How to sort a random position in an array?

I have an array of random size filled with random numbers (between 0 and 3). I need to sort a position inside it and from that position, pick up the numbers "above" and "below" from the selected position and save it to another array, making a copy.

So far I have done this but I do not know exactly how to select the "cut" position:

 public static void main(String[] args) {

        //(1) cria o array "a" e o preenche com uma sequência de números aleatórios

        Random gerador = new Random();  // tamanho do vetor com as posições do agente
        Random numeros = new Random();  // direções que o agente tomará
        Random rnd = new Random();      // posição de corte do vetor

        int aux = gerador.nextInt(11);
        int [] a = new int[aux];
        int [] v = new int[aux];



        for (int i=0; i < a.length; i++) {
            a[i]= numeros.nextInt(4);
            System.out.println("a[" + i + "]=" + a[i]);
        }
        System.out.println();

        //(2) Copia o conteúdo de "a" para "b" com o uso de laço for

        int [] b = new int[a.length];                //primeiro é preciso reservar espaço para b
        for (int i=0; i < a.length; i++) b[i]=a[i];  //agora podemos copiar


        //(3) exibe o conteúdo de "b" 
        for (int i=0; i < a.length; i++) {
            System.out.println("b[" + i + "]=" + b[i]);
            int j =0;/*
            v[j]= numeros.nextInt(b.length);
        }
            System.out.println(v);*/


            int x=0;
            int [] s = new int[x];
            x = rnd.nextInt(i);
            s[j] = x;

            System.out.println(s);
        }

PS: This is for a genetic algorithm job, so view the vector as an agent. After the cut, I will have to cross with another vector similar to itself, but with different positions.