Sieve Of Eratosthenes Program Using Arrays
Feb 9, 2015
I am trying to figure out the Sieve of Eratosthenes program using arrays. I am trying to display the prime numbers of 1-100. My code right now is:
import java.text.DecimalFormat;
import java.util.Scanner;
public class TextLab06st
{
public static void main(String args[])
{
// This main method needs additions for the 100 point version.
Scanner input = new Scanner(System.in);
System.out.println("
TextLab06
[code]...
I am getting the error <identifier? expected for the line "primes.[index] = false;"
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Jun 27, 2014
I found this method from the same link from which I found the Pandigital method. This method uses the algorithm of sieve of eratosthenes who was a greek mathematician and showed how to find prime numbers by taking an individual number and finding the multiples of it and cut them out for they will not be a prime number. From what I've seen this program gives the results much faster than the traditional way of searching for prime numbers by diving that number by the digits upto half of that number and check for divisiblity.
Well, here's the code
public int[] ESieve(int upperLimit) {
int sieveBound = (int)(upperLimit - 1) / 2;
int upperSqrt = ((int)Math.Sqrt(upperLimit) - 1) / 2;
BitArray PrimeBits = new BitArray(sieveBound + 1, true);
for (int i = 1; i <= upperSqrt; i++) {
if (PrimeBits.Get(i)) {
[Code] .....
As seen from the full program on the site [URL] .... this program was formely writen in C++ and from there I've scrapped out this method as the syntax are corresponding to that of Java, but one problem I faced was in finding the BitArray class in Java. I was unable to understand the approach of this program to find the prime numbers.
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Apr 1, 2015
When I compile the code, it goes through fine in the compiler. However after entering the boundaries for the lower an upper it doesn't produce the prime pairs between the two boundaries that the user sets. I have tried changing some of my integers that i initialized no luck. I looked at the last section of public void showPrimes() . However I can't seem to see where it has gone wrong there. I have included the entire code, plus the section again that I think is wrong. I have also posted the final output of what it looks like and what else should be included to make it easier to see what I am missing. Basically it keeps giving me zero primes even when the boundary is 100 and 200, or so and so forth.
import java.util.Scanner;
public class kbeaudry_xSieve
{
public static void main (String args[]){
kbeaudry_xSieve i = new kbeaudry_xSieve();
}
boolean primes[] = new boolean [50001];
int upper;
int lower;
[code]....
This is what i get when I actually run the program. However in the section where I have added *****, this is where it should put the prime pairs in.
Please enter a lower boundary and an upper boundary and I will print all of the sexy prime pairs between those boundaries.
Please enter the lower boundary (between 1 and 50000): 200
Please enter the upper boundary (between 1 and 50000): 600
There were 0 sexy pairs displayed between 200 and 600.. I am still working on another code for my that I had issues with, however I had to go out of the country for a few days to take care of some work.
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Jan 16, 2015
I am doing a sieve code to find prime numbers.
public static void main(String[] args)
{
Scanner scanner = new Scanner(System.in);
System.out.println(" Enter the maximum number ");
int maxNumber = scanner.nextInt();
int[]numberList = createList (maxNumber);
[code]....
I have a problem with the output. It only get as far as marking the multiples of 2. It does not mark the multiples of 3 and so on.Example output: If the range is from 2 to 15 the output is :2, 3, 0, 5, 0, 7, 0, 9, 0, 11, 0, 13, 0, 15 note: 0 means its marked.As you can see it only marks multiples of 2 but it does not mark multiples of 3 above. I think the problem lies in the for loop inside my main method, because the index does not increment.
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Oct 24, 2014
I'm just learning about arrays. I have a small program to write that asks to create 2 arrays. One holding 5 names of flowers. One holding the prices of those 5 flowers. I ask the user what kind of flower they want and the quantity. I then need to create a loop that locates the flower name and uses that index to find the cost of the flower. I am struggling on how to write in code how to use one array index to find another. Example: Roses and $.50.
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Nov 13, 2014
I am designing a program that generates 3 random numbers from 1-5 and if 2 match, the user wins $1. If 3 match, the user wins respectively:
All 1s - $5
2s - $10
3s - $25
4s - $50
5s - $100
I first used a loop to run until the user runs out of money or wishes to stop. Then I made 2 methods. 1 to generate the random numbers and 1 to see if the user won any money. I am storing the random numbers in an array called slotnumber.
This is what I have so far but I am getting compiling errors at while (cont == 'y') {
import java.util.Scanner;
import java.util.Random;
public class SlotMachine
{
[Code]......
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Feb 14, 2015
I am trying to create a program that reads a sentence, such as: "abba is running to the radar" scans this sentence, and then prints out all the palindromes. I am running into issues with my arrays and for statements. Here is my code:
static String palindrome, backwardsLower,
palindromeLower, palindromeClean, backwards2, backwards = "";
static String[] words;
static int counter;
public static void main(String[] args) {
palindrome = JOptionPane.showInputDialog("Please enter a phrase. " +
[Code] ...
I am aware that there is a few "useless" variables in there at the moment, I will clean them up (as well as some useless statements, I see those too). The issue comes at about line 17. The variable backwards REMOVES all the spaces from the array, so when it comes time to compare the strings, it is comparing individual words to the ENTIRE string, thus no words will ever be a palindrome.
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Nov 19, 2014
Here are the errors I am getting:
SlotMachine.java:21: error: illegal start of expression
public static void getNums(int [] slots)
^
SlotMachine.java:21: error: illegal start of expression
public static void getNums(int [] slots)
[code]....
i keep fixing small things and cannot get it to compile. Below is the original code,
import java.util.Scanner;
import java.util.Random;
public class SlotMachine
{
public static void main (String args[]) {
int userMoney;
Scanner input = new Scanner(System.in);
System.out.print("How much money to start with?
[code]....
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Jan 13, 2014
I am trying to test values stored in 2d arrays once but i my program just keeps looping what am i doing wrong
Java Code:
tempi=i;
tempx=x;
for( i=0;i<3;i++) {
for( x=0;x<4;x++) {
if(rounded[i][x]<395 || rounded[i][x] >405) {
System.out.println("there is an error with probes "+rounded[i][x]);
[Code] .....
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Jul 23, 2014
My assignment is to essentially update a calculator program that uses strings, and methods, to include arrays. How to create and call an array that the user defines the size of and then inputs the numbers to fill the array. Here's the example my prof gave us of what the output should look like:
Menu
1. Add
2. Subtract
3. Multiply
4. Divide
5. Dot product
6. Generate random array
7. Quit
What would you like to do? 1
How many values are in the arrays? 3
Enter the values in the first array, separated by spaces:
2 4 6
Enter the values in the second array, separated by spaces:
1 3 5
The result is [3.0, 7.0, 11.0]
How to create an array that would allow the user to define the size of the array and then inputs the values for the array? I'm completely lost. I never should have taken java as an online class.
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Apr 16, 2014
I am making a gradebook program that calculates the averages of 25 students using 2D arrays in which the students have four test grades. I have figured out how to display the averages of each student in one column but I cant seem to figure out how to display the letter grade of the average into another column.
Right now my program reads from a .txt doc
Heres what I've got.
TestGradeBook.java
import java.util.*;
import java.io.*;
public class TestGradeBook {
public static void main (String [] args ) throws IOException{
//Declarations
final int ROWS = 100;
final int TESTS = 4;
[Code] .....
GradeBook_Data.txt
Name100100100100
// basic name and grades
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Dec 6, 2014
I am trying to create a program for class the uses two dimensional arrays. I am stuck on the second step that states Use two parallel arrays. One is a two-dimensional array -- a row of this array will hold six values in this order: [0] number of hours worked, [1] hourly pay rate, [2] gross pay, [3] net pay, [4] federal withholding, and [5] state withholding.
This is what I have so far:
Java Code:
double [][] data = new double [30][6];
String [] names = new String [30];
String str = null;
String detail = null;
int n = input(data, names, inputFile); mh_sh_highlight_all('java');
(there's more but i don't believe it pertains to this question)
My question is how would I create this array. Or, is that right above? I've searched online and in my book and I just don't understand.
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Dec 2, 2014
Recently I have missed a few weeks of my class due to family emergencies. Because of this I have missed very important lectures. My professor has assigned me the following assignment:
Prices Write a Java program that specifies three one-dimensional arrays names price, amount, and total. Each array should be capable of holding 10 elements. Using a loop, input values for the price and amount arrays. The entries in the total array should be the product of the corresponding values in the price and amount arrays. After all the data have been entered, display the following output:
Total Price Amount
==== ==== ======
Under each column heading display the appropriate value.
I know how to display everything using printf, how to create the actual arrays and define the array size, but I am confused on how and what loop to use and how to construct it. This is what I have managed to write up so far:
import java.util.Scanner; // Imports the Scanner class
import java.text.DecimalFormat; // Imports the DecimalFormat class
public class Prices
{
public static void main(String [] args)
{
double[] price = new double[10];
double[] amount = new double[10];
double[] total = new double[10];
// Create a new Scanner object
Scanner keyboard = new Scanner(System.in);
} //End of main method
} // End of public class
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Jun 28, 2014
I mainly would like to know is a int[4][4] or a int [4*4] is more efficient to use. Which takes more storage? Which requires more to process? that kind of stuff.
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Apr 23, 2015
I'm wonder about the issue of constructor for arrays. Let say I have a class tablica, and one component int[] tab. If I get it right until now tab is nothing more than empty reference to some unexisting array?
import java.util.Random;
class tablica{
int[] tab;
tablica (){ // i wish it was constructor
[code]....
Then, I'm trying to build the constructor for class tablica. What can be the parameter of such constructor? Is it fields of array? It is simple forf for basic variable
- I liken values defined in constructor with those global defined in class. But how to do it with array component tab.
If I create array object in main method then how can I use this constructor?
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Sep 19, 2014
How do i increase the size of a 2D array from 2X2 to 4X4 where only the boundary elements are zeroes and the rest of them remain the same?
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Jan 28, 2015
In the program below I populated three arrays: student id, name, and GPA. The findStudent() method attempts to match users input with the input stored in the studentID array using an if/ else statement. When I use the if/ else statement the else always executes regardless if the IDs match? I am trying to get JOptionPane.showMessageDialog(null, "Incorrect entry"); to print only if the IDs don't match.
Java Code:
//FILE: StudentIDArray.java
import javax.swing.*; //Used for the JOption dialog boxes
import java.util.*; //Used for Scanner input
public class StudentIDArray {
boolean nameFound = true;
final int numOfElements = 2; //Final int to control to loop for data
[code]....
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Aug 22, 2014
I'm working on a side project, which will eventually hopefully be a Pokedex, and I've just been going to it at the end of every chapter and using the stuff I've learned to work on it.So I just read chapter 3, which is all about variables and teaches how to use arrays.
my question is, does an array have to be declared inside a method? Because I'm trying to create an array inside a class without any methods and without the main, and I continuously get errors. Here's a quick working of my code that won't compile.
class blah {
blah a[] = new blah[7];
a[0] = new blah();
}
The error message focuses on a[0] = new blah(); Telling me the 0 should be a ], the = is an illegal start of type, so on and so forth. The program compiles completely fine if it's within a method, like this:
class blah {
void a() {
blah a[] = new blah[7];
a[0] = new blah();
}
}
Or if I have public static void main (String[]args); But I'm trying to practice working outside of main.So does an array have to be within a method,
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Nov 22, 2014
I have created a class and a matrix of doubles (or at least, I think I have, that's partly what I want to verify).I need to return the values of the array,Here is my class:
public class example{
double[][] Position=new double[2][11];
double calculate(){
for (int time=0;time<=10;time=time+1){
Position[1][time]=time;
Position[2][time]=time+1;
double A=Position[2][time];
return A;
}
}
}
I am getting the error: "This method must return a result of type double", though to me it looks like I am returning double (A).
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Mar 15, 2015
I am having trouble conceptualizing how to fill arrays. I understand that I can declare one and number it's elements, and it stores values of a certain data types. I don't really understand beyond that. Like how I would fill and use data in it.
I can be more specific with an assignment I have for school, but need to get started understanding how to fill arrays with data and then how to use that data.
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Sep 21, 2014
So im making this ghost game where i display an 8x8 filled with 0s and a randomly generator five 1s in there I can get it to display 0s and add 1s, however sometimes the 1s that are randomly generated sometimes go on the same spot making it look like there are only four 1s. How would i go about fixing that?
package Grade12;
import java.util.Random;
public class Ghost {
public static void main(String[] args) {
Random generator = new Random();
int gameboard [][] = new int [8][8];
int randomx, randomy, counter = 0, sum = 0;
for(int row = 0; row < 8; row++){
for(int col = 0; col < 8; col++){
(gameboard[row][col]) = 0;
}
[code]...
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Mar 4, 2014
The assignment goes like this...Write a Payroll class that uses the following arrays as fields:
employeeID - An array of seven integers to hold employee identification numbers. The array should be initialized with the following numbers:
5658845452012578951228777541
845127713028507580489
hours - An array of seven integers to hold the number of hours worked by each employee.payRate - An array of seven doubles to hold each employee's hourly pay rate.wages - An array of seven doubles to hold each employee's gross wages.The class should relate the data in each array through the subscripts.
For example, the number in element 0 of the hours array should be the number of hours worked by the employee whose identification number is stored in element 0 of the employeeID array. That same employee's pay rate should be stored in element 0 of the payRate array. In addition to the appropriate accessor and mutator methods, the class should have a method that accepts an employee's identification number as an argument and returns the gross pay for that employee.Demonstrate the class in a complete program that displays each employee number and asks the user to enter that employee's hours and pay rate. It should then display each employee's identification number and gross wages.Input Validation: Do not accept negative values for hours or numbers less than 6.0 for a pay rate.
My problem with this program is that everytime I try to print the employee ID's or the wages, I get hashcode or something like it (#[I1a77cdc or something like that). I tried using the toString method, but it lists all of the values, when I'm trying to display one at a time. Here is the code for the class:
// moduleArray class
public class moduleArray {
final int NUM_EMPLOYEES = 7;
int[] employeeID = {5658845, 4520125, 7895122, 8777541, 8451277, 1302850, 7580489};
int[] hours = new int[NUM_EMPLOYEES];
[code]...
This is the demo program to list the ID's. I've been messing with it for some time, and right now I just want it to display values.
import java.util.Scanner;
public class moduleArrayDemo {
public static void main(String[] args) {
final int NUM_EMPLOYEES = 7;
int[] ID = new int[NUM_EMPLOYEES];
[code]...
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Dec 14, 2014
Okay, so the assignment was creating a word search for the given array. I've created all the code necessary, but I've ran into trouble. This problem occurs with the Up-Forward, Up-Backward, Down-Forward, and Down-Backward sections. If I only set one of these to run, it works. But if I have all 4 set at the same time, it errors out on the first one that runs.
public class P_WordSearch {
public static void main(String[] args) {
char[][] puzzle = {
{'B','O','O','G','S','R','O','W','I','N','G'},
{'E','B','L','G','N','I','M','M','I','W','S'},
{'L','C','E','A','T','I','P','U','P','I','S'},
{'C','M','I','N','C','A','X','Y','O','S','N'},
[Code] ....
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Dec 15, 2014
I am trying to concatenate two arrays but on on compiling it is showing
Java Code: import static java.util.Arrays.*;
class Mergesort
{
public static void main(String...s)
{
Mergesort r=new Mergesort();
int x[]={1,2,3,4,5,6};
int y[]={9,8,7,15,14,13,12,11};
[Code]...
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Jan 4, 2015
I am receiving one error when using arrays and methods. It's at the bottom of the code and I have commented what the error is .
import java.io.*;
import javax.swing.*;
public class CEO_PROGRAM_PartB
{
public static void main (String[] args) throws IOException
[code]....
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Dec 5, 2014
The assignment was to create 3 parallel arrays to make a student database.The first array will contain 4 digit student id's, the second a string array with student names, and the third array is student gpa's. The user is to receive a dialog box asking to enter the student id, and if the id is correct the user is to see the student name and grade. If the user input does not match any value in the student id array, the user is to receive a message stating invalid id. Here is the code I have so far.
For some reason no matter what the user enters, the information for the last array entry is displayed.
public class parallelStudent
{
public static int sequentialSearch(int[] array, int value)
{
int index; //loop control variable
int element; //element the value is found at
boolean found; //flag indicating search results
[code]...
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