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Array Method issue

having a problem with my java program. I am a newbie to Java and just can't figure out what is exactly the issue with it. In short I've declared an array and a variable in main, I've created my method call and would like my array be passed into my method with the variable. I would then like the method to take my array and count the number of times my variable "8" occurs, get rid of the 8 out of the array and return a new smaller array back to main. Here is my code below. I feel as if I am just missing one block code any suggestions?
public class Harrison7b
{
public static void main(String [] args)
{
int[] arrayA = {2,4,8,19,32,17,17,18,25,17,8,3,4,8};
int varB = 8;
// Call with the array and variable you need to find.
int[] result = newSmallerArray(arrayA, varB);
for(int x = 0; x < arrayA.length; x++)
{
System.out.print(arrayA[x] + " ");
}
}
public static int[] newSmallerArray( int[] arrayA, int varB)
{
int count = 0;
for(int x = 0; x < arrayA.length; x++)
{
if(arrayA[x] == varB)
{
count++;
}
}
int [] arrayX = new int[arrayA.length - count];
for(int B = 0; B < arrayA.length; B++)
{
if(arrayA[B] != varB)
{
}
}
return arrayX;
}
}

you do not actually need to return the array because when you pass an array to a method you also pass its memory address meaning its the same address that you change so, it will also change the arraysA of main method because you are just changing the values of the same memory adress
import java.util.*;
public class Help
{
public static void main(String[] args)
{
ArrayList<Integer> arraysA = new ArrayList<Integer>();
arraysA.add(Integer.valueOf(2));
arraysA.add(Integer.valueOf(4));
arraysA.add(Integer.valueOf(8));
arraysA.add(Integer.valueOf(19));
arraysA.add(Integer.valueOf(32));
arraysA.add(Integer.valueOf(17));
arraysA.add(Integer.valueOf(17));
arraysA.add(Integer.valueOf(18));
arraysA.add(Integer.valueOf(25));
arraysA.add(Integer.valueOf(17));
arraysA.add(Integer.valueOf(8));
arraysA.add(Integer.valueOf(3));
arraysA.add(Integer.valueOf(4));
arraysA.add(Integer.valueOf(8));
int varB=8;
newSmallerArray(arraysA,varB);
for(Integer i:arraysA)
{
System.out.println(i);
}
}
public static void newSmallerArray(ArrayList<Integer> arraysA,int varB)
{
for(int i=0;i<arraysA.size();++i)
{
if(Integer.valueOf(arraysA.get(i))==varB)
{
arraysA.remove(i);
}
}
}
}

Try this code it will not require for loop:
List<Integer> list = new ArrayList<Integer>(Arrays.asList(arrayA));
list.removeAll(Arrays.asList(8));
arrayA = list.toArray(array);

NullPointerException in Multithreaded Java code

I am trying to run the program, but it throws an exception, which I am not able to fix.
public class Multithread extends Thread {
static int [][]array1;
static int [][]array2;
static int [][]array3;
static final int i=10;
static final int j=10;
static final int k=10;
volatile int start;
volatile int end;
Multithread(int start,int end){
this.start=start;
this.end=end;
}
private static void multiplication() {
int processors=Runtime.getRuntime().availableProcessors();
int threadcount=processors>=i ? i:processors;
Thread [] t=new Thread[threadcount];
int [] idx= new int[threadcount+1];
for(int a=0;a<=threadcount;a++){
idx[a]=(a*i)/threadcount;
//System.out.println("idx:"+idx[a]);
}
for(int a=0;a<threadcount;a++){
t[a]=new Multithread(idx[a],idx[a+1]);
//thread 1=start 0 end 9, thread 2 = 9 end =19
t[a].start();
}
}
public static void main(String[] args) {
for(int a = 0; a < i; a++)
for(int b = 0; b < j; b++)
array1[a][b]= (int)(Math.random()*10);
for(int a=0;a<j;a++)
for(int b=0;b<k;b++)
array2[a][b]= (int)(Math.random()*10);
long starttime=System.nanoTime();
multiplication();
long endtime=System.nanoTime();
System.out.println("Total time taken is "+((endtime-starttime)/1000));
}
public void run(){
for(int a=start;a<end;a++){
for(int b=0;b<k;b++){
for(int c=0;c<j;c++){
array3[a][b]=(array3[a][b]+(array1[a][c]*array2[c][b]));
}
}
}
}
}
This code will give the execution time for the matrix in parallel programming. It gives me NullPointerException. I can't fix that. it gives the exception for the array1[a][b]. I tried resolving it, but could not.

You don't properly initialize your variables. Just initialize your 2d array to something, so you can later just pass reference.
array1 = blah blah //this is right
array1[a][b] //you are creating it like this everytime which is wrong.

Initialization of class array

class max{
public int buy;
public int sell;
public max(int n){
buy=0;
sell=0;
}
}
public class MaxProfit{
public void stock(int a[],int n){
max[] sol=new max[n/2+1];
if(n==1||n==0)
{
return;
}
int i=0,count=0;
while(i<n-1){
while((i<n-1)&&(a[i+1]<=a[i]))
i++;
if(i==n-1)
break;
//System.out.println(sol[count].buy=i++);
sol[count].buy=i++;
i++;
while((i<n)&&(a[i]>=a[i-1]))
i++;
sol[count].sell=i-1;
count++;
}
for(int k=0;k<count;k++)
System.out.println(sol[k].buy +sol[k].sell);
}
public static void main(String []args){
MaxProfit f=new MaxProfit();
int arr[]={20,100,260};
f.stock(arr,arr.length);
System.out.println("Hello World");
}
}
A Exception is coming which is exception in thread "main" java.lang.NullPointerException
at MaxProfit.stock(MaxProfit.java:15)
at MaxProfit.main(MaxProfit.java:32)
I am not able to solve this I have initialized array of max still I am getting null pointer exception Please help

You should initialize the elements of max[] sol maybe in a loop.
for(int i=0;i<sol.length;i++){
sol[i]=new max(aValue);
}

You are declaring an array (sol) but you are not filling your array with objects max. before using your array fill it first. Just add this to initialize your array:
max[] sol=new max[n/2+1];
for(int i = 0; i < sol.length; i++) {
sol[i] = new max(i /* or whatever the value that must be here */);
}

max[] sol=new max[n/2+1];
just defines and array with no (null) contents. You must put valid max objects in it. Like
max[i] = new max(/*param*/);
sol[count].buy=i++;
is throwing the NPE

public void stock(int a[],int n){
max[] sol=new max[n/2+1];
if(n==1||n==0)
{
return;
}
for (int k = 0; k < sol.length; k++) {
sol[k]= new max(k);
}
int i=0,count=0;
while(i<n-1){

Java - Error Message Help

In the Code, mem is a of Class Memory and getMDR and getMAR ruturn ints. When I try to compile the code I get the following errors.....how can I fix this?
Computer.java:25: write(int,int) in Memory cannot be applied to (int)
Input.getInt(mem.write(cpu.getMDR()));
^
Computer.java:28: write(int,int) in Memory cannot be applied to (int)
mem.write(cpu.getMAR());
Here is the code for Computer:
class Computer{
private Cpu cpu;
private Input in;
private OutPut out;
private Memory mem;
public Computer()
{
Memory mem = new Memory(100);
Input in = new Input();
OutPut out = new OutPut();
Cpu cpu = new Cpu();
System.out.println(in.getInt());
}
public void run()
{
cpu.reset();
cpu.setMDR(mem.read(cpu.getMAR()));
cpu.fetch2();
while (!cpu.stop())
{
cpu.decode();
if (cpu.OutFlag())
OutPut.display(mem.read(cpu.getMAR()));
if (cpu.InFlag())
Input.getInt(mem.write(cpu.getMDR()));
if (cpu.StoreFlag())
{
mem.write(cpu.getMAR());
cpu.getMDR();
}
else
{
cpu.setMDR(mem.read(cpu.getMAR()));
cpu.execute();
cpu.fetch();
cpu.setMDR(mem.read(cpu.getMAR()));
cpu.fetch2();
}
}
}
Here is the code for Memory:
class Memory{
private MemEl[] memArray;
private int size;
public Memory(int s)
{size = s;
memArray = new MemEl[s];
for(int i = 0; i < s; i++)
memArray[i] = new MemEl();
}
public void write (int loc, int val)
{if (loc >=0 && loc < size)
memArray[loc].write(val);
else
System.out.println("Index Not in Domain");
}
public int read (int loc)
{return memArray[loc].read();
}
public void dump()
{
for(int i = 0; i < size; i++)
if(i%1 == 0)
System.out.println(memArray[i].read());
else
System.out.print(memArray[i].read());
}
}
Here is the code for getMAR and getMDR:
public int getMAR()
{
return ir.getOpcode();
}
public int getMDR()
{
return mdr.read();
}

Your Memory class has a method write(int, int).
You call it with a single int. As if it was write(int).
Java complains about that: "Computer.java:28: write(int,int) in Memory cannot be applied to (int)". So either you are missing your location (loc) parameter or your value (val) parameter; depending on what code is supposed to be actually doing.

Beginner: Assigning values to arrays in Java

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));
}
}