数组的增删改查

public static void main(String[] args) {
        int[] arr = new int[]{10,20,30,22,15};

        System.out.println(Arrays.toString(arr));
       // System.out.println(Arrays.toString(insert(arr)));
       // System.out.println(Arrays.toString(insertT(arr)));
        //System.out.println(Arrays.toString(delete(arr)));
        //System.out.println(Arrays.toString(change(arr)));
        System.out.println((select(arr)));
}

private static int[] insert(int[] arr){
        Scanner scan = new Scanner(System.in);
        System.out.println("插入位置");
        int index = scan.nextInt();
        int digits = arr.length;
        if(index>=digits || index<0){
            System.out.println("越界");
        }
        System.out.println("插入的值");
        int num = scan.nextInt();
        int[] newArr = new int[arr.length+1];
        for (int i = 0; i < index; i++) {
            newArr[i] = arr[i];
        }
        newArr[index]=num;
        for (int j = index; j < arr.length; j++) {
            newArr[j+1] = arr[j];
        }
        arr = newArr;
        return arr;
}

private static int[] insertT(int[] arr){
        Scanner scan = new Scanner(System.in);
        System.out.println("插入的值");
        int num = scan.nextInt();
        int[] newArr = new int[arr.length+1];
        for (int i = 0; i < arr.length; i++) {
            newArr[i]=arr[i];
        }
        newArr[arr.length]=num;
        arr=newArr;
        return arr;
}

private static int[] delete(int[] arr){
        Scanner scan = new Scanner(System.in);
        System.out.println("删除哪一个位置的值");
        int index = scan.nextInt();
        int delight = arr.length;
        if (index>=delight || index<0){
            System.out.println("越界");
        }
        for (int i = index; i <arr.length-1; i++) {
            arr[i] = arr[i+1];
        }
        int[] newArr = new int[arr.length-1];
        for (int j = 0; j <arr.length-1 ; j++) {
            newArr[j]=arr[j];
        }
        arr = newArr;
        return arr;
}

private static int[] change(int[] arr){
        Scanner scan = new Scanner(System.in);
        System.out.println("输入改动的位置");
        int index = scan.nextInt();
        int delight=arr.length;
        if (index>=delight || index<0){
            System.err.println("越界");
        }
        System.out.println("输入改动值");
        int num = scan.nextInt();
        arr[index]=num;
        return arr;
}

private static int select(int[] arr){
        Scanner scan = new Scanner(System.in);
        System.out.println("查哪");
        int index = scan.nextInt();
        int delight = arr.length;
        if (index>=delight || index<0){
            System.err.println("越界");
        }
        int a = arr[index];
        return a;
}