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This program is the same as the program in Question 4 with a major exception. Specifically, the program contains the import directive shown in the following fragment.

import java.util.ArrayList;

A shortcut

The designers of Java recognized that having to type a fully-qualified name for every reference to a class in a Java program can become burdensome.Therefore, they provided us with a shortcut that can be used, so long as we don't need to refer to two or more class files having the same name.

Import directives

The shortcut is called an import directive.

As can be seen above, the import directive consists of the word import followed by the fully-qualified name of a class file that will be used in theprogram.

A program may have more than one import directive, with each import directive specifying the location of a different class file.

The import directive(s) must appear before any class or interface definitions in the source code.

The alternative wild-card syntax

An alternative form of the import directive replaces the name of the class with an asterisk.

The asterisk behaves as a wild-card character. It tells the compiler to use any class file that it finds in that package that matches a class reference inthe source code.

The wild-card form should be used with care, because it can sometimes cause the compiler to use a class file that is different from the one that youintended to use (if it finds the wrong one first) .

Class file name collisions

If your source code refers to two different class files having the same name, you must forego the use of the import directive and provide fully-qualifiednames for those class files.

Back to Question 5

Answer 4

A. Compiler Error

Explanation 4

The purpose of this program is to continue to illustrate the use of java packages.

No fully-qualified class names

This program is the same as the program in Question 3 with a major exception. Neither of the references to the ArrayList class use fully-qualified names in this program. Rather, the references are as shown in the following fragment.

ArrayList ref = new ArrayList(1);

Compiler errors

As a result, the JDK 1.3 compiler produces two error messages similar to the following:

Ap144.java:20: cannot resolve symbol symbol : class ArrayListlocation: class Worker ArrayList ref =

Doesn't know how to find the class file

This error message indicates that the compiler didn't know where to look on the disk to find the file named ArrayList.class

Back to Question 4

Answer 3

C. ABC DEF GHI

Explanation 3

Illustrate the use of java packages

Since it was necessary to make use of a class to illustrate packages, this program also previews the use of the ArrayList class. We will be very interested in this class later when we study Java data containers.

What is an ArrayList object?

Some of this terminology may not make much sense to you at this point, but I'll go ahead and tell you anyway, just as a preview.

According to Sun, the ArrayList class provides a

"Resizable-array implementation of the List interface. Implements all optional list operations, and permits all elements, including null. Inaddition to implementing the List interface, this class provides methods to manipulate the size of the array that is used internally to store the list.(This class is roughly equivalent to Vector , except that it is unsynchronized.)"

Questions & Answers

A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
Aislinn Reply
cm
tijani
what is titration
John Reply
what is physics
Siyaka Reply
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Jude Reply
Can you compute that for me. Ty
Jude
what is the dimension formula of energy?
David Reply
what is viscosity?
David
what is inorganic
emma Reply
what is chemistry
Youesf Reply
what is inorganic
emma
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
Krampah Reply
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
Sahid Reply
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
Samuel Reply
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Joseph Reply
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
Ryan
what's motion
Maurice Reply
what are the types of wave
Maurice
answer
Magreth
progressive wave
Magreth
hello friend how are you
Muhammad Reply
fine, how about you?
Mohammed
hi
Mujahid
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
yasuo Reply
Who can show me the full solution in this problem?
Reofrir Reply
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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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