Java Programming - classes and lists
Hi.
I have been given a problem to java problem to solve. I have written most of the code but I am unsure of where to go from here.
Could I please email someone my problem, someone who might be able to help?
I would rather not post the details on here. (I know that sounds stupid, as I came here for help, but I would rather do it privately.)
Any help would be greatly appreciated.
this site only.:)
Regards
manu
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I'm in a java programming class and i'm stuck.. so please help me guys...
Please help me, i really need help.
Thanks a lot guys...
this is my error:
C:\Temp>java Lab2
Welcome!
This program computes the average, the
exams
The lowest acceptable score is 0 and th
Please enter the minimum allowable scor
Please enter the maximum allowable scor
Was Exam1taken?
Please Enter Y N or Q
y
Enter the Score for Exam1:
65
Was Exam2taken?
Please Enter Y N or Q
y
Enter the Score for Exam2:
32
Was Exam3taken?
Please Enter Y N or Q
y
Enter the Score for Exam3:
65
Was Exam4taken?
Please Enter Y N or Q
y
Enter the Score for Exam4:
32
Was Exam5taken?
Please Enter Y N or Q
y
Enter the Score for Exam5:
32
Score for Exam1 is:65
Score for Exam2 is:32
Score for Exam3 is:32
Score for Exam4 is:32
Score for Exam5 is:32
the Minimum is:0
the Maximum is:0
Can't compute the Average
Can't compute the Variance
Can't compute the Standard Deviation
this is my code:
// Lab2.java
// ICS 21 Fall 2002
// Read in scores for a student's exams, compute statistics on them, and print out
// the scores and statistics.
public class Lab2
// Create a manager for this task and put it to work
public static void main(String[] args)
ExamsManager taskManager = new ExamsManager();
taskManager.createResults();
// ExamsManager.java for Lab 2
// ICS 21 Fall 2002
// make these classes in the Java library available to this program.
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
import java.text.NumberFormat;
// ExamsManager creates managers and contains the tools (methods) they need to do their
// job: obtaining exam information, computing statistics and printing out that information
class ExamsManager
// INVALID_INT: special integer value to indicate that a non-integer
// was entered when an integer was requested. It's chosen so as not to
// conflict with other flags and valid integer values
public static final int INVALID_INT = -9999;
// valid user response constants:
public static final String YES = "Y"; // user responded "yes"
public static final String NO = "N"; // user responded "no"
public static final String EXIT_PROGRAM = "Q"; // user responded "leave the program NOW"
// INVALID_RESPONSE: special String value to indicate that something other than
// "Y", "N" or "X" was entered when said was required
public static final String INVALID_RESPONSE = "!";
// ABSOLUTE_MIN_SCORE and ABSOLUTE_MAX_SCORE represent the smallest
// minimum score and the largest maximum score allowed by the
// program. (The allowable minimum and maximum for one
// execution of the program may be different than these, but
// they must both lie within this range.)
public static final int ABSOLUTE_MIN_SCORE = 0;
public static final int ABSOLUTE_MAX_SCORE = 1000;
// The manager needs a place to store this student's exams
private OneStudentsWork thisWork;
// ...places to store the min and max scores allowed for these exams
private int minAllowedScore;
private int maxAllowedScore;
// ...and a place to hold input coming from the keyboard
BufferedReader console;
// -------------------- Constructor --------------------
// ExamsManager() make managers that delegate the major tasks of the program
public ExamsManager()
// -------------------- Processing methods --------------------
// createResults() is the "manager at work": it calls assistants to welcome the user,
// initializes things so we can read info from the keyboard,
// obtain the minimum and maximum allowed scores,
// obtain a student's work and comute the statistics on it and
// print out the scores and the statistics
public void createResults()
// *** YOUR CODE GOES HERE ***
printWelcomeMessage();
readyKeyboard();
obtainMinAndMaxAllowedScores();
obtainOneStudentsWork();
printResults();
// -------------------- User input methods --------------------
// readyKeyboard() sets up an input stream object 'console' connected to the keyboard
// so that what's typed can be read into the program and processed.
// Do not modify this code!
private void readyKeyboard()
console = new BufferedReader(new InputStreamReader(System.in));
// obtainMinAndMaxAllowedScores() asks the user to enter the minimum
// and maximum allowable scores for this execution of the program.
// Both the minimum and maximum allowable scores must be between
// ABSOLUTE_MIN_SCORE and ABSOLUTE_MAX_SCORE (inclusive). This
// method should continue to ask the user for a minimum until a
// valid one is entered (or EXIT_PROGRAM is entered), then continue
// to ask the user for a maximum until a valid one is entered. If
// the minimum entered is greater than the maximum entered, the
// whole thing should be done again.
public void obtainMinAndMaxAllowedScores()
// *** YOUR CODE GOES HERE ***
int response = INVALID_INT;
if (response >= minAllowedScore && response <= maxAllowedScore)
System.out.print("Please enter the minimum allowable score:");
response = getIntOrExit();
while (response > maxAllowedScore || response < minAllowedScore)
System.out.print("Please enter the minimum allowable score:");
response = getIntOrExit();
if (response <= ABSOLUTE_MAX_SCORE && response >= ABSOLUTE_MIN_SCORE)
System.out.print("Please enter the maximum allowable score:");
response = getIntOrExit();
while (response > ABSOLUTE_MAX_SCORE || response < ABSOLUTE_MIN_SCORE)
System.out.print("Please enter the maximum allowable score:");
response = getIntOrExit();
/*int response;
String allowedMin;
boolean done = true;
do
done = true;
System.out.print("Please enter the minimum allowable score:");
response = getIntOrExit();
allowedMin = getYNOrExit();
if(allowedMin == EXIT_PROGRAM)
System.exit(0);
else if (response >= ABSOLUTE_MIN_SCORE)
done = true;
else if (response >= ABSOLUTE_MAX_SCORE)
done = false;
System.out.println("INVALID: " + INVALID_INT);
System.out.print("Please enter the minimum allowable score:");
response = getIntOrExit();
}while (!done);
/* System.out.print("Please enter the maximum allowable score:");
response = getIntOrExit();
if (response <= ABSOLUTE_MAX_SCORE)
return response;
else if (response <= ABSOLUTE_MIN_SCORE)
response = INVALID_INT;
while (response == INVALID_INT)
System.out.print("Please enter the maximum allowable score:");
response = getIntOrExit();
do
done = true;
System.out.print("Please enter the minimum allowable score:");
response = getIntOrExit();
String allowedMax;
if(allowedMin == EXIT_PROGRAM)
System.exit(0);
if (response <= ABSOLUTE_MAX_SCORE)
done = true;
else if (response <= ABSOLUTE_MIN_SCORE)
done = false;
System.out.println("INVALID: " + INVALID_INT);
System.out.print("Please enter the maximum allowable score:");
response = getIntOrExit();
}while (!done);
// The overall strategy to building up a student work object is
// to have the student-bulding method call on the exam-building
// method, which calls upon user input methods to get exam info.
// Thus, user entered info is successively grouped together
// into bigger units to build the entire student information set.
// obtainOneStudentsWork() builds the five exams
// and constructs the student work object from them
private void obtainOneStudentsWork()
// *** YOUR CODE GOES HERE ***
int index = 1;
Exam exam1 = buildOneExam(index);
index = 2;
Exam exam2 = buildOneExam(index);
index = 3;
Exam exam3 = buildOneExam(index);
index = 4;
Exam exam4 = buildOneExam(index);
index = 5;
Exam exam5 = buildOneExam(index);
thisWork = new OneStudentsWork(exam1, exam2, exam3, exam4, exam5);
// buildOneExam(thisTest) reads the exam information for one exam and returns an
// Exam object constructed from this information. Uses obtainWasExamTaken() to
// determine if the exam was taken and obtainOneScore() to get the exam score, if needed.
private Exam buildOneExam(int thisTest)
// *** YOUR CODE GOES HERE ***
int score = 0;
if(obtainWasExamTaken(thisTest))
score = obtainOneScore(thisTest);
return new Exam(score);
else
return new Exam();
System.out.println("Enter score for exam1:");
Exam exam1 = new Exam(getIntOrExit());
System.out.println("Enter score for exam2:");
Exam exam2 = new Exam(getIntOrExit());
System.out.println("Enter score for exam3:");
Exam exam3 = new Exam(getIntOrExit());
System.out.println("Enter score for exam4:");
Exam exam4 = new Exam(getIntOrExit());
System.out.println("Enter score for exam5:");
Exam exam5 = new Exam(getIntOrExit());
// obtainWasExamTaken(thisTest) keeps asking the user whether 'thisTest' was taken
// (e.g., "Was exam 1 taken? Enter Y, N or Q", if thisTest equals 1)
// until s/he provides a valid response. If Q is entered, we leave the
// program immediately; if Y or N (yes or no), return true if yes, false if no
private boolean obtainWasExamTaken(int thisTest)
// *** YOUR CODE GOES HERE ***
String response = INVALID_RESPONSE;
System.out.println("Was Exam" + thisTest + "taken?");
while (response.equals(INVALID_RESPONSE))
System.out.println("Please Enter" + " " + YES + " " + NO + " " + "or" + " " + EXIT_PROGRAM);
response = getYNOrExit();
if (response.equals(YES))
return true;
else
return false;
// obtainOneScore(thisTest) keeps asking the user to enter a score for
// 'thisTest' (e.g., "Enter the score for exam 1", is thisTest equals 1)
// until s/he provides one within range or s/he tells us to exit the program.
private int obtainOneScore(int thisTest)
// *** YOUR CODE GOES HERE ***
int response = INVALID_INT;
if (response >= minAllowedScore && response <= maxAllowedScore);
System.out.println("Enter the Score for Exam" + thisTest + ":");
response = getIntOrExit();
while (response > ABSOLUTE_MAX_SCORE || response < ABSOLUTE_MIN_SCORE)
System.out.println("INVALID: " + INVALID_INT);
System.out.println("Please Enter again:");
response = getIntOrExit();
return response;
// scoreIsWithinRange() returns true if the given score is inside of
// the allowable range and false if it is out of range
private boolean scoreIsWithinRange(int score)
// *** YOUR CODE GOES HERE ***
if (score >= minAllowedScore && score <= maxAllowedScore)
return true;
else
return false;
// getYNQ() reads a String from the console and returns it
// if it is "Y" or "N" or exits the program if "Q" is entered;
// the method returns INVALID_RESPONSE if the response is other
// than"Y", "N" or "Q".
// Do not modify this code!
private String getYNOrExit()
String usersInput = INVALID_RESPONSE;
try
usersInput = console.readLine();
catch (IOException e)
// never happens with the keyboard...
usersInput = usersInput.toUpperCase();
if (usersInput.equals(EXIT_PROGRAM))
System.out.println("Leaving...");
System.exit(0);
if (usersInput.equals(YES) || usersInput.equals(NO))
return usersInput;
else
return INVALID_RESPONSE;
// getIntOrExit() reads an integer from the console and returns it.
// If the user types in "Q", the program exits. If an integer is entered,
// it is returned. If something that is not an integer (e.g. "Alex"), the
// program returns INVALID_INT
// Do not modify this code!
private int getIntOrExit()
String usersInput = "";
int theInteger = 0;
try
usersInput = console.readLine();
catch (IOException e)
// never happens with the keyboard...
// if the user wants to quit, bail out now!
if(usersInput.toUpperCase().equals(EXIT_PROGRAM))
System.out.println("Program halting at your request.");
System.exit(0);
// see if we have an integer
try
theInteger = Integer.parseInt(usersInput);
catch (NumberFormatException e)
// user's input was not an integer
return INVALID_INT;
return theInteger;
// -------------------- User output methods --------------------
// printWelcomeMessage() prints a welcome message to the user explaining
// what the program does and what it expects the user to do. In
// particular, it needs to tell the user the absolute lowest and
// highest acceptable exam scores
private void printWelcomeMessage()
// *** YOUR CODE GOES HERE ***
System.out.println("Welcome!");
System.out.println("This program computes the average, the variance, and the standard deviation of 5 exams");
System.out.println("The lowest acceptable score is 0 and the highest is 1000");
// printResults() prints all of the scores present, then prints the
// statistics about them. The statistics that can have factional parts
// -- average, variance and standard deviation -- should be printed with
// exactly three digits after the decimal point. If a statistic could not be
// computed, a message to that effect should print (NOT the "phony" value stored
// in the statistic to tell the program that the statistic could not be computed).
public void printResults()
// These statements create a NumberFormat object, which is part
// of the Java library. NumberFormat objects know how to take
// doubles and turn them into Strings, formatted in a particular
// way. First, you tell the NumberFormat object (nf) how you'd like
// the doubles to be formatted (in this case, with exactly 3
// digits after the decimal point). When printing a double you call
// format to format it -- e.g. nf.format(the-number-to-format)
NumberFormat nf = NumberFormat.getInstance();
nf.setMinimumFractionDigits(3);
nf.setMaximumFractionDigits(3);
// *** YOUR CODE GOES HERE ***
System.out.println("Score for Exam1 is:" + thisWork.getExam1().getScore());
System.out.println("Score for Exam2 is:" + thisWork.getExam2().getScore());
System.out.println("Score for Exam3 is:" + thisWork.getExam3().getScore());
System.out.println("Score for Exam4 is:" + thisWork.getExam4().getScore());
System.out.println("Score for Exam5 is:" + thisWork.getExam5().getScore());
if (thisWork.getStatistics().getMinimum() == Statistics.CANT_COMPUTE_STATISTIC)
System.out.println("Can't compute the Minimum");
else
System.out.println("the Minimum is:" + thisWork.getStatistics().getMinimum());
if (thisWork.getStatistics().getMaximum() == Statistics.CANT_COMPUTE_STATISTIC)
System.out.println("Can't compute the Minimum");
else
System.out.println("the Maximum is:" + thisWork.getStatistics().getMaximum());
if (thisWork.getStatistics().getAverage() == Statistics.CANT_COMPUTE_STATISTIC)
System.out.println("Can't compute the Average");
else
System.out.println("the Average is:" + thisWork.getStatistics().getAverage());
if (thisWork.getStatistics().getVariance() == Statistics.CANT_COMPUTE_STATISTIC)
System.out.println("Can't compute the Variance");
else
System.out.println("the Variance is:" + thisWork.getStatistics().getVariance());
if (thisWork.getStatistics().getStandardDeviation() == Statistics.CANT_COMPUTE_STATISTIC)
System.out.println("Can't compute the Standard Deviation");
else
System.out.println("the Standard Deviation is:" + thisWork.getStatistics().getStandardDeviation());
// OneStudentsExams.java for Lab 2
// ICS 21 Fall 2002
// OneStudentsWork is the exams and the statistics computed from
// them that comprise one student's work
class OneStudentsWork
public static final int NUMBER_OF_EXAMS = 5;
// The student is offered five exams...
private Exam exam1;
private Exam exam2;
private Exam exam3;
private Exam exam4;
private Exam exam5;
// The statistics on those exams
Statistics studentStats;
// -------------------- Constructor --------------------
// Takes five constructed exam objects and store them for this student.
// Constructs a statistics object that holds the stats for these exams and
// store it in studentStats.
public OneStudentsWork(Exam test1, Exam test2, Exam test3, Exam test4, Exam test5)
// *** YOUR CODE GOES HERE ***
exam1 = test1;
exam2 = test2;
exam3 = test2;
exam4 = test4;
exam5 = test5;
studentStats = new Statistics(test1, test2, test3, test4, test5);
// -------------------- Accessor methods --------------------
// getExamX() methods make available ExamX
public Exam getExam1()
return exam1;
public Exam getExam2()
return exam2;
public Exam getExam3()
return exam3;
public Exam getExam4()
return exam4;
public Exam getExam5()
return exam5;
// getStatistics() makes available the Statistics object that is part of this student's work
public Statistics getStatistics()
return studentStats;
// Statistics.java for Lab 2
// ICS 21 Fall 2002
// A Statistics object stores the statistics for a group of Exams.
class Statistics
// This constant denotes a statistic that cannot be
// computed, such as an average of zero scores or a variance
// of one score.
public static final int CANT_COMPUTE_STATISTIC = -9999;
// The stats
private int minimum;
private int maximum;
private int numberOfExamsTaken;
private double average;
private double variance;
private double standardDeviation;
// -------------------- Constructor --------------------
// Calculates (initializes) the statistics, using passed-in exams.
// Note that the order of computing thst stats matters, as some
// stats use others; for instance, variance must be computed before
// standard deviation.
public Statistics(Exam exam1, Exam exam2, Exam exam3, Exam exam4, Exam exam5)
// *** YOUR CODE GOES HERE ***
calculateAverage(exam1,exam2,exam3,exam4,exam5);
calculateVariance(exam1,exam2,exam3,exam4,exam5);
calculateStandardDeviation(exam1,exam2,exam3,exam4,exam5);
// -------------------- Accessor methods --------------------
// getNumberOfExamsTaken() makes available the number of exams this student undertook
public int getNumberOfExamsTaken()
return numberOfExamsTaken;
// getMinimum() makes the minimum available
public int getMinimum()
return minimum;
// getMaximum() makes the maximum available
public int getMaximum()
return maximum;
// getAverage() makes the average available
public double getAverage()
return average;
// getVariance() make the variance available
public double getVariance()
return variance;
// getStandardDeviation() make the standard deviation available
public double getStandardDeviation()
return standardDeviation;
// -------------------- Statistics methods --------------------
// ---> Note: all statistics are to be computed using the number of exams taken
// calculateNumberOfExamsTaken() computes the number of tests the student took
// and stores the result in 'numberOfExamsTaken'
// (Note this statistic can always be computed.)
private void calculateNumberOfExamsTaken(Exam exam1, Exam exam2, Exam exam3, Exam exam4, Exam exam5)
// *** YOUR CODE GOES HERE ***
numberOfExamsTaken = OneStudentsWork.NUMBER_OF_EXAMS;
// calculateMinimum() sets 'minimum' to the minimum score of exams taken, or
// to CANT_COMPUTE_STATISTIC if a minimum can't be computed.
private void calculateMinimum(Exam exam1, Exam exam2, Exam exam3, Exam exam4, Exam exam5)
// *** YOUR CODE GOES HERE ***
/*min = exam1.getScore();
if (min > exam2.getScore())
min = exam2.getScore();
if (min > exam3.getScore())
min = exam3.getScore();
if (min > exam4.getScore())
min = exam4.getScore();
if (min > exam5.getScore())
min = exam5.getScore();
if(numberOfExamsTaken == 0)
minimum = CANT_COMPUTE_STATISTIC;
else if(numberOfExamsTaken == 1)
minimum = exam1.getScore();
else
minimum = exam1.getScore();
if(numberOfExamsTaken >= 2 && numberOfExamsTaken <= minimum)
minimum = exam2.getScore();
if(numberOfExamsTaken >= 3 && numberOfExamsTaken <= minimum)
minimum = exam3.getScore();
if(numberOfExamsTaken >= 4 && numberOfExamsTaken <= minimum)
minimum = exam4.getScore();
if(numberOfExamsTaken >= 5 && numberOfExamsTaken <= minimum)
minimum = exam5.getScore();
if (getMinimum() == ExamsManager.ABSOLUTE_MIN_SCORE)
minimum = exam1.getScore();
//exam1.getScore() = getMinimum();
else
exam1.getScore() = CANT_COMPUTE_STATISTIC;
// calculateMaximum() sets 'maximum' to the maximum score of exams taken, or
// to CANT_COMPUTE_STATISTIC if a maximum can't be computed.
private void calculateMaximum(Exam exam1, Exam exam2, Exam exam3, Exam exam4, Exam exam5)
// *** YOUR CODE GOES HERE ***
/*if (maximum == ExamsManager.ABSOLUTE_MAX_SCORE)
return true;
else
return CANT_COMPUTE_STATISTIC;*/
max = exam1.getScore();
if (max < exam2.getScore())
max = exam2.getScore();
if (max < exam3.getScore())
max = exam3.getScore();
if (max < exam4.getScore())
max = exam4.getScore();
if (max < exam5.getScore())
max = exam5.getScore();
if(numberOfExamsTaken == 0)
maximum = CANT_COMPUTE_STATISTIC;
else if(numberOfExamsTaken == 1)
maximum = exam1.getScore();
else
maximum = exam1.getScore();
if(numberOfExamsTaken >= 2 && numberOfExamsTaken >= maximum)
maximum = exam2.getScore();
if(numberOfExamsTaken >= 3 && numberOfExamsTaken >= maximum)
maximum = exam3.getScore();
if(numberOfExamsTaken >= 4 && numberOfExamsTaken >= maximum)
maximum = exam4.getScore();
if(numberOfExamsTaken >= 5 && numberOfExamsTaken >= maximum)
maximum = exam5.getScore();
// calculateAverage() computes the average of the scores for exams taken and
// stores the result in 'average'. Set to CANT_COMPUTE_STATISTIC if there
// are no tests taken.
private void calculateAverage(Exam exam1, Exam exam2, Exam exam3, Exam exam4, Exam exam5)
// *** YOUR CODE GOES HERE ***
if (numberOfExamsTaken == 5)
average = (exam1.getScore()+exam2.getScore()+exam3.getScore()+exam4.getScore()+exam5.getScore()/OneStudentsWork.NUMBER_OF_EXAMS);
else if (numberOfExamsTaken == 4)
average = (exam1.getScore()+exam2.getScore()+exam3.getScore()+exam4.getScore()/OneStudentsWork.NUMBER_OF_EXAMS);
else if (numberOfExamsTaken == 3)
average = (exam1.getScore()+exam2.getScore()+exam3.getScore()/OneStudentsWork.NUMBER_OF_EXAMS);
else if (numberOfExamsTaken == 2)
average = (exam1.getScore()+exam2.getScore()/OneStudentsWork.NUMBER_OF_EXAMS);
else if (numberOfExamsTaken == 1)
average = (exam1.getScore()/OneStudentsWork.NUMBER_OF_EXAMS);
else if (numberOfExamsTaken == 0)
average = CANT_COMPUTE_STATISTIC;
// calculateVariance() calculates the returns the variance of the
// scores for exams taken and stores it in 'variance'
// For a small set of data (such as this one), the formula for calculating variance is
// the sum of ((exam score - average) squared) for scores of exams taken
// divided by (the number of scores - 1)
// Set to CANT_COMPUTE_STATISTIC if there are fewer than two tests taken.
private void calculateVariance(Exam exam1, Exam exam2, Exam exam3, Exam exam4, Exam exam5)
// *** YOUR CODE GOES HERE ***
if (numberOfExamsTaken == 5)
variance = ((exam1.getScore()-average)*(exam1.getScore()-average)+(exam2.getScore()-average)*(exam2.getScore()-average)+(exam3.getScore()-average)*(exam3.getScore()-average)+(exam4.getScore()-average)*(exam4.getScore()-average)+(exam5.getScore()-average)*(exam5.getScore()-average))/4;
else if (numberOfExamsTaken == 4)
variance = ((exam1.getScore()-average)*(exam1.getScore()-average)+(exam2.getScore()-average)*(exam2.getScore()-average)+(exam3.getScore()-average)*(exam3.getScore()-average)+(exam4.getScore()-average)*(exam4.getScore()-average))/4;
else if (numberOfExamsTaken == 3)
variance = ((exam1.getScore()-average)*(exam1.getScore()-average)+(exam2.getScore()-average)*(exam2.getScore()-average)+(exam3.getScore()-average)*(exam3.getScore()-average))/4;
else if (numberOfExamsTaken == 2)
variance = ((exam1.getScore()-average)*(exam1.getScore()-average)+(exam2.getScore()-average)*(exam2.getScore()-average))/4;
else if (numberOfExamsTaken < 2)
variance = CANT_COMPUTE_STATISTIC;
// calculateStandardDeviation() calculates the standard
// deviation of the scores of taken exams and stores
// it in 'standardDeviation'
// The formula for calculating standard deviation is just
// the square root of the variance
private void calculateStandardDeviation(Exam exam1, Exam exam2, Exam exam3, Exam exam4, Exam exam5)
// *** YOUR CODE GOES HERE ***
if (variance == CANT_COMPUTE_STATISTIC)
standardDeviation = CANT_COMPUTE_STATISTIC;
else
standardDeviation = (Math.sqrt(variance));
// Exam.java for Lab 2
// ICS 21 Fall 2002
// An Exam object stores information about one exam
class Exam
private boolean examTaken; //was the exam taken? true for yes, false for no
private int score; //the exam's score; = 0 if test not taken
// -------------------- Constructors --------------------
// Construct a taken exam; it has score 's'
public Exam(int s)
score = s;
examTaken = true;
// Construct an exam not taken; it has a score of 0
public Exam()
score = 0;
examTaken = false;
// -------------------- Accessor methods --------------------
// Make the score of an exam available
public int getScore()
return score;
// Make available whether an exam was taken
public boolean wasTaken()
return examTaken;Your code is absolutely unreadable - even if someone was willing to
help, it's simply impossible. I do give you a few tips, though: If you
understand your code (i.e. if it really is YOUR code), you should be
able to realize that your minimum and maximum never get set (thus they
are both 0) and your exam 3 is set with the wrong value. SEE where
those should get set and figure out why they're not. Chances are you
are doing something to them that makes one 'if' fail or you just
erroneously assign a wrong variable! -
Java abstract classes and methods
Can anyone please tell me any real time example of abstract classes and methods.
I want to know its real use. If anyone have ever used it for some purpose while programming please do tell me.Ashu_Web wrote:
No please.. I just want to know if you have used it while programming. Like "an abstract class can be used to put all the common method names in it without having to write actual implementation code."That would describe an Interface better than an abstract class. Abstract classes usually have at least some implementation.
I want to know its usage in programming, not just a definition. I guess you understand what I am looking for.Yes, and I gave you one: java.util.AbstractList. It can be found inside the src.zip in your JDK directory and it is a pretty good example for an abstract class that provides some implementation and defines exactly what is necessary to make a full List implementation. -
Running a Java program over and over.........
I'm new to java development, so forgive me if this is the wrong forum, or just a stupid question. What I have is a java program that reads messages from an IBM MQseries queue using the MQseries AMI interface, makes a connection to an oracle database, and inserts those messages into a table in the database. What I need, however, is for the program to run over and over, checking the queue for messages, and sending them to the database. How do I get this java program to constantly run. Also, when it runs the first time, I need to make a connection to the oracle database, grab some information from a table, and stick it into a java array. I only need this done once. Is there an init() method or something I can put this code in so it will only be done once?
Information that needs to only be run once can be done two ways.
1) Inside a constructor. This code will run each time you instantiate an object.
2) Inside a static block. Runs once, and only once, regardless of how many instances are created
Here's the example of both.
public class Foo
static
System.out.println("I'm in the static block");
public Foo()
System.out.println("I'm in the constructor");
}Also, check out java.util.Timer for scheduling tasks to reoccur at regular intervals. -
Intermittent problem in Coldfusion 9, BlazeDS with Java Service class and CFCProxy
If that title doesn't scare you, you might be able to help.
I believe there is a bug in Coldfusion 9's version of CFCProxy.
Tech Stack:
Flex Application
BlazeDS (stock with CF9)
Java Service class (java-amf BlazeDS endpoint)
Coldfusion business tier, invoked by the Java Service class using CFCProxy
Tomcat 6 on Java 1.6
Linux or Windows servers, both exhibit same behavior
SQL Server database
Problem:
When Flex calls a Java service method through BlazeDS that invokes a Coldfusion CFC through CFCProxy, and the method called in the Coldfusion CFC includes a large query (10 fields, 1000+ records returned), we intermittently (1 out of ~5 times) receive the following exception:
java.lang.NullPointerException
at coldfusion.runtime.NeoPageContext.popBody(NeoPageContext.java:1925)
at coldfusion.filter.SilentFilter.invoke(SilentFilter.java:57)
at coldfusion.runtime.UDFMethod$ReturnTypeFilter.invoke(UDFMethod.java:405)
at coldfusion.runtime.UDFMethod$ArgumentCollectionFilter.invoke(UDFMethod.java:368)
at coldfusion.filter.FunctionAccessFilter.invoke(FunctionAccessFilter.java:55)
at coldfusion.runtime.UDFMethod.runFilterChain(UDFMethod.java:321)
at coldfusion.runtime.UDFMethod.invoke(UDFMethod.java:220)
at coldfusion.runtime.TemplateProxy.invoke(TemplateProxy.java:491)
at coldfusion.runtime.TemplateProxy.invoke(TemplateProxy.java:437)
at coldfusion.cfc.CFCProxyFilter.invoke(CFCProxyFilter.java:56)
at coldfusion.filter.ApplicationFilter.invoke(ApplicationFilter.java:381)
at coldfusion.filter.ClientScopePersistenceFilter.invoke(ClientScopePersistenceFilter.java:2 8)
at coldfusion.filter.GlobalsFilter.invoke(GlobalsFilter.java:38)
at coldfusion.filter.DatasourceFilter.invoke(DatasourceFilter.java:22)
at coldfusion.cfc.CFCProxy.doInvoke(CFCProxy.java:281)
at coldfusion.cfc.CFCProxy.invoke(CFCProxy.java:193)
at com.lampo.mapping.service.MapToolWebService.makeCfcProxyCall(MapToolWebService.java:1326)
at com.lampo.mapping.service.MapToolWebService.getTerritoryList(MapToolWebService.java:609)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at flex.messaging.services.remoting.adapters.JavaAdapter.invoke(JavaAdapter.java:418)
at flex.messaging.services.RemotingService.serviceMessage(RemotingService.java:183)
at flex.messaging.MessageBroker.routeMessageToService(MessageBroker.java:1400)
at flex.messaging.endpoints.AbstractEndpoint.serviceMessage(AbstractEndpoint.java:1005)
at flex.messaging.endpoints.amf.MessageBrokerFilter.invoke(MessageBrokerFilter.java:103)
at flex.messaging.endpoints.amf.LegacyFilter.invoke(LegacyFilter.java:158)
at flex.messaging.endpoints.amf.SessionFilter.invoke(SessionFilter.java:44)
at flex.messaging.endpoints.amf.BatchProcessFilter.invoke(BatchProcessFilter.java:67)
at flex.messaging.endpoints.amf.SerializationFilter.invoke(SerializationFilter.java:166)
at flex.messaging.endpoints.BaseHTTPEndpoint.service(BaseHTTPEndpoint.java:291)
at flex.messaging.MessageBrokerServlet.service(MessageBrokerServlet.java:353)
at coldfusion.flex.ColdfusionMessageBrokerServlet.service(ColdfusionMessageBrokerServlet.jav a:114)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at coldfusion.bootstrap.BootstrapServlet.service(BootstrapServlet.java:89)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.j ava:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at coldfusion.filter.FlashRequestControlFilter.doFilter(FlashRequestControlFilter.java:71)
at coldfusion.bootstrap.BootstrapFilter.doFilter(BootstrapFilter.java:46)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.j ava:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.jk.server.JkCoyoteHandler.invoke(JkCoyoteHandler.java:190)
at org.apache.jk.common.HandlerRequest.invoke(HandlerRequest.java:291)
at org.apache.jk.common.ChannelSocket.invoke(ChannelSocket.java:769)
at org.apache.jk.common.ChannelSocket.processConnection(ChannelSocket.java:698)
at org.apache.jk.common.ChannelSocket$SocketConnection.runIt(ChannelSocket.java:891)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:690)
at java.lang.Thread.run(Thread.java:662)
Attempts to diagnose:
These things remove the problem:
CF8 works perfectly with the identical code, never fails.
Calling the same Coldfusion CFC method with the large query (10 fields, 1000+ records returned) from another CFC 100+ times never fails.
Using a Coldfusion service class (a "my-cfamf" BlazeDS endpoint) never fails. However, we need to use a Java service class because we are using ~40 Java value objects (VOs) that correspond to ~40 auto-generated Actionscript VOs. BlazeDS won't correctly deserialize the Actionscript VOs into the Java VOs with a Coldfusion service class.
If I replace the large query with a Sleep(5000) instead, it never fails.
These things don't remove the problem:
Using the latest Microsoft JDBC driver doesn't help.
Even if the Coldfusion method returns an empty resultset (i.e., just calls the query and doesn't do any other work or return anything), the call still fails intermittently.
If the Coldfusion CFC with the method in question is instantiated and stored in SERVER scope as a singleton across multiple requests with CFCProxy, doesn't help.
Different large (1000+ record queries) all fail in the same way.
Caching the query doesn't help
Changes in the datasource configuration doesn't help
Using the older version of BlazeDS doesn't help
With all of these tests, I believe it comes down to a problem in the combination between CFCProxy and large queries. There may be more to it, but that is what we've narrowed it down to.
Any insight would be very welcome.Hi Frank
The page is ADF bound, I've added the page source and the adfc-config source below :
Page
<?xml version='1.0' encoding='UTF-8'?>
<jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" version="2.1"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:af="http://xmlns.oracle.com/adf/faces/rich">
<jsp:directive.page contentType="text/html;charset=UTF-8"/>
<f:view>
<af:document id="d1">
<af:form id="f1">
<af:commandButton text="commandButton 1" id="cb1"
actionListener="#{test.testws}"/>
</af:form>
</af:document>
</f:view>
</jsp:root>adfc-config
<?xml version="1.0" encoding="windows-1252" ?>
<adfc-config xmlns="http://xmlns.oracle.com/adf/controller" version="1.2">
<view id="view1">
<page>/view1.jspx</page>
</view>
<managed-bean id="__4">
<managed-bean-name id="__3">test</managed-bean-name>
<managed-bean-class id="__2">ch.mit.test.test</managed-bean-class>
<managed-bean-scope id="__1">request</managed-bean-scope>
</managed-bean>
</adfc-config>It seems to be the same sort of problem as in Re: Error in ADF Web Service Connection
Regards
Paul -
Executing a Java -- program.class
1234JLG - Please help me resolve this hurdle. I do JAVAC and generate a Class, that I can display with NOTEPAD, but when I do JAVA, what I receive is ...
Error occurred during initialization of VM
java/lang/NoClassDefFoundError: java/lang/object
Thank You So Much.This is thrown if the Java Virtual Machine tries to load in the class and no definition of the class could be found.
Make sure the path to the class is correct or execute from same directory. -
Can anyone recommend a good training class that covers Java programming with enterprise portals, i.e, Java IView development, etc.
ThanksHi,
do you had a look at:
http://www.sap.com/services/education/index.epx
Regards
Gregor -
HTTP connection between two java programs(classes)
Hello everyone,
here's my question:
I need to create two java applications(just two console apps) that can exchange data with each other only via the HTTP protocol. I guess I have to use the URLConnection class. How can I do that? Basically I need to make one app work as a server and the other one just as a simple client.
thanks in advanceURLConnection.
As for the server, you could use a Servlet. There are Java libraries that act as a servlet container without requiring installation. Jetty comes to mind. -
Java Runtime class and CloneNotSupportedException
I'm trying to execute an operating system command via a Java Stored Procedure but it fails with the following message:
Exception caught executing command.
java.lang.CloneNotSupportedException
at java.lang.Object.clone(Object.java)
at java.lang.Runtime.exec(Runtime.java)
at java.lang.Runtime.exec(Runtime.java)
at java.lang.Runtime.exec(Runtime.java)
at Host.Execute(Host.java:10)
Why? Here is my java source:
public class Host {
public static int Execute(String[] aCommand) throws IOException {
int rtnVal;
try {
Process pid = Runtime.getRuntime().exec(aCommand);
rtnVal = pid.waitFor();
catch (Exception e) {
e.printStackTrace();
rtnVal = -1;
return rtnVal;John,
I don't have an answer for you, just some suggestions.
The problem may be related to the command you are trying to execute. Does your code not work for any command you try?
Also, your java method takes a "String[]" parameter. There is no standard mapping between a java "String[]" and a PL/SQL type. What is your (PL/SQL) call spec for this method?
According to the code you have posted, the "Execute()" method swallows all "Exception"s -- since your code catches them and merely prints out the stack trace. So is the stack trace you posted from the printed out stack trace (from your "catch" block) -- or is it an "uncaught" exception? Since "CloneNotSupportedException" is a subclass of "Exception", I guess the former is correct, right?
Also, since your code catches "Exception"s, and since "IOException" is a subclass of "Exception", there's not much point in declaring that your method "throws IOException". So what's the point of the declaration?
By the way, I couldn't find any mention in your post of the database version you are using. Posting that detail may be helpful (in getting you an answer to your question).
Good Luck,
Avi. -
Creating and running JARs from Java programs
OK, I have been googling and searching, but this is something I cannot work out, so I raelly need some help.
Basically, I am building a GUI app that would generate, compile and run java programs. And I also want to enable the users to create JARs they can later double-click if they want to run the program.
I am using Runtime to compile programs and it works just fine. When I click on a button to create a JAR, my application creates one, but when I double-click on it, it can't find main and it exits. Now that is not so much unusual, but I am positive that my manifest file is OK, because when I run the same command from the command line, then I can click on the JAR file to run it.
So what is the deal here? I mean, why would a JAR file created from the command line run and the one created through a GUI app using the very same command could not find main?
Any help would be graetly appreciated.again, another unanswered question.
BTW I'l keep bumping these until I get an answer that works. I have been up 3 hours now trying to get this sorted and it's something that netbeans is supposed to do on its own!?!?!?!?!
Hello, SUN, is there anyone there???
No, didn't think so. -
How to interchange data between Java Program and C++ Program
I constructed a java program using netbeans IDE that has ability to connect with a respective DLL; I want to connect and interchange data between my java program(.jar) and VSC++ program(.exe) through DLLs.JNI uses single Dll to invoke C/C++ function in native manner,In order to increase the efficiency I tried to connect and interchange primitive data types between Java program and C++ program using that DLL(JNI implemented).
Unfortunately C++ program cannot obtain data values that has been changed by Java Program.For example - If I declare a global int variable in DLL,java program can catch that int variable and can update it but If I run my C++ program(exe) loading same DLL simultaneously it cannot receive the updated value of that int variable declared in the DLL.
Therefore I need a solution to share/Interchange at least primitive data and their respective values between a JAVA and C++ Program using JNI (in spite of date transferring through Sockets).JAVA TO C/C++ & C/C++ to JAVA using DLLs.
(TWO WAY COMMUNICATION)
JAVA.jar <=> <JNI> <=> DLL <=> [Connector Program C/C++] <=> C/C++ .exe
PLEASE HELP ME!! THANK YOUWhat in the are you trying to say? What does "filled into the servlet mean?" Is the map somewhere outside the servlet? In a different process? Are you asking how to extract data from a map? Something else?
Sorry, but your question makes no sense. -
What are the major differences between Java programming language and HTML or XML and why is it better?
Thanks for your response but I am dumb when it comes
to this stuff. I am taking an information systems
class and the professor is asking us to list three
different items that makes Java different from other
programming languages used and I thought posing that
question to this form would provide me the
information I was looking for. The text does not
state the answer he is looking for. Any help would be
great.
ThanksI'd assume your professor is asking you to do something called "research" where you go read stuff about it/them. What you're doing is called "just ask someone to tell some answers to turn in as my own", or in other words, "cheating". -
JSP codes for running a JAVA program
hello...
does anyone know the JSP codes for running a Java program from my web page?? i mean i already have my java program compiled... and i just want this java program to run in the background when I click on a button or a link...
Any idea about this?
plz advice..
aviyes... u r somewhat right... but this runs on Jakarta Tomcat...
i'm using the Apache Http Server together with the ServletExec AS which enable the Apache server to run JSP..
I've created a package where i've put my classes...
WEB-INF/classes/tbd(package name)/my classes
and i've added.. package name.. in my java program..
and then in jsp... i've written..
<%@ page import="tdb.*"%>
<jsp:useBean id="exec" class="tdb.textdb" />
<%exec.convert_data();%>
but when i run the page it says the package does not exist...
can anyone tell where to place the folder WEB-INF so that it can run fine?
thx
avi -
How to import custom java jar/class into oracle to be used in java proc ?
Hi
I would like to know how to import custom java jar/class files into oracle to be used in java stored procedure.
I am developing a oracle pl/sql procedure to call java program. The java program will be created as procedure and will be published.
But, my question is that I do have a other external jar/class file that need to be imported into this java program.
example
raise_sal.java
import java.util.*;
import oracle.sql.*;
<<reference other java programs >>
import cmpmsgsvc.xxxx.* ;
import cmpmsgsvc.yyyy.* ;
import cmpmsgsvc.zzzz.* ;
how do I import the cmpmsgsvc jar/class file into oracle so that I don't have any
compilation errros on raise_sal.java program ??
what are the steps to import/compile and validate to do this?
thanks for your help in advance.
Thanks
rrb.Kuassi
Problem is that, I have 6 jar files that are needed to be included in the main java program. And, there are more than 50+ classes, propertiers in those 6 jar files.
It might be not good idea to have all those 50+ classes in the production database.
Is there anyway that I keep all those 6 jar files in unix box (our's is oracle erp installation with oracle being installed on unix box) and just refer them in the main java program. I mean database will be loaded with main java program and it should able to refer other 6 jar files from unix.
if we create a directory and keep all jar files in there and include that directory in classpath variable, does this works? or what is other method?
Please let me know.
Thanks -
Making a java program work on windows xp platforma without developer kit
hi to you all!
I've written some programs in java but until now I only had to compile and run them on my machine so there were no problems until now.
I need now to write a little very easy program for a friend of mine and some other people who could need to use it. My friend said he wants a very "user-friendly" program so no command in ms dos prompt or stuff like that. I'm trying to make a .exe of my java program using "exe4j", is that good?
second question: many of the people who will use my program have no idea of what java programming is and I don't think they want to download jdk and jre cause they won't be of any use to them, so how can I avoid this?
is it possible?
Thank you very much.Put the jre folder from your JDK install in your app folder.ok, but in this way he doesn't have to download jre
but I have to add it to the app folder so that an
application large just some kilobytes would become
some megas bigger... unless I have misunderstood what
you're suggesting me of course.Yeah, that's the downside. However, 17 MB isn't very large by todays standards.
jre\javaw -cp <your classpath> <your main class><your classpath> is the class i need to be run's path
or my classpath?
jre\javaw has to be written like this or preceeded by
the path of jre directory?As long as you point 'start in' to the correct directory, I don't believe you have to worry about that. That path you have there isn't quite right (neither was mine) but I think you've got that under control.
You can give anm explicit path, then you can have different users with different start-in values and store their properties there automatically.
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