Below is my code. Here, i have to switch two of the names in the 2D array but i'm not sure how to do this.
Anyone knows how to do?
import java.util.Scanner;
public class Homeworktest {
public static void main(String[] args) {
String[][] people = new String[3][3];
people[0][0] = "April";
people[0][1] = "Jenny";
people[0][2] = "Charlie";
people[1][0] = "Maya";
people[1][1] = "Daniel";
people[1][2] = "Felix";
people[2][0] = "Jack";
people[2][1] = "Charlotte";
people[2][2] = "Nick";
for(int i = 0; i < people.length; i++) {
String[] subarrays = seatingChart[i];
for(int y = 0; y < people.length; y++) {
System.out.print(subarrays[y] + " ");
}
System.out.println();
}
public static void switchSeats(int row1, int col1, int row2, int col2) {
}
}
}
To swap values of two array locations, first, hold one value in a temporary variable, assign the second location's value to the first location and lastly assign the temporary variable's value to the second location.
public static void switchSeats(String[][] people, int row1,
int col1, int row2, int col2) {
String tmp = people[row1][col1];
people[row1][col1] = people[row2][col2];
people[row2][col2] = tmp;
}
In the above code, tmp serves as the temporary variable.
Related
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);
I want to create a game and I need to read file from the notepad
when I use my loadfile.java alone, it work very well. Then, I would like to copy my data into datafile.java as it will be easier for me to do the fighting scene. However, I can't copy the array in my loadfile.java to the datafile.java and I don't understand why.
import javax.swing.*;
import java.io.*;
import java.util.Scanner;
public class loadfile
{
static String filename = "Save.txt";
static int size = 4;
static int s;
static int[] number;
static String[] line;
private static void load() throws IOException
{
BufferedReader reader = new BufferedReader(new FileReader(filename));
while (reader.readLine()!= null)
{
size++;
}
size -= 4;
reader.close();
line = new String[size];
number = new int[size];
BufferedReader reader2 = new BufferedReader(new FileReader(filename));
for (int i = 0; i < size; i++)
{
line[i] = reader2.readLine();
}
reader2.close();
for (int i = 4; i < size; i++)
{
number[i] = Integer.parseInt(line[i]);
}
}
public static String[] getData()
{
return line;
}
public static int[] getNumber()
{
s = size - 4;
int[] num = new int[s];
for (int i = 0; i < s; i++)
{
num[i] = number[i+4];
}
return num;
}
public static int getDataSize()
{
return size;
}
public static int getNumberSize()
{
return size - 4;
}
This is my loadfile.java
I use the file with 4 names and 9 * n int in the notepad as I want to check whether I have the character first before I read the file. However, before I can handle this problem, I got another problem that I can't copy the array into my datafile.java
The datafile.java is separate with two constructor. One is for Starting the game and one is for loading the data. The constructor with the (int num) is the problem I have. First, I would like to show the java first:
import java.util.Arrays;
import java.io.*;
public class datafile
{
private static String[] data;
private static int[] number;
private static String[] name;
private static int[] a, d, s;
private static int[] hp, maxhp;
private static int[] mp, maxmp;
private static int[] lv, exp;
public datafile()
{
initialization();
name[0] = "Pet";
a[0] = 100;
d[0] = 100;
s[0] = 100;
hp[0] = 500;
mp[0] = 500;
maxhp[0] = 500;
maxmp[0] = 500;
exp[0] = 100;
lv[0] = 1;
}
public datafile(int num) throws IOException
{
initialization();
loadfile l = new loadfile();
for (int i = 0; i < l.getNumberSize(); i++)
{
number[i] = l.getNumber()[i];
}
for (int i = 0; i < l.getDataSize(); i++)
{
data[i] = l.getData()[i];
}
for(int i = 0; i < 4; i++)
{
name[i] = data[i];
}
for(int i = 0; i < 4; i++)
{
a[i] = number[1+(i*9)];
d[i] = number[2+(i*9)];
s[i] = number[3+(i*9)];
hp[i] = number[4+(i*9)];
mp[i] = number[5+(i*9)];
maxhp[i] = number[6+(i*9)];
maxmp[i] = number[7+(i*9)];
lv[i] = number[8+(i*9)];
exp[i] = number[9+(i*9)];
}
}
public static String getName(int n)
{
return name[n];
}
public static int getAttack(int n)
{
return a[n];
}
public static int getDefense(int n)
{
return d[n];
}
public void initialization()
{
name = new String[3];
a = new int[3];
d = new int[3];
s = new int[3];
hp = new int[3];
mp = new int[3];
maxhp = new int[3];
maxmp = new int[3];
lv = new int[3];
exp = new int[3];
}
public static void main (String[] args) throws IOException
{
new datafile(1);
}
}
When I run the program, the debugging state this line
data[i] = l.getData()[i];
as an error
I don't know what wrong with this line and I tried so many different ways to change the way the copy the method. However, it didn't work
The error says this:
Exception in thread "main" java.lang.NullPointerException
at datafile.<init>(datafile.java:38)
at datafile.main(datafile.java:92)
I hope you guys can help me with this problem because I don't want to fail with my first work
in your datafile(int num)
you call
loadfile l = new loadfile();
but you never call the load() method on you loadfile
l.load();
Edit: my bad, I didn't see your initialization method, but regardless, I'm going to stick with my recommendation that you radically change your program design. Your code consists of a kludge -- you've got many strangely named static array variables as some kind of data repository, and this suggests that injecting a little object-oriented design could go a long way towards creating classes that are much easier to debug, maintain and enhance:
First I recommend that you get rid of all of the parallel arrays and instead create a class, or likely classes, to hold the fields that need to be bound together and create an ArrayList of items of this class.
For example
public class Creature {
private String name;
private int attack;
private int defense;
// constructors here
// getters and setters...
}
And elsewhere:
private List<Creature> creatureList = new ArrayList<>();
Note that the Creature class, the repository for some of your data, should not be calling or even have knowledge of the code that loads the data, but rather it should be the other way around. The class that loads data should create MyData objects that can then be placed within the myDataList ArrayList via its add(...) method.
As a side recommendation, to help us now and to help yourself in the future, please edit your code and change your variable names to conform with Java naming conventions: class names all start with an upper-case letter and method/variable names with a lower-case letter.
I am trying to add random numbers to an empty array 20 numbers 0-99. When I run the code below it prints out 51 numbers and they are all 0.
Can someone please help me figure out what I am doing wrong here.
import java.util.Random;
public class SortedArray
{
int randomValues;
int[] value;
public SortedArray()
{
}
public int getRandom()
{
Random random = new Random();
for(int j=0; j<20; j++)
{
randomValues = random.nextInt(100);
}
return randomValues;
}
public int getArray()
{
int result = 0;
value = new int[randomValues];
for(int item : value)
{
System.out.println("The array contains " + item);
}
return result;
}
}
Here is my main method
public class ReturnSortedArray
{
public static void main(String[] args)
{
SortedArray newArray = new SortedArray();
int random = newArray.getRandom();
int array = newArray.getArray();
System.out.println(array);
}
}
In your method getArray
the code
value = new int[randomValues];
is simply creating a new empty int array of size ramdomValues.
As the default value of an int is 0, that is what you are getting
Also in your method getRandom you are setting the same value time and time again
for (...)
randomValues = random.nextInt(100);
try
public int[] getRandomArr()
{
int randomValues [] = new int [20];
Random random = new Random();
for(int j=0; j<20; j++)
{
randomValues[j] = random.nextInt(100);
}
return randomValues;
}
I see a few issues, you should probably set the values in your constructor. You could also call it a set method (since it's not actually a get). Also, your getArray() doesn't return an array. So, I think you really wanted something like this,
public class SortedArray {
private Random random = new Random();
private int[] value = new int[20];
public SortedArray() {
super();
setRandomValues();
}
public void setRandomValues() {
for (int j = 0; j < value.length; j++) {
value[j] = random.nextInt(100);
}
}
public int[] getArray() {
return value;
}
}
And then your main method, should be updated like
public static void main(String[] args) {
SortedArray newArray = new SortedArray();
int[] array = newArray.getArray();
System.out.println(Arrays.toString(array));
}
My apologize, I have a class on my Project, called test01.java. And i used the library from Tadaki Graphlib contained many class. On of them is Graph.java.
Test01.java:
public class test01 extends Graph{
public test01(String name, int n) {
super(name);
public test01(String name, int n) {
super(name);
graphLib.Vertex vList[] = new graphLib.Vertex[n];
for (int i = 0; i < n; i++) {
vList[i] = new graphLib.Vertex(String.valueOf(i));
addVertex(vList[i]);
}
int deg = 0;
System.out.println("<---------- Random val ---------->");
addArc(vList[0], vList[1], String.valueOf(0)); deg++;
addArc(vList[1], vList[0], String.valueOf(1)); deg++;
System.out.println("Vertex-0 with Vertex-1");
System.out.println("Vertex-1 with Vertex-0");
int k = 2;
int l;
int m=0;
Random randomval = new Random();
int isAvailInt [] = new int[n];
while (k<n) {
for(l=0;l<k;l++){
isAvailInt [l]= Integer.parseInt(vList[l].toString());
m=isAvailInt[l];
}
int chosen = randomval.nextInt(m);
addArc(vList[k], vList[chosen], String.valueOf(k));
System.out.println("Vertex-"+k+" with Vertex-"+chosen+
" exp = " + String.valueOf(k));
k++;
}
}public static void main(String args[]) {
int n;
String num = JOptionPane.showInputDialog("Masukkan nilai jumlah iterasi = ");
String degnum = null;
n = Integer.parseInt(num);
int deg []= new int [n];
test01 t = new test01("test",n);
System.out.println("<---------- Vertex-i = Degree-i ------------>");
graphLib.Graph g= new Graph("test");
int [][]adj = g.getAdjacent();
System.out.println(adj[0][0]);
for (int i=0; i<t.getSize();i++){
for (int j=0; j<t.getSize();j++){
}
}}
and one other class called Graph.java
public class Graph extends GraphBase { int adjacent[][] = null;
public Graph(String name) {
this.name = name;
vertexes = Utils.createVertexList();
arcs = Utils.createArcList();
a2vHead = new HashMap<>();
a2vTail = new HashMap<>();
v2a = new HashMap<>();
}
public int[][] getAdjacent() {
int n = vertexes.size();
adjacent = new int[n][];
for (int i = 0; i < n; i++) {
adjacent[i] = new int[n];
for (int j = 0; j < n; j++) {
adjacent[i][j] = 0;
}
}
if (directed) {
for (int i = 0; i < n; i++) {
Vertex v = vertexes.get(i);
for (Arc a : v2a.get(v)) {
Vertex t = a2vTail.get(a);
int l = vertexes.indexOf(t);
adjacent[l][i]++;
}
}
} else {
for (int i = 0; i < n; i++) {
Vertex v = vertexes.get(i);
for (Arc a : v2a.get(v)) {
Vertex t = a2vTail.get(a);
if (!t.equals(v)) {
int l = vertexes.indexOf(t);
adjacent[i][l]++;
adjacent[l][i]++;
}
}
}
}
checkConnectedness();
return adjacent;
}}
From above, method - int [][] Adjacent() - has an array return value:
return adjacent;
Then I want to received it with array variable declared:
int [][]adj = g.getAdjacent();
But when I run the program, the code :
System.out.println(adj[0][0]);
Has appeared error :
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
I've declare the variable vertexes in Graph.java that extended from other class, GraphBase.java:
vertexes = Utils.createVertexList();
How do I obtain an array value form a variable adjacent in Graph.java to test01.java and how do I display it with System.out.println() ?
Well you haven't shown where vertexes is initialized (or even declared) in Graph. I suspect it's empty, so when you execute this code:
public int[][] getAdjacent() {
int n = vertexes.size();
adjacent = new int[n][];
...
return adjacent;
}
... you'll end up with an empty array. That would cause the problem you've seen. You can easily check the size in your main method:
System.out.println(adj.length);
I suspect you'll find it's 0. Either that, or adj[0].length is 0.
It's not clear how you expect the Graph to find any vertexes - you don't supply it with any, or even the value of n. You just call the constructor with a string:
graphLib.Graph g= new Graph("test");
Unless that's meant to be the name of a file which is loaded in the constructor, there's nowhere for it to get data from. You need to take a step back and think about where you expect the data to come from, then make sure that it can actually flow through your program. The problem isn't getting the array reference back to main - the problem is that the array is empty.
I doubted about this line returning 0.
int n = vertexes.size();
You can reproduce this issue by running below code
int adjacent[][] = new int[0][];
System.out.println(adjacent[0][0]);
You will get the same exception
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
To solve this issue
Make sure before proceeding vertexes have expected values.
I am new to programming and Java as well. I need to write a void method which sorts the array entered, I have the code written but do not know how to display the sorted list from void method. Anyone willing to help. It will be greatly appreciated.
package util.assign4;
import java.util.StringTokenizer;
import javax.swing.JOptionPane;
import util.IO;
public class UtilAssign4 {
public static int[] getData (String input){
StringTokenizer st = new StringTokenizer(input);
int []x = new int[st.countTokens()];
for(int i = 0;st.hasMoreTokens(); i++){
try{
x[i] = Integer.parseInt(st.nextToken());
}
catch(Exception e){
JOptionPane.showMessageDialog(null," Invalid input");
System.exit(1);
}
}
return x;
}
public static int getHighest(int g[]){
int hi = g[0];
for( int k = 1; k <g.length;k++)
if(g[k]> hi) hi = g[k];
return hi;
}
public static int getSmallest(int p[]){
int sm = p[0];
for(int l = 1;l<p.length;l++)
if(p[l] < sm) sm = p[l];
return sm;
}
public static float getAverage(int n[]){
float sum = 0.0f;
for(int y = 0;y <n.length; y++) sum += n[y];
return sum/n.length;
}
public static void getSorted(int grades []){
for(int i = 0; i<grades.length-1;i++){
int largest =i;
for(int j = 0;j<grades.length;j++)
if(grades[j]>grades[largest]) largest = j;
int temp = grades[largest];
grades[largest] = grades[i];
grades[i]=temp;
}
}
public static void main(String[] args) {
String input = JOptionPane.showInputDialog("Enetr one or more grades:");
int [] x = getData(input);
int j = getHighest(x);
int m = getSmallest(x);
float a = getAverage(x);
IO.showMsg("Array you entered:" + input + String.format("\nThe"
+ " higheset grade is:%2d \n"
+ "The Lowest Grade is:%2d \n"+"The average is:%2.2f\n"
+ "The sorted list: ",
j,m,a));
}
}
You are not supposed to print the contents of the array in the sort method. Your requirement (I wager) is to sort the array supplied to the method 'in-place' (which it already looks like you are doing). What this means is that given an array:
int[] grades = new int[] {34, 76, 12, 0, -1};
That when you call:
UtilAssign4.getSorted(grades);
That the array passed into the method is actually sorted inside the method, and as such does not need to be returned (that's why your return type is void). So to summarize, before calling the sort method, your array is unsorted. After the call completes, tbe very same array has now been sorted.
So now you can then print out the sorted array in the calling method (in this case main(String[]):
getSorted(x); // <-- call the sort function, on your array
String msg = String.format("\nThe higheset grade is:%2d \n"
+ "The Lowest Grade is:%2d \nThe average is:%2.2f\n"
+ "The sorted list: %s", j, m, a, Arrays.toString(x));
IO.showMsg(msg);
Note the Arrays.toString(x)? That will take your sorted array, and convert it into a string representation (will look something like this: [76, 34, 12, 0, -1]).
in void method short your array in any field Array that is
public class UtilAssign4 {
private Integer[] shorted = new Integer[100];
public static int[] getData (String input){
.
.
}
and do your stuff with above array in your void method and use this where you want