Randomly split arraylist of uri by percentage java

>How to randomly split ArrayList<Uri> into two parts by the percentage of 70% and 30%?

After picking images from the device,i want to split this list of uri into two parts by the percentage of 70 and 30 randomly .

ArrayList<Uri> imageList = new ArrayList<>();

choose.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(Intent.ACTION_GET_CONTENT);
            intent.setType("image/*");
            intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
            startActivityForResult(intent, PICK_IMAGE);
        }
    });

@Override
protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if (requestCode == PICK_IMAGE) {

        if (resultCode == RESULT_OK) {

            assert data != null;
            if (data.getClipData() != null) {

                int countClipData = data.getClipData().getItemCount();
                int currentImageSelect = 0;

                while (currentImageSelect < countClipData) {

                    imageUri = data.getClipData().getItemAt(currentImageSelect).getUri();

                    imageList.add(imageUri);

                    currentImageSelect = currentImageSelect + 1;

                }

                alert.setText("You have selected " + imageList.size() + " Images");

            } else {
                Toast.makeText(this, "Select multiple images", Toast.LENGTH_SHORT).show();
            }

        }
    }

}

Collections.shuffle() can bring us the randomness. So do it like the following:

List<Uri> list = new ArrayList<>(imageList);
int pivot = (int) (list.size() * 0.3);

List<Uri> thirtyPercent = new ArrayList<>();
List<Uri> seventyPercent = new ArrayList<>();

Collections.shuffle(list);

for (int i = 0; i < list.size(); i++) {
    if (i <= pivot) thirtyPercent.add(list.get(i));
    else seventyPercent.add(list.get(i));
}

According to your question, you can firstly randomly shuffle the ArrayList you have and then divide and pick elements in the proportion of 70% and 30%

Here is the function to do that

public static ArrayList<ArrayList<String>> shuffleAndDivide(ArrayList<String> arrList) {
    ArrayList<ArrayList<String>> arr=new ArrayList<>();
    ArrayList<String> arr70=new ArrayList<>();
    ArrayList<String> arr30=new ArrayList<>();
    Collections.shuffle(arrList);  // Shuffle the array for randomness
    int len=arrList.size();
    int fst=(int) Math.floor(0.7*len); // Calculate the first 70% of elements
    for(int i=0; i<len; i++) { // Loop for adding them in proportions
        if(i<fst) {
            arr70.add(arrList.get(i));
        }else{
            arr30.add(arrList.get(i));
        }
    }
    // Adding them to single ArrayList
    arr.add(arr70);
    arr.add(arr30);
    return arr;
}

You just have to replace String with Uri, I write it here only for demo purpose.
You can use it like that,

ArrayList<String> mylist = new ArrayList<>();
mylist.add("Stackoverflow");
mylist.add("Java");
mylist.add("Quiz");
mylist.add("C++");
mylist.add("Practice");
mylist.add("CSharp");
mylist.add("Android");
mylist.add("Php");
mylist.add("Web");
mylist.add("Go");
ArrayList<ArrayList<String>> arrayList=shuffleAndDivide(mylist);
System.out.println("70% Array: "+arrayList.get(0));
System.out.println("30% Array: "+arrayList.get(1));