ใครพอรู้วิธี random switch case แล้วไม่ซ้ำค่าเดิมบ้างครับ

คือผมอยากจะทำการ  random switch case แล้วไม่ซ้ำค่าเดิม มีวิธีไหนบ้างครับ

ตัวอย่างงาน

switch (myModel.getIntButton()) {
                        case 2:
                            imvIshihara.setImageResource(R.drawable.ishihara_02);
                            strChoice = getResources().getStringArray(R.array.time2);
                            setArray();
                            break;
                        case 3:
                            imvIshihara.setImageResource(R.drawable.ishihara_03);
                            strChoice = getResources().getStringArray(R.array.time3);
                            setArray();
                            break;
                        case 4:
                            imvIshihara.setImageResource(R.drawable.ishihara_04);
                            strChoice = getResources().getStringArray(R.array.time4);
                            setArray();
                            break;
                        case 5:
                            imvIshihara.setImageResource(R.drawable.ishihara_05);
                            strChoice = getResources().getStringArray(R.array.time5);
                            setArray();
                            break;
                        case 6:
                            imvIshihara.setImageResource(R.drawable.ishihara_06);
                            strChoice = getResources().getStringArray(R.array.time6);
                            setArray();
                            break;