public class Matrix {
public static int a = 0;
public static int b = 0;
public double myArray[][];
public Matrix(double a[][]) {
this.myArray = a;
}
public Matrix(int b, Vector... vectors) {
double myArray[][] = new double[vectors.length][];
int row = vectors.length;
Matrix.a = row;
int column = vectors[0].getYourArray().length;
Matrix.b = column;
for (int i = 0; i < row; i++) {
myArray[i] = new double[row];
}
for (int i = 0; i < row; i++) {
for (int j = 0; j < column; j++) {
if (b == 0) {
double[] a = vectors[i].getYourArray();
myArray[i][j] = a[j];
} else {
myArray[j][i] = vectors[i].getYourArray()[j];
}
}
}
}
public class Vector {
double yourArray[];
public double[] getYourArray() {
return yourArray;
}
public void setYourArray(double[] yourArray) {
this.yourArray = yourArray;
}
public Vector(double... yourArray) {
this.yourArray = yourArray;
}
}
}
I create 2 vectors array and send them into vector class to make an array which includes these two vectors parameters and then send to matrix class to create matrices with dimension of vector arrays
The problem is that how can i determine the rows and columns of new matrix?
I cannot write a proper code guys please help me
As you see it in your code:
1-th dimension: vectors.length
2-th dimension: vectors[0].getYourArray().length
Normally you also have to ensure, that for all vectors[0].getYourArray() the length is the same.
I'm trying to create a Java program with threads for matrix multiplication. This is the source code:
import java.util.Random;
public class MatrixTest {
//Creating the matrix
static int[][] mat = new int[3][3];
static int[][] mat2 = new int[3][3];
static int[][] result = new int[3][3];
public static void main(String[] args) {
//Creating the object of random class
Random rand = new Random();
//Filling first matrix with random values
for (int i = 0; i < mat.length; i++) {
for (int j = 0; j < mat[i].length; j++) {
mat[i][j] = rand.nextInt(10);
}
}
//Filling second matrix with random values
for (int i = 0; i < mat2.length; i++) {
for (int j = 0; j < mat2[i].length; j++) {
mat2[i][j] = rand.nextInt(10);
}
}
try {
//Object of multiply Class
Multiply multiply = new Multiply(3, 3);
//Threads
MatrixMultiplier thread1 = new MatrixMultiplier(multiply);
MatrixMultiplier thread2 = new MatrixMultiplier(multiply);
MatrixMultiplier thread3 = new MatrixMultiplier(multiply);
//Implementing threads
Thread th1 = new Thread(thread1);
Thread th2 = new Thread(thread2);
Thread th3 = new Thread(thread3);
//Starting threads
th1.start();
th2.start();
th3.start();
th1.join();
th2.join();
th3.join();
} catch (Exception e) {
e.printStackTrace();
}
//Printing the result
System.out.println("\n\nResult:");
for (int i = 0; i < result.length; i++) {
for (int j = 0; j < result[i].length; j++) {
System.out.print(result[i][j] + " ");
}
System.out.println();
}
}//End main
}//End Class
//Multiply Class
class Multiply extends MatrixTest {
private int i;
private int j;
private int chance;
public Multiply(int i, int j) {
this.i = i;
this.j = j;
chance = 0;
}
//Matrix Multiplication Function
public synchronized void multiplyMatrix() {
int sum = 0;
int a = 0;
for (a = 0; a < i; a++) {
sum = 0;
for (int b = 0; b < j; b++) {
sum = sum + mat[chance][b] * mat2[b][a];
}
result[chance][a] = sum;
}
if (chance >= i)
return;
chance++;
}
}//End multiply class
//Thread Class
class MatrixMultiplier implements Runnable {
private final Multiply mul;
public MatrixMultiplier(Multiply mul) {
this.mul = mul;
}
#Override
public void run() {
mul.multiplyMatrix();
}
}
I just tried on Eclipse and it works, but now I want to create another version of that program in which, I use one thread for each cell that I'll have on the result matrix. For example I've got two 3x3 matrices. So the result matrix will be 3x3. Then, I want to use 9 threads to calculate each one of the 9 cells of the result matrix.
Can anyone help me?
You can create n Threads as follows (Note: numberOfThreads is the number of threads that you want to create. This will be the number of cells):
List<Thread> threads = new ArrayList<>(numberOfThreads);
for (int x = 0; x < numberOfThreads; x++) {
Thread t = new Thread(new MatrixMultiplier(multiply));
t.start();
threads.add(t);
}
for (Thread t : threads) {
t.join();
}
Please use the new Executor framework to create Threads, instead of manually doing the plumbing.
ExecutorService executor = Executors.newFixedThreadPool(numberOfThreadsInPool);
for (int i = 0; i < numberOfThreads; i++) {
Runnable worker = new Thread(new MatrixMultiplier(multiply));;
executor.execute(worker);
}
executor.shutdown();
while (!executor.isTerminated()) {
}
With this code i think that i resolve my problem. I don't use synchronized in the methods but i think that is not necessary in that case.
import java.util.Scanner;
class MatrixProduct extends Thread {
private int[][] A;
private int[][] B;
private int[][] C;
private int rig, col;
private int dim;
public MatrixProduct(int[][] A, int[][] B, int[][] C, int rig, int col, int dim_com) {
this.A = A;
this.B = B;
this.C = C;
this.rig = rig;
this.col = col;
this.dim = dim_com;
}
public void run() {
for (int i = 0; i < dim; i++) {
C[rig][col] += A[rig][i] * B[i][col];
}
System.out.println("Thread " + rig + "," + col + " complete.");
}
}
public class MatrixMultiplication {
public static void main(String[] args) {
Scanner In = new Scanner(System.in);
System.out.print("Row of Matrix A: ");
int rA = In.nextInt();
System.out.print("Column of Matrix A: ");
int cA = In.nextInt();
System.out.print("Row of Matrix B: ");
int rB = In.nextInt();
System.out.print("Column of Matrix B: ");
int cB = In.nextInt();
System.out.println();
if (cA != rB) {
System.out.println("We can't do the matrix product!");
System.exit(-1);
}
System.out.println("The matrix result from product will be " + rA + " x " + cB);
System.out.println();
int[][] A = new int[rA][cA];
int[][] B = new int[rB][cB];
int[][] C = new int[rA][cB];
MatrixProduct[][] thrd = new MatrixProduct[rA][cB];
System.out.println("Insert A:");
System.out.println();
for (int i = 0; i < rA; i++) {
for (int j = 0; j < cA; j++) {
System.out.print(i + "," + j + " = ");
A[i][j] = In.nextInt();
}
}
System.out.println();
System.out.println("Insert B:");
System.out.println();
for (int i = 0; i < rB; i++) {
for (int j = 0; j < cB; j++) {
System.out.print(i + "," + j + " = ");
B[i][j] = In.nextInt();
}
}
System.out.println();
for (int i = 0; i < rA; i++) {
for (int j = 0; j < cB; j++) {
thrd[i][j] = new MatrixProduct(A, B, C, i, j, cA);
thrd[i][j].start();
}
}
for (int i = 0; i < rA; i++) {
for (int j = 0; j < cB; j++) {
try {
thrd[i][j].join();
} catch (InterruptedException e) {
}
}
}
System.out.println();
System.out.println("Result");
System.out.println();
for (int i = 0; i < rA; i++) {
for (int j = 0; j < cB; j++) {
System.out.print(C[i][j] + " ");
}
System.out.println();
}
}
}
Consider Matrix.java and Main.java as follows.
public class Matrix extends Thread {
private static int[][] a;
private static int[][] b;
private static int[][] c;
/* You might need other variables as well */
private int i;
private int j;
private int z1;
private int s;
private int k;
public Matrix(int[][] A, final int[][] B, final int[][] C, int i, int j, int z1) { // need to change this, might
// need some information
a = A;
b = B;
c = C;
this.i = i;
this.j = j;
this.z1 = z1; // a[0].length
}
public void run() {
synchronized (c) {
// 3. How to allocate work for each thread (recall it is the run function which
// all the threads execute)
// Here this code implements the allocated work for perticular thread
// Each element of the resulting matrix will generate by a perticular thread
for (s = 0, k = 0; k < z1; k++)
s += a[i][k] * b[k][j];
c[i][j] = s;
}
}
public static int[][] returnC() {
return c;
}
public static int[][] multiply(final int[][] a, final int[][] b) {
/*
* check if multipication can be done, if not return null allocate required
* memory return a * b
*/
final int x = a.length;
final int y = b[0].length;
final int z1 = a[0].length;
final int z2 = b.length;
if (z1 != z2) {
System.out.println("Cannnot multiply");
return null;
}
final int[][] c = new int[x][y];
int i, j;
// 1. How to use threads to parallelize the operation?
// Every element in the resulting matrix will be determined by a different
// thread
// 2. How may threads to use?
// x * y threads are used to generate the result.
for (i = 0; i < x; i++)
for (j = 0; j < y; j++) {
try {
Matrix temp_thread = new Matrix(a, b, c, i, j, z1);
temp_thread.start();
// 4. How to synchronize?
// synchronized() is used with join() to guarantee that the perticular thread
// will be accessed first
temp_thread.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
return Matrix.returnC();
}
}
You can use Main.java to give 2 matrices that need to be multiplied.
class Main {
public static int[][] a = {
{1, 1, 1},
{1, 1, 1},
{1, 1, 1}};
public static int[][] b = {
{1},
{1},
{1}};
public static void print_matrix(int[][] a) {
for (int i = 0; i < a.length; i++) {
for (int j = 0; j < a[i].length; j++)
System.out.print(a[i][j] + " ");
System.out.println();
}
}
public static void main(String[] args) {
int[][] x = Matrix.multiply(a, b);
print_matrix(x); // see if the multipication is correct
}
}
In simple terms, what you all need to do is,
1) Create n (no of cells in resultant matrix) threads. Assign their roles. (Ex: Consider M X N, where M and N are matrices. 'thread1' is responsible for the multiplication of M's row_1 elements with N's column_1 elements and storing the result. This is the value for the resultant matrix's cell_1.)
2) Start each thread's process. (by start() method)
3) Wait until all the threads finish their processes and store the resultant value of each cell. Because those processes should be finished before displaying the resultant matrix. (You can do this by join() methods, and other possibilities too)
4) Now, you can display the resultant matrix.
Note:
1) Since, in this example, the shared resources (M and N) are only used to read only purpose, you don't need to use 'synchronized' methods to access them.
2) You can see, in this program, there are a group of threads running and all of them needs to achieve a specific status by their own, before continuing the next step of the whole program. This multi-threaded programming model is known as a Barrier.
Tried below code in eclipse as per thread for each cell. It works fine, you can check it.
class ResMatrix {
static int[][] arrres = new int[2][2];
}
class Matrix {
int[][] arr = new int[2][2];
void setV(int v) {
//int tmp = v;
for (int i = 0; i < 2; i++) {
for (int j = 0; j < 2; j++) {
arr[i][j] = v;
v = v + 1;
}
}
}
int[][] getV() {
return arr;
}
}
class Mul extends Thread {
public int row;
public int col;
Matrix m;
Matrix m1;
Mul(int row, int col, Matrix m, Matrix m1) {
this.row = row;
this.col = col;
this.m = m;
this.m1 = m1;
}
public void run() {
//System.out.println("Started Thread: " + Thread.currentThread().getName());
int tmp = 0;
for (int i = 0; i < 2; i++) {
tmp = tmp + this.m.getV()[row][i] * this.m1.getV()[i][col];
}
ResMatrix.arrres[row][col] = tmp;
System.out.println("Started Thread END: " + Thread.currentThread().getName());
}
}
public class Test {
//static int[][] arrres =new int[2][2];
public static void main(String[] args) throws InterruptedException {
Matrix mm = new Matrix();
mm.setV(1);
Matrix mm1 = new Matrix();
mm1.setV(2);
for (int i = 0; i < 2; i++) {
for (int j = 0; j < 2; j++) {
Mul mul = new Mul(i, j, mm, mm1);
mul.start();
// mul.join();
}
}
for (int i = 0; i < 2; i++) {
for (int j = 0; j < 2; j++) {
System.out.println("VALUE: " + ResMatrix.arrres[i][j]);
}
}
}
}
In my solution I assigned to each worker a number of rows numRowForThread equals to: (number of rows of matA) / (number of threads).
public class MatMulConcur {
private final static int NUM_OF_THREAD = 1;
private static Mat matC;
public static Mat matmul(Mat matA, Mat matB) {
matC = new Mat(matA.getNRows(), matB.getNColumns());
return mul(matA, matB);
}
private static Mat mul(Mat matA, Mat matB) {
int numRowForThread;
int numRowA = matA.getNRows();
int startRow = 0;
Worker[] myWorker = new Worker[NUM_OF_THREAD];
for (int j = 0; j < NUM_OF_THREAD; j++) {
if (j < NUM_OF_THREAD - 1) {
numRowForThread = (numRowA / NUM_OF_THREAD);
} else {
numRowForThread = (numRowA / NUM_OF_THREAD) + (numRowA % NUM_OF_THREAD);
}
myWorker[j] = new Worker(startRow, startRow + numRowForThread, matA, matB);
myWorker[j].start();
startRow += numRowForThread;
}
for (Worker worker : myWorker) {
try {
worker.join();
} catch (InterruptedException e) {
}
}
return matC;
}
private static class Worker extends Thread {
private int startRow, stopRow;
private Mat matA, matB;
public Worker(int startRow, int stopRow, Mat matA, Mat matB) {
super();
this.startRow = startRow;
this.stopRow = stopRow;
this.matA = matA;
this.matB = matB;
}
#Override
public void run() {
for (int i = startRow; i < stopRow; i++) {
for (int j = 0; j < matB.getNColumns(); j++) {
double sum = 0;
for (int k = 0; k < matA.getNColumns(); k++) {
sum += matA.get(i, k) * matB.get(k, j);
}
matC.set(i, j, sum);
}
}
}
}
}
where for the class Mat, I used this implementation:
public class Mat {
private double[][] mat;
public Mat(int n, int m) {
mat = new double[n][m];
}
public void set(int i, int j, double v) {
mat[i][j] = v;
}
public double get(int i, int j) {
return mat[i][j];
}
public int getNRows() {
return mat.length;
}
public int getNColumns() {
return mat[0].length;
}
}
I have made this program using array concept in java. I am getting Exception as ArrayIndexOutOfBound while trying to generate product.
I made the function generateFNos(int max) to generate factors of the given number. For example a number 6 will have factors 1,2,3,6. Now,i tried to combine the first and the last digit so that the product becomes equal to 6.
I have not used the logic of finding the smallest number in that array right now. I will do it later.
Question is Why i am getting Exception as ArrayIndexOutOfBound? [i couldn't figure out]
Below is my code
public class SmallestNoProduct {
public static void generateFNos(int max) {
int ar[] = new int[max];
int k = 0;
for (int i = 1; i <= max; i++) {
if (max % i == 0) {
ar[k] = i;
k++;
}
}
smallestNoProduct(ar);
}
public static void smallestNoProduct(int x[]) {
int j[] = new int[x.length];
int p = x.length;
for (int d = 0; d < p / 2;) {
String t = x[d++] + "" + x[p--];
int i = Integer.parseInt(t);
j[d] = i;
}
for (int u = 0; u < j.length; u++) {
System.out.println(j[u]);
}
}
public static void main(String s[]) {
generateFNos(6);
}
}
****OutputShown****
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 6
at SmallestNoProduct.smallestNoProduct(SmallestNoProduct.java:36)
at SmallestNoProduct.generateFNos(SmallestNoProduct.java:27)
at SmallestNoProduct.main(SmallestNoProduct.java:52)
#Edit
The improved Code using array only.
public class SmallestNoProduct {
public static void generateFNos(int max) {
int s = 0;
int ar[] = new int[max];
int k = 0;
for (int i = 1; i <= max; i++) {
if (max % i == 0) {
ar[k] = i;
k++;
s++;
}
}
for (int g = 0; g < s; g++) {
System.out.println(ar[g]);
}
smallestNoProduct(ar, s);
}
public static void smallestNoProduct(int x[], int s) {
int j[] = new int[x.length];
int p = s - 1;
for (int d = 0; d < p;) {
String t = x[d++] + "" + x[p--];
System.out.println(t);
int i = Integer.parseInt(t);
j[d] = i;
}
/*for (int u = 0; u < j.length; u++) {
System.out.println(j[u]);
}*/
}
public static void main(String s[]) {
generateFNos(6);
}
}
Maybe it better:
public class SmallestNoProduct {
public static int smallest(int n) {
int small = n*n;
for(int i = 1; i < Math.sqrt(n); i++) {
if(n%i == 0) {
int temp = Integer.parseInt(""+i+""+n/i);
int temp2 = Integer.parseInt(""+n/i+""+i);
temp = temp2 < temp? temp2: temp;
if(temp < small) {
small = temp;
}
}
}
return small;
}
public static void main(String[] args) {
System.out.println(smallest(6)); //6
System.out.println(smallest(10)); //25
System.out.println(smallest(100)); //205
}
}
Problem lies in this line
String t=x[d++]+""+x[p--];
x[p--] will try to fetch 7th position value, as p is length of array x i.e. 6 which results in ArrayIndexOutOfBound exception. Array index starts from 0, so max position is 5 and not 6.
You can refer this question regarding postfix expression.
Note: I haven't checked your logic, this answer is only to point out the cause of exception.
We are unnecessarily using array here...
below method should work....
public int getSmallerMultiplier(int n)
{
if(n >0 && n <10) // if n is 6
return (1*10+n); // it will be always (1*10+6) - we cannot find smallest number than this
else
{
int number =10;
while(true)
{
//loop throuogh the digits of n and check for their multiplication
number++;
}
}
}
int num = n;
for(i=9;i>1;i--)
{
while(n%d==0)
{
n=n/d;
arr[i++] = d;
}
}
if(num<=9)
arr[i++] = 1;
//printing array in reverse order;
for(j=i-1;j>=0;j--)
system.out.println(arr[j]);
I am trying to solve a problem by fetching the maximum number from each row in a triangle. So far am able to generate a triangle but how do I fetch the max number from each row?
Here is my code
private static Integer solve(Triangle triangle)
{
//triangle is extending an ArrayList
System.out.println(triangle);
return 0;
}
This is what am producing so far:
6
3 5
9 7 1
4 6 8 4
but now I want to get the result which says:
"In this triangle the maximum total is: 6 + 5 + 9 + 8 = 26"
Here is the complete code:
public class HellTriangle {
private static final int TRIANGLE_HEIGHT = 10;
public static void start() {
Triangle triangle = generateTriangle();
//System.out.println(triangle);
long start = System.currentTimeMillis();
Integer result = solve(triangle);
long end = System.currentTimeMillis();
System.out.println("Result:" + result);
System.out.println("Resolution time: " + (end - start) + "ms");
}
private static Triangle generateTriangle() {
Triangle triangle = new Triangle();
Random random = new Random();
for (int i = 0; i < TRIANGLE_HEIGHT; i++) {
Row row = new Row();
for (int j = 0; j <= i; j++) {
row.add(random.nextInt(100));
}
triangle.add(row);
}
return triangle;
}
private static class Row extends ArrayList<Integer> {
public String toString() {
StringBuilder sb = new StringBuilder();
for (int i = 0; i < size(); i++) {
sb.append(String.format("%02d", get(i)));
//rows.add(get(i));
if (i < (size() - 1)) {
sb.append(" ");
}
}
return sb.toString();
}
}
private static class Triangle extends ArrayList<Row> {
public String toString() {
// sb is used to make modification to the String
StringBuilder sb = new StringBuilder();
for (int i = 0; i < size(); i++) {
for (int j = 0; j < (TRIANGLE_HEIGHT - 1 - i); j++) {
sb.append(" ");
}
sb.append(get(i));
if (i < (size() - 1)) {
sb.append("\n");
}
}
return sb.toString();
}
}
private static Integer solve(Triangle triangle) {
System.out.println(triangle);
return 0;
}
public static void main(String[] args) {
start();
}
}
Any help would be appreciated!
Here, just change with your solve()
private static void solve(Triangle triangle) {
System.out.println(triangle);
ArrayList<Integer> result = new ArrayList<Integer>();
int total = 0;
for(Row row : triangle){
Collections.sort(row);
total += row.get(row.size()-1);
result.add(row.get(row.size()-1));
}
for(Integer intr : result)
System.out.println("Largest elements of the rows: " + intr);
System.out.println("Total: " + total);
}
As there is no ordering in your rows and this would lead to O(n) to get the maximum value per row i would look up the maximum value during insertion. Something like that (not tested and you probably have to override the other add methods also, depending on your use case):
public class Row extends ArrayList<Integer> {
public String toString() {
...
}
private Integer max = null;
#Override
public boolean add(Integer elem) {
if (elem != null && (max == null || max < elem)) {
max = elem;
}
return super.add(elem);
}
public Integer getMax() {
return max;
}
}
Try
private static int getTriangleMax(final Triangle rows)
{
int max = 0;
for (final Row row : rows)
{
final int rowMax = getRowMax(row);
max += rowMax;
}
return max;
}
private static int getRowMax(final Row row)
{
int rowMax = Integer.MIN_VALUE;
for (final Integer integer : row)
{
if (rowMax < integer)
{
rowMax = integer;
}
}
return rowMax;
}
Simple-Solution:
1.Add the static list as here:
private static List maxRowVal=new ArrayList();
2.Replace your generateTriangle() function with this:
private static Triangle generateTriangle()
{
Triangle triangle = new Triangle();
Random random = new Random();
for (int i = 0; i < TRIANGLE_HEIGHT; i++) {
Row row = new Row();
int maxTemp=0;
for (int j = 0; j <= i; j++) {
int rand=random.nextInt(100);
row.add(rand);
if(rand>maxTemp)
maxTemp=rand; //will get max value for the row
}
maxRowVal.add(maxTemp);
triangle.add(row);
}
return triangle;
}
Simple indeed!!
This is not exactly what you asked for, but I would like to show you a different way to go about this problem. People have done this for me before, and I really appreciated seeing different ways to solve a problems. Good luck with your coding!
Below is the code in its entirety, so you can just copy, paste and run it.
public class SSCCE {
public static void main(String[] args) {
// Here you specify the size of your triangle. Change the number dim to
// whatever you want. The triangle will be represented by a 2d-array.
final int dim = 5;
int[][] triangle = new int[dim][dim];
// Walks through the triangle and fills it with random numbers from 1-9.
for (int r = 0; r < dim; r++) {
for (int c = 0; c < r + 1; c++) {
triangle[r][c] = (int) (9 * Math.random()) + 1;
}
}
// This piece just prints the triangle so you can see what's in it.
for (int r = 0; r < dim; r++) {
for (int c = 0; c < r + 1; c++) {
System.out.print(triangle[r][c] + " ");
}
System.out.println();
}
// This part finds the maximum of each row. It prints each rows maximum
// as well as the sum of all the maximums at the end.
int sum = 0;
System.out.print("\nIn this triangle the maximum total is: ");
for (int r = 0; r < dim; r++) {
int currentMax = 0;
for (int c = 0; c < r + 1; c++) {
if (triangle[r][c] > currentMax) {
currentMax = triangle[r][c];
}
}
sum += currentMax;
if (r != 0) {
System.out.print(" + ");
}
System.out.print(currentMax);
}
System.out.println(" = " + sum + ".");
}
}
Output:
9
9 2
1 7 3
1 7 3 3
5 7 5 1 9
In this triangle the maximum total is: 9 + 9 + 7 + 7 + 9 = 41.
public class DoubleMatrix
{
private double[][] doubMatrix;
public DoubleMatrix(int row, int col)
{
if(row > 0 && col > 0)
{
makeDoubMatrix(row,col);
}
else
{
row = 1;
col = 1;
}
}
public DoubleMatrix(double[][] tempArray)
{
if(tempArray != null)
{
for(int i = 0; i < tempArray.length-1;i++)
{
if(tempArray[i].length == tempArray[i+1].length)
{
tempArray = doubMatrix;
}
}
}
else
{
makeDoubMatrix(1,1);
}
}
public int getDim1()
{
return doubMatrix.length;
}
public int getDim2()
{
return doubMatrix[0].length;
}
private void makeDoubMatrix(int row, int col)
{
double[][] tempArray = new double[row][col];
for (int i = 0;i < row;i++)
{
for(int j = 0;j < col;j++)
{
tempArray[i][j] = Math.random() * (100);
doubMatrix[i][j] = tempArray[i][j];
}
}
}
public DoubleMatrix addMatrix(DoubleMatrix secondMatrix)
{
//this. doubMatrix = doubMatrix;
double[][] tempArray;
if(secondMatrix.doubMatrix.length == doubMatrix.length)
if(secondMatrix.doubMatrix[0].length == doubMatrix[0].length)
{
tempArray = new double[doubMatrix.length][doubMatrix[0].length];
for(int i = 0; i< secondMatrix.doubMatrix.length;i++)
for(int j = 0; j< secondMatrix.doubMatrix[i].length;j++ )
{
tempArray[i][j] = secondMatrix.doubMatrix[i][j] + doubMatrix[i][j];// add two matrices
}//end for
return new DoubleMatrix (tempArray);
}
return new DoubleMatrix(1,1);
}
public DoubleMatrix getTransposedMatrix()
{
double[][] tempArray = new double[doubMatrix.length][doubMatrix[0].length];
for(int i = 0;i < doubMatrix.length;i++)
for(int j = 0;j < doubMatrix[i].length;j++)
{
tempArray[j][i] = doubMatrix[i][j];// transposed matrix2
}//end for
return new DoubleMatrix(tempArray);
}
public DoubleMatrix multiplyingMatrix(DoubleMatrix secondMatrix)
{
double[][] tempArray = new double[secondMatrix.doubMatrix.length][doubMatrix[0].length];
//check if dimension of matrix1 equal to dimension of matrix2
if(secondMatrix.doubMatrix[0].length == doubMatrix.length)
if(doubMatrix.length == secondMatrix.doubMatrix[0].length)
{
for (int i = 0; i <secondMatrix.doubMatrix.length; i++)
{
for(int j = 0; j < doubMatrix[0].length; j++)
{
for (int k = 0; k < doubMatrix.length; k++)
{
tempArray[i][j] = tempArray[i][j] + secondMatrix.doubMatrix[i][k]*doubMatrix[k][j]; // multiply 2 matrices
}
}
}//end for
}// end if
return new DoubleMatrix(1,1);
}
public void printMatrix(String text)
{
System.out.println(text);// output string
for(int i = 0; i< doubMatrix.length;i++)
{
for(int j = 0; j< doubMatrix[i].length;j++ ) {
System.out.printf("%9.1f", doubMatrix[i][j]);// out put value for matrices
}
System.out.println();
}
}
}
public class Program3
{
public static void main(String[] args)
{
int num1 = (int) (Math.random()*(10-3+1)+3);
int num2 = (int) (Math.random()*(10-3+1)+3);
DoubleMatrix doubMatObj1 = new DoubleMatrix(num1,num2);
DoubleMatrix doubMatObj2 = new DoubleMatrix(doubMatObj1.getDim1(),doubMatObj1.getDim2());
DoubleMatrix doubMatObj3;
doubMatObj2.getDim1();
doubMatObj3 = doubMatObj1.addMatrix(doubMatObj2);
doubMatObj1.printMatrix("First Matrix Object");
doubMatObj2.printMatrix("Second Matrix Object");
doubMatObj3.printMatrix("Result of Adding Matrix Objects");
doubMatObj2 = doubMatObj2.getTransposedMatrix();
doubMatObj2.printMatrix("Result of inverting Matrix Object");
doubMatObj3 = doubMatObj1.multiplyingMatrix(doubMatObj2);
doubMatObj3.printMatrix("Result of Multiplying Matrix Objects");
}
}
Hi, I have a NullPointerException error in the last line statement of the makeDoubMatrix method as well the call makedoubMatrix in side if statement of the first constructor.
doubMatrix seems to be null when I already initialize it. How will I be able to fix this problem ?
You want to initialize the array, i.e.:
private double[][] doubMatrix = new double[size1][size2];
where size1 and size2 are arbitrary sizes. What you probably want is:
if(row > 0 && col > 0)
{
doubMatrix = new double[row][col];
makeDoubMatrix(row,col);
}
else
{
doubMatrix = new double[1][1];
makeDoubMatrix(1,1);
}
which initializes the array doubMatrix to a size of row*col if both row and col are greather than 0, and to 1*1 otherwise, then calls makeDoubMatrix with its initialized size (you could have this method call after the if-else, using doubMatrix.size and doubMatrix[0].size, but I think it's more readable now).
Change the second constructor (which takes a 2D array) using the same reasoning.
You're not initializing doubMatrix. The only line which assigns a value to doubMatrix is this commented out one:
//this. doubMatrix = doubMatrix;
(And that wouldn't help.)
Ask yourself where you think you're initializing it - where do you think you've got something like:
doubMatrix = new double[1][2];
... or an assignment copying a value from another array:
doubMatrix = someOtherVariable;
If you haven't got any statements assigning it a value, you aren't initializing it, so it will always have the default value of null.