Whats the problem with this code?

Question

import javax.swing.JOptionPane;
public class change{
  int coins[] = {1,5,10,25,50};
  int change=0;
  public void backtracking(coins,change){
    int b=0;
    for(int i=0; i<=4; i++){
      if (coins[i] <= change){
        b = max(b, coins[i]+backtracking(i, change - coins));
System.out.println("Output: "+b);
public static void main(){
int input = JOptionPane.showInputDialog("Amountof the change? ");
backtracking(coins, input);

Answer 1

Here's a few, for starters
import javax.swing.JOptionPane;
public class change{
//class names should start with capital letters
  int coins[] = {1,5,10,25,50};
  int change=0;
  public void backtracking(coins,change){
//this is a method signature, needs type identifiers etc, something like public void backtracking(int[] anyIntArray,int anyInt)
    int b=0;
    for(int i=0; i<=4; i++){
//here, 4 is a magic number, if you mean <= all the elements of coins[], use < coins.length
      if (coins[i] <= change){
//coins[i] will never be less then change(which is 0)
        b = max(b, coins[i]+backtracking(i, change - coins));
//there is no method max declared anywhere
System.out.println("Output: "+b);
public static void main(){
//main method signature is incorrect, will compile, but will error
int input = JOptionPane.showInputDialog("Amountof the change? ");
//you're trying to put a string into an int
backtracking(coins, input);
//you have not created an instance of class Change, to use this method