<< Chapter < Page Chapter >> Page >
Label[] A = new Label[2];

Elements initialized to null

This is a two-element array. When first created, it contains two elements, each having a default value of null . What this really means is that the reference values stored in each of the two elements don't initially refer toany object.

Populate the array elements

The next fragment creates two instances (objects) of the Label class and assigns those object's references to the two elements in the arrayobject. This is perfectly valid.

A[0] = new Label("O");A[1] = new Label("K");

You cannot add reference values

The problem arises in the next fragment. Rather than dealing with the object's references in an appropriate manner, this fragment attempts toaccess the text values of the two reference variables and concatenate those values.

System.out.println(A[0] + A[1]);

The compiler produces the following error message:

Ap055.java:14: error: bad operand types for binary operator '+' System.out.println(A[0]+ A[1]);^ first type: Labelsecond type: Label 1 error

This error message is simply telling us that it is not legal to add the values of reference variables.

Not peculiar to arrays

This problem is not peculiar to arrays. You would get a similar error if you attempted to add two reference variables even when they aren't stored in anarray. In this case, the code to access the values of the elements is good. The problem arises when we attempt to do something illegal with those values afterwe access them.

Usually two steps are required

Therefore, except in some special cases such as certain operations involving the wrapper classes, to use Java arrays with types other than the primitive types, whenyou access the value stored in an element of the array (a reference variable) you must perform only those operations on that reference variable that are legalfor an object of that type. That usually involves two steps. The first step accesses the reference to an object. The second step performs some operation onthe object.

Back to Question 7

Answer 6

C. 3

Explanation 6

Once you create an array object for a primitive type in Java, you can treat the elements of the array pretty much as you would treat the elements of anarray in other programming languages. In particular, a statement such the following can be used to assign a value to an indexed element in an arrayreferred to by a reference variable named A .

A[1] = 2;

Similarly, when you reference an indexed element in an expression such as the following, the value stored in the element is used to evaluate the expression.

System.out.println(A[0] + A[1]);

For all Java arrays, you must remember to create the new array object and to store the array object's reference in a reference variable of the correct type. Then you can use the reference variable to gain access to the elements inthe array.

Back to Question 6

Answer 5

B. Runtime Error

Explanation 5

Good fences make good neighbors

One of the great things about an array object in Java is that it knows how to protect its boundaries.

Unlike some other currently popular programming languages, if your program code attempts to access a Java array element outside its boundaries, anexception will be thrown. If your program doesn't catch and handle the exception, the program will be terminated.

Questions & Answers

how environment affect demand and supply of commodity ?
Amos Reply
Wht at the criteria for market ?
Amos
what is difference between monitory policy and fiscal policy?
Malik Reply
monetary policy is a policy thrust by National Govt(CBN) to influence government spending, purchase &taxes
Frank
necessity of economics
Pamela Reply
I will say want,choice,opportunity cost,scarcity,scale of preference
Alao
what is monopoly market.How price output are determined under monopoly market
bisham
b) Monopoly market is an impecfect market where s single firm having the innovation to produce a particular commodity.Prices are determined through output since there are no other competitive.
Frank
Monopoly market:firm has market power & does not respond to market price
Frank
Explain the process of price determination under perfect competition market with suitable diagram
bisham Reply
Price determination under perfect competition via this process :firms have no market power to influence price rather firms respond to market price.
Frank
price is different from demand- demand is amount of commodity
Effah Reply
demand is amount /quantity of commodity a potential buyer is willing to buy at a given price at market
Frank
demand is a desire of customer on commodity with the ability to pay it and willing to buy it at given price of commodity
Harika
demand is price of what
Faith Reply
show that shortrun average cost
Baby Reply
what is economics
Mbah Reply
what is money
Mbah
what is money
Mbah
Difine macro economics
agaba
money is a medium of exchange between goods and services,maybe inform of currency.
Wesonga
Economics is study of how human beings strive to satisfy numerous wants using limited available resources.
Wesonga
how do you find the maximum number of workers the firms should employ order to produce where there are increasing returns
Jane
what are implications of computing national income?.
agaba
pl
MUDASIRU
what is the formulae for calculating national income
MUDASIRU
it calculated by value added method
Praveen
classify the production units like agriculture, banking, transport etc
Praveen
money is anything that is generally acceptetable for human
Ogbaji
Estimate the net value added(NVA) at fixed cost by each industrial structure
Praveen
definition of unemployment
Adam Reply
what are the causes of unemployment?
Mbubi Reply
The main causes of unemployment are listed below. 1. Frictional unemployment 2. Cyclical unemployment 3. Structural unemployment
assani
We can also categorize the causes on a broader sense as: 1. Political and 2. Social cause As unemployeement root causes are embaded in this two.
Yonathan
would opportunity cost exist if there was no scarcity?
assani
yes just because the opportunity cost arose when there is Alternative to choose among the alternatives.
BADAMASIU
I am thinking that, if our resources were unlimited, then there wouldn't be any need to forgo some wants. Hence the inexistence if opportunity cost
assani
Politics
Job
politics has done what?
assani
consider time assani
Mary
I'm Emmanuel,...I taught the main cause is the change in gov't.
Emmanuel
...Lack of capital to set up a firm respectively
Emmanuel
🙈
Emmanuel
I would like to bring in Educational levels can also be the cause the cause of the problem respectively
Emmanuel
I think the main causes of unemployment is lack of INFRASTRUCTURAL DEVELOPMENT OVER POPULATION OVER DEPENDENT ON GOVERNMENT LACK OF SELF EMPOWERMENT...
ananti
lack of skills among the new generation is the serious issue.
Vishal
Where I come from , I don't see why education or personal aspects seem to do with unimployment, technically the motivation and eigerness in all works of live is there , dispite the cultural influence and physical bearriors;the thing we lacking is Government Support and open market ethics.
Joe
sorry about that-(repation). We have a over powering ethical political system that's displacing the marketing asspects of economy and causing large scale unemployment right across the board...
Joe
can someone Explain Expansionary Monetary Policy and Contractionary Monetary Policy Using one of the instrument of Monetary Policy? Please am kinda lost here?. ta
Emmanuel Reply
using a graph show the case of substitute and compliment goods
Ade Reply
can anyone give me a simple explanation to Five Sector Macroeconomics?
Emmanuel
Can someone please define what economics is
jason Reply
economics simply is a social science subject that study human behavior.
dajan
economics is a social science which studies human behaviour as a relationship between ends and scarce means that has alternative uses
Alao
Can someone please tell me how to calculate GDP
Emmanuel
emmanual kapal to calculate GDP (Gross Domestic Product) has three method in calculating it (1)income approach (2) expenditure approach (3) value added method
Alao
thanks Alae
Emmanuel
u are welcome
Alao
in basic terms economics is revered to as battery system, it date back to when Men sees the need to exchange sapless goods and produce to gain , either wealth , basic necessities or to establish trading ties for personal benefit or social asspects in terms of coexistence and continuity, future .
Joe
what is the law of demand
Berlinda Reply
keep other thing constant, when the price increases demand decrease when the price decreases demand increases of the commodity.
sj
all things being equal,quantity demanded decrease as price increase and increase as price decrease
Seth
there's practial joke to it ..." the higher the demand ; scarcity, increase in production and drop in quality"... quite the controversy - for example China vs Europe, United States and we are all boxed up in between somewhere...
Joe
Other thing remain constant the low price of commodity the high quantity of commodity and vice versa is true
Baraka
Explain Effective demand
Anita Reply
What is effective demand
Anita
like Modi is in demand...best example of effective demand
Pranav
Don't get you
Anita
Anita you mean you don't get me or who?
Onyeking
level of demand that represents a real intention to purchase by people with the means to pay
Pranav
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





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
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Object-oriented programming (oop) with java' conversation and receive update notifications?

Ask