

write an equals method that will make a field comparison of the two objects.

Front 6

What will generate a random number from 0 -1.0?

Random rand = new Random();

Back 6

System.out.print(rand.nextDouble());

Front 7

What is the import statement for PrintWriter?

Back 7

import java.io.*;

Front 8

What will the following output return?

Scanner keyboard = new Scanner(System.in);

String filename;

System.out.print("Enter the filename: ");

filename = keyboard.readString();

PrintWriter outFile = new PrintWriter(filename);

Back 8

Nothing. There is a syntax error.

Front 9

You have a defined a class CheckingAccount with a public static field named account and created a CheckingAccount object referenced by the variable, bankAccount. Which of the following will reference the account?

Back 9

CheckingAccount.account;

Front 10

What will open a file named MyFile.txt and allow you to read data from it?

Back 10

File fileName = new File("MyFile");

Scanner inputFile = new Scanner(fileName);

Front 11

How is an object created from a class?

Back 11

import java.util.Random;

Random randomNumbers= new Random();

Front 12

Methods of the Random Class

Back 12

nextInt(int n) - T

Front 13

Use three useful methods from the math class?

Back 13

Math.pow();

Math.sqrt();

Math.PI

Math.rnd();

Front 14

What does the JOptionPane class do?

Back 14

Allows you to display a message or input

Front 15

• Give the method for the JOptionPane to display output?

Give an example?

Back 15

JOptionPane.showMessageDialog

JOptionPane.showMessageDialog(null, “Hello World”);

Front 16

Parse Methods

Back 16

// Store 2599 in iVar.
Int iVar = Integer.parseInt(“2599”);

Front 17

DecimalFormat class
What does the # sign mean?

Back 17

suppresses zeros

Front 18

What does the zero mean in that format?
i

Back 18

t means that is will display the position but if the # sign is there it will suppress the decimal.

Front 19

What’s the difference between an input file and an output file

Back 19

Input a file in which you would input data…read data
Output a file into which you would write a file from your data.

Front 20

What’s the import statement that you need in an file operation?

Back 20

import java.io*;

Front 21

static fields and static methods are also known as _____.

Back 21

Class fields or class methods.

Front 22

To invoke a static method or use a static field, ______, rather than the object name, is used.

Back 22

the class name

Front 23

When a class contains a static method, it is not necessary to create an ________.

Back 23

instance of the class in order to use the method

Front 24

static methods may not communicate with instance fields, only_______.

Back 24

static fields

Front 25

Normally, each object has its own data space, but if a variable is declared as static, only ______ of the variable exists
private static int count;

Back 25

one copy

Front 26

An object reference variable that does not currently point to an object is called a________.

Back 26

null reference

Front 27

The reserved word null can be used to explicitly set a null reference:

Back 27

name = null;

or

if (name == null)
System.out.println("Invalid");

Front 28

The _____ reference is simply a name that an object can use to refer to itself.

Back 28

this

Front 29

The _______ reference can be used to allow a parameter to have the same name as an instance field.

public void setLength(double length)
{
this.length = length;
}

Back 29

this

Front 30

The _______ method of a class can be called explicitly: (distance is an object of the FeetInches class)

Back 30

toString()

Front 31

an example of String method being used:

Back 31

System.out.println("The distance you entered is "
+ distance.toString());

Front 32

An example of the the toString() method does not have to be called explicitly but is called implicitly whenever you concatenate an object of the class with a string:

Back 32

System.out.println("The distance you entered is "
+ distance);

Front 33

All objects have a toString() method that returns______ & ______ of the object.

Back 33

the class name

a hash of the memory address

Front 34

When objects are no longer needed they should be _____.

Back 34

destroyed

Front 35

The _______ will reclaim memory from any object that no longer has a valid reference pointing to it.

Back 35

garbage collector

Front 36

Instead of using the == operator to compare two objects, we should use the _____.

Back 36

equals method

Front 37

The equals method will compare objects by their _______ rather than by their memory addresses.

Back 37

contents

Front 38

Java uses the method signature (name, type of parameters and order of parameters) to determine which method to call?

Back 38

Overloaded method

Front 39

Operations performed by the I/O classes may throw an _______.

Back 39

IOException

Front 40

An example of throws IOException:

Back 40

public static void main (String[] args) throws IOException

Front 41

input file name is stored in variable file

Back 41

String line, file = "inventory.txt";

File openFile = new File (file);
Scanner inFile = new Scanner (openFile);

Front 42

The _____ class is used to open the input file.

Back 42

File

nextLine method is from Scanner class

Front 43

When reading text tiles, an example that reads reads one line of text file as String data and stores it in the variable line:

Back 43

line = inFile.nextLine();

Front 44

_________________ creates a loop which will iterate until all the lines of the file are read:

Back 44

while (inFile.hasNext())

Front 45

An example of closing a file:

Back 45

inFile.close();