I was solving past exams for my java class and I'm struggling with one of them. I keep getting wrong result and I think its because all of classes and instance variables are static. How do I avoid making them static? Also this question basically wants you to find same letters of the location given in args[1] and convert them to the "S" if they are near of the given location (Args are "K,K,K,Y-K,Y,M,M-K,Y,Y,Y 2,1 S" if you need)
public class MatrixRefill {
public static String[][] matrix;
public static int rows;
public static int cols;
public static String enemy;
public static String target;
public static void main(String[] args) {
target = args[2];
rows = Integer.parseInt(args[1].substring(0,1));
cols = Integer.parseInt(args[1].substring(2));
matrix = matrixCreator(args[0]);
enemy = matrix[rows][cols];
recursive(rows, cols, target);
printer(matrix);
}
public static String[][] matrixCreator(String mx) {
int ro = 0;
int co = 0;
for (int i = 0; i < mx.length(); i++) {
if (mx.substring(i,i+1).equals(","))
co++;
if (mx.substring(i,i+1).equals("-"))
ro++;
}
String[][] matriks = new String[ro+1][co/3+1];
ro = 0;
co = 0;
for (int j = 0; j < mx.length(); j++) {
if (mx.substring(j,j+1).equals(","))
co++;
else if (mx.substring(j,j+1).equals("-")) {
ro++;
co = 0;
}
else
matriks[ro][co] = mx.substring(j,j+1);
}
return matriks;
}
public static void recursive(int row, int col, String target) {
if (valid(row,col)) {
recursive(row+1,col, target);
recursive(row,col+1, target);
recursive(row,col-1, target);
recursive(row-1,col, target);
matrix[row][col] = target;
}
}
public static boolean valid(int row, int col) {
boolean result = false;
if (row >= 0 && row < matrix.length && col >= 0 && col < matrix[row].length)
if (matrix[row][col] == enemy)
result = true;
return result;
}
public static void printer(String[][] owo) {
for(int i = 0; i < owo.length; i++) {
for(int j = 0; j < owo[i].length; j++) {
System.out.print(owo[i][j]);
if(j < owo[i].length - 1)
System.out.print(" ");
}
System.out.println();
}
}
}
Remove the static keyword from your methods and instance fields. But to call them from within main you need to create an instance of the containing class (in this case the one that contains the main method) and use that to call the other methods. What I do sometimes is to create an instance method (i.e. non-static) and call that to start the process. Then everything that would be in main I would put in that method. Here is an example.
public static void main(String[] args) {
MatrixRefill mr = new MatrixRefill();
mr.start();
}
public void start() {
target = args[2];
rows = Integer.parseInt(args[1].substring(0,1));
cols = Integer.parseInt(args[1].substring(2));
matrix = matrixCreator(args[0]);
enemy = matrix[rows][cols];
recursive(rows, cols, target);
printer(matrix);
}
// rest of code here
}
By putting what was in main in the start method you can call the other instance methods and access instance fields without qualifying them with a reference to the class (i.e. in this case prefixing with mr.)
Related
My question is: how can I see the Tuple result in the process method if it was created in the check method? How am I able to use it there, if it was created in a private method?
public class Problem13 {
private Tuple<Integer> costs;
private Tuple<String> names;
private Tuple<Integer> result;
private int budget;
private int minDelta, minCost, totalCost;
public void process(String fileName) {
if (!read(fileName))
return;
if (budget >= totalCost) {
System.out.println("You can buy all items");
return;
}
if (budget < minCost) {
System.out.println("You cannot buy items");
return;
}
minDelta = -1;
int n = costs.getLength();
Set<Integer> interval = new IntegerInterval(0, n - 1);
for (int k = n - 1; k > 0; --k) {
Combinations<Integer> combinations = new Combinations<Integer>(interval, k);
combinations.produce((tuple) -> !check(tuple));
if (minDelta == 0)
break;
}
if (result == null)
System.out.println("No solution found");
else {
int k = result.getLength();
for (int j = 0; j < k; ++j)
System.out.printf("%s ", names.get(result.get(j)));
System.out.printf("(%d)\n", minDelta);
}
}
public static void main(String[] args) {
new Problem13().process("data/input13.txt");
}
private boolean check(Tuple<Integer> tuple) {
int k = tuple.getLength();
int currentCost = 0;
for (int i = 0; i < k; ++i) {
int j = tuple.get(i);
currentCost += costs.get(j);
if (currentCost > budget)
return false;
}
int d = budget - currentCost;
if (minDelta < 0 || d < minDelta) {
minDelta = d;
result = new ArrayTuple<>(k);
for (int i = 0; i < k; ++i)
result.set(i, tuple.get(i));
}
return minDelta == 0;
}
private means private to the class. So Problem13 can see anything defined in that class, whether private, public, protected or package private.
Also, the access modifier of the method only affects who can call it, not where the results can be seen. For instance, if result was defined as a public field, any class (not just Problem13) could see it.
You can find many good breakdowns of access modifiers out there on the Interwebs. Here's one.
I am working on a project and my code isn't working not sure why. Given the test program and general class I need a program that satisfies the following logical regular epxression:
L1: For alphabet {a,b}, all strings that contain an odd number of a's and exactly one b.
Test input: aabaaaa, aaabaaaa, aabaaaab, baaaaaa, aaaaabaa
What it should be:
aabaaaa False
aaabaaaa True
aabaaaab false
baaaaaa false
aaaaabaa True
Program output:
(ture, true, true, false, true)
My Test program:
import java.util.Scanner;
// Test Finite State Machine Class
public class TestFSML1
{
public static void main(String[] args){
String A = "ab";
int[][] ST = {{1,3,0},
{1,2,1},
{2,2,2},
{3,3,3}};
int[] AS = {0,0,1,0};
Scanner in = new Scanner(System.in);
String inString;
boolean accept1 = false;
FSM FSM1 = new FSM(A, ST, AS);
// Input string is command line parameter
System.out.println(" Input Accepted:");
for(int i=0;i<args.length;i++) {
inString = args[i];
accept1 = FSM1.validString(inString);
System.out.printf("%10s%13s\n",inString, accept1);
}
} // end main
} // end class
FSM Class
// Finite State Machine Class
public class FSM
{
// Instance variables
public String alphabet;
public int stateTrans[][];
public int acceptState[];
private int cstate;
// Constructor function
public FSM(String A, int[][] ST, int[] AS)
{
int NSYMBOLS = A.length();
int NSTATES = AS.length;
// Alphabet
alphabet = "" + A;
// State transition table
stateTrans = new int[NSTATES][NSYMBOLS];
for(int r = 0; r < NSTATES; r++)
for(int c = 0; c < NSYMBOLS; c++)
stateTrans[r][c] = ST[r][c];
// Accept states
acceptState = new int[NSTATES];
for(int r = 0; r < NSTATES; r++)
acceptState[r] = AS[r];
// Start state
cstate = 0;
}
// Methods
public int getState()
{
return cstate;
}
public void setState(int state)
{
cstate = state;
return;
}
public int nextState(char symbol)
{
int nstate = -1;
int col = alphabet.indexOf(symbol);
if(col >= 0)
nstate = stateTrans[cstate][col];
return nstate;
}
public boolean accept(int state)
{
if(state < 0)
return false;
return (acceptState[state] != 0);
}
public boolean validString(String word)
{
cstate = 0;
for(int k = 0; k < word.length(); k++){
cstate = nextState(word.charAt(k));
System.out.print(cstate);
System.out.println(" " + word.charAt(k));
if(cstate < 0)
return false;
}
return accept(cstate);
}
} // end class
Thanks!
Here's a simple method I typed up to perform the task you wanted.
public static boolean validWord(String s) {
int aCounter = 0;
int bCounter = 0;
char c;
for (int i = 0; i < s.length(); i++) {
c = s.charAt(i);
if ((int) c == (int) 'a') {
aCounter++;
} else {
bCounter++;
}
}
return (aCounter % 2 == 1 && bCounter == 1);
}
I had trouble understanding how you were implementing your method, and I think it could be much simpler. I'm sure the instance variables you included in the FSM class serve some other use, but I you don't really need any of them to analyze the string. Just use something like this, it should be easy enough to integrate into your code as all it takes is the string. Hope this helps!
I want to replace all multiples of 2 in my array with the value 0 and I felt as though this code did this but 4,6 and 8 stay the same in the output.
Am I doing something stupidly wrong?
public static void markOfMultiples(int[]listOfNumbers, int number)
{
for(int i = 0; i<listOfNumbers.length; i++)
{
if (listOfNumbers[i]%number == 0)
{
listOfNumbers[i] = 0;
}
}
}
In mycase your method was working fine,It solely depends how you are invoking your method
You should invoke your method like
public static void main(String[] args)
{
int num[]={2,4,6,11,13,8};
markOfMultiples(num,2);
}
Your method remains the same
public static void markOfMultiples(int[]listOfNumbers, int number)
{
for(int i = 0; i<listOfNumbers.length; i++)
{
if (listOfNumbers[i]%number == 0)
{
listOfNumbers[i] = 0;
}
System.out.println(listOfNumbers[i]);//added by me to track what's going on
}
and its working fine!
So I have to create a program where I use polymorphism and inheritance to create arrows that point left and arrow and I did that. however, when I created my main class and try to invoke the methods, say for example "LeftArrow.drawHere" to draw the arrow i get errors saying I cannot make a static reference to the non static field "drawHere() from the class LeftArrow". I was wondering then if I can't do that how can I design my main method so it draws the arrows?
here is my code, note that there are several classes but I will post all of them here.
import java.util.Scanner;
public class LeftArrow extends ShapeBasic
{
private int tail, width;
private static int inside;
public LeftArrow()
{
super();
tail = 0;
width = 0;
}
public LeftArrow(int noff, int ntail, int nwidth)
{
super(noff);
tail = ntail;
setWidth(nwidth);
}
public void setTail(int ntail)
{
tail = ntail;
}
public int getTail()
{
return tail;
}
public void setWidth(int nwidth)
{
if (nwidth % 2 == 1)
{
width = nwidth;
}
else
{
System.out.println(" Width must be odd");
System.out.println("Enter a new width");
Scanner key = new Scanner(System.in);
int wid = key.nextInt();
setWidth(wid);
}
}
public int getWidth()
{
return width;
}
public void drawHere()
{
drawTriangle();
drawTail();
drawBTriangle();
//System.out.println();
}
public void drawTriangle()
{
inside = 1;
int split = (width/2);
skipSpaces(getOffset());
System.out.println('*');
for(int count = 0; count < split; count ++)
{
skipSpaces(getOffset() - (inside + 1));
System.out.print('*');
skipSpaces(inside);
System.out.print('*');
inside = inside + 2;
System.out.println();
}
}
public void drawTail()
{
skipSpaces(getOffset() - getInside() - 1);
System.out.print('*');
skipSpaces(getInside());
for (int count = 0; count < tail ; count++)
{
System.out.print('*');
}
}
public void drawBTriangle()
{
int inside = getInside();
int split = (width/2);
System.out.println();
for(int count = 0; count < split; count ++)
{
skipSpaces(getOffset() - (inside - 1));
System.out.print('*');
inside = inside - 2;
skipSpaces(inside);
System.out.print('*');
System.out.println();
}
skipSpaces(getOffset());
System.out.print('*');
}
public int getInside()
{
return inside;
}
private static void skipSpaces(int number)
{
for (int count = 0; count < number; count++)
System.out.print(' ');
}
#Override
public void setOffset(int noff) {
// TODO Auto-generated method stub
}
#Override
public int getOffset() {
// TODO Auto-generated method stub
return 0;
}
}
import java.util.Scanner;
public class RightArrow extends ShapeBasic
{
private int tail, width;
private static int inside;
public RightArrow()
{
super();
tail = 0;
width = 0;
}
public RightArrow(int noff, int ntail, int nwidth)
{
super(noff);
tail = ntail;
setWidth(nwidth); // must be odd
}
public void setTail(int ntail)
{
tail = ntail;
}
public int getTail()
{
return tail;
}
public void setWidth(int nwidth)
{
if (nwidth % 2 == 1)
{
width = nwidth;
}
else
{
System.out.println(" Width must be odd");
System.out.println("Enter a new width");
Scanner key = new Scanner(System.in);
int wid = key.nextInt();
setWidth(wid);
}
}
public int getWidth()
{
return width;
}
public void drawHere()
{
drawTriangle();
drawTail();
drawBTriangle();
System.out.println();
}
public void drawTail()
{
skipSpaces(getOffset() + 1);
for (int count = 0; count < tail ; count++)
{
System.out.print('*');
}
skipSpaces(getInside());
System.out.print('*'); // fix
}
public void drawTriangle()
{
inside = 1;
int split = (width/2);
skipSpaces(getOffset() + tail);
System.out.println('*');
for(int count = 0; count < split; count ++)
{
skipSpaces(getOffset() + tail);
System.out.print('*');
skipSpaces(inside);
System.out.print('*');
inside = inside + 2;
System.out.println();
}
}
public void drawBTriangle()
{
int inside = getInside();
int split = (width/2);
System.out.println();
for(int count = 0; count < split; count ++)
{
skipSpaces(getOffset() + tail);
System.out.print('*');
inside = inside - 2;
skipSpaces(inside);
System.out.print('*');
System.out.println();
}
skipSpaces(getOffset() + tail);
System.out.print('*');
}
public int getInside()
{
return inside;
}
private static void skipSpaces(int number)
{
for (int count = 0; count < number; count++)
System.out.print(' ');
}
}
public abstract class ShapeBase implements ShapeInterface {
private int offset;
public abstract void drawHere();
public void drawAt(int lineNumber) {
for (int count = 0; count < lineNumber; count++)
System.out.println();
drawHere();
}
}
public class ShapeBasic implements ShapeInterface
{
private int offset;
public ShapeBasic()
{
offset = 0;
}
public ShapeBasic( int noff)
{
offset = noff;
}
public void setOffset(int noff)
{
offset = noff;
}
public int getOffset()
{
return offset;
}
public void drawAt(int linnumber)
{
for (int count = 0; count < linnumber; count++)
System.out.println();
drawHere();
}
public void drawHere()
{
for (int count = 0; count < offset; count++)
System.out.print(' ');
System.out.println('*');
}
}
public interface ShapeInterface
{
public void setOffset(int noff); // set how many space from left
public int getOffset(); // returns offset
public void drawAt(int linnumber); // moves down equal to line number Ex. 5 = 5 down
public void drawHere(); // draws shape after moving left equal to offset
}
I'd ask to see your main method, but I don't have the reputation.
At a guess, I'd say maybe you are not actually instantiating objects of these classes in your main method, but trying to call the methods from them. If, for instance, you do this:
LeftArrow lArrow = new LeftArrow();
lArrow.drawHere();
it should work.
The method drawHere is declared as non-static. Instead of LeftArrow.drawHere() you should call
LeftArrow left = new LefArrow(a, b, c);
left.drawHere();
main is static. It needs to create instances of LeftArrow before it can use them. Something like this:
LeftArrow myArrow = new LeftArrow();
myArrow.drawHere();
I am attempting to write a simple Genetic Algorithm in Java after reading a book on Machine Learning and have stumbled on the basics. I'm out of practice with Java so I'm probably missing something extremely simple.
Individual
public class Individual {
int n;
int[] genes = new int[500];
int fitnessValue;
public int getFitnessValue() {
return fitnessValue;
}
public void setFitnessValue(int fitnessValue) {
this.fitnessValue = fitnessValue;
}
public int[] getGenes() {
return genes;
}
public void setGenes(int index, int gene) {
this.genes[index] = gene;
}
public int getN() {
return n;
}
public void setN(int n) {
this.n = n;
}
// Constructor
public Individual() {
}
}
Population
import java.util.Random;
public class Population {
public Population() {
}
public static void main(String[] args) {
Random rand = new Random();
int p = rand.nextInt(10);
int n = rand.nextInt(10);
Individual pop[] = new Individual[p];
System.out.println("P is: " + p + "\nN is: " + n);
for(int j = 0; j <= p; j++) {
for(int i = 0; i <= n; i++) {
pop[j].genes[i] = rand.nextInt(2);
}
}
}
public void addPopulation() {
}
}
The aim of this code is to populate the Population and the Genes with a random number. Could someone please take a look at my code to see where I'm going wrong?
before
pop[j].genes[i] = rand.nextInt(2);
add
pop[j] = new Individual();
the elements of the array are null.
I believe you need to initialize pop[j] before doing pop[j].genes[i] = rand.nextInt();
Individual pop[] = new Individual[p];
This just initializes the array, not the individual elements. Try to put pop[j] = new Individual() between your two loops.
What they said...
Also, do you mean to call your setGenes method, or do you just want to directly access the gene array.
From what I understand of your code I think you need to do this:
for(int j = 0; j <= p; j++) {
pop[j] = new Individual();
for(int i = 0; i <= n; i++) {
pop[j].setGenes(i, rand.nextInt(2));
}
}