You don't need the getters in the equals() method. Private means accessible only from that class. The catch is that separate instances are still the same class. This compiles, for example:

public class Card {

	private int value;
	private int suit;

	public Card(int value, int suit) {
		this.value = value;
		this.suit = suit;
	}

	public boolean equals(Card other) {
		return (value == other.value) && (suit == other.suit);
	}

}

That just isn't true. You can play the guitar no matter how rich or poor you are (as long as you have one to start with). Listening to music is also cheap and a lot of people do it in their homes, on their commute and at their work.

The gym can be expensive but it is something that is affordable as long as you are in gainful employment or are a student (since most universities have very cheap gyms).

Classes and travelling are more of a time issue than a money issue for most. However, I bet even the busiest people could find one evening a week, and everybody gets holidays, right?

Before you do that, be aware it will only work on Windows and if you mess it up, there is a good chance of messing up your users' computers. Java Web Start is designed to add similar functionality to Java programs. I would at least look into it before playing with the registry.

Why not use Java's collections to your advantage? A good answer might be that this is for class.

As an aside, checkArray() is a bad method name. It doesn't tell you what you are checking for and it's lying about working with arrays. hasNonZeroDuplicates() is better and I'm sure there are better still.

import java.util.*;

public class Duplicates {

	public static void main(String[] args) {
		reportResult(1, 2, 3, 4, 5);
		reportResult(0, 1, 2, 3, 4, 5, 0);
		reportResult(0, 1, 2, 3, 4, 1, 2, 5, 0);
		reportResult(1, 2, 3, 4, 1, 2, 5);
	}

	public static void reportResult(Integer... list) {
		System.out.print(Arrays.toString(list));
		String indicator = hasNonZeroDuplicates(Arrays.asList(list)) ? "has" : "does not have";
		System.out.println(" This list " + indicator + " non-zero duplicates.");
	}

	public static boolean hasNonZeroDuplicates(List<Integer> list) {
		return hasDuplicates(removeAllInstances(list, 0));
	}

	public static <T> List<T> removeAllInstances(List<T> list, T item) {
		List<T> copy = new ArrayList<>(list);
		while (copy.remove(item)) {
			// Keep going until remove() returns false.
		}
		return copy;
	}

	public static <T> boolean hasDuplicates(List<T> list) {
		Set<T> set = new HashSet<>(list);
		return list.size() != set.size();
	}

}

Quote

I think I'd run into issues with that too. My native language is English.