Practice›Java Fundamentals›Module 10. Collections›10.2 HashSet

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10.2 HashSet — detect a duplicate

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Task

Fill in hasDuplicate so that it returns true when a value appears more than once.

Keep a set of values already seen; check before adding, otherwise every value looks like a repeat. The program prints true and then false.

Your solution

import java.util.HashSet;
import java.util.Set;

public class Main {

    public static boolean hasDuplicate(int[] arr) {
        // true if any value appears twice

    }

    public static void main(String[] args) {
        System.out.println(hasDuplicate(new int[]{1, 2, 3, 2}));
        System.out.println(hasDuplicate(new int[]{1, 2, 3}));
    }
}

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