java数组怎么去掉重复的

public int[] removeDuplicates(int[] arr) {
    Set<Integer> set = new HashSet<>();
    for (int i = 0; i < arr.length; i++) {
        set.add(arr[i]);
    }
    int[] result = new int[set.size()];
    int index = 0;
    for (int num : set) {
        result[index++] = num;
    }
    return result;
}

public int[] removeDuplicates(int[] arr) {
    if (arr.length == 0) {
        return arr;
    }
    Arrays.sort(arr);
    int i = 0, j = 1;
    while (j < arr.length) {
        if (arr[i] != arr[j]) {
            arr[++i] = arr[j];
        }
        j++;
    }
    return Arrays.copyOf(arr, i + 1);
}

public int[] removeDuplicates(int[] arr) {
    Map<Integer, Integer> map = new HashMap<>();
    for (int i = 0; i < arr.length; i++) {
        if (!map.containsKey(arr[i])) {
            map.put(arr[i], 0);
        }
        map.put(arr[i], map.get(arr[i]) + 1);
    }
    int[] result = new int[map.size()];
    int index = 0;
    for (int num : map.keySet()) {
        result[index++] = num;
    }
    return result;
}