public static ArrayList<ArrayList<String[]>> train_test(){
		ArrayList<String[]> list = read_file.readInData("u.data", '\t');
		int size = list.size();
		int test = (int)(size * 0.3);
		int[] randselect = new int[size];
		for(int i = 0; i < randselect.length; i++)
			randselect[i] = i;
		ArrayList<Integer> testset = new ArrayList<Integer>();
		int count = size;
		while(testset.size() < test){
		    for(int i = 0; i < test; i++){
			    Random rand = new Random();
			    int value = rand.nextInt(count);
			    testset.add(randselect[value]);
			    randselect[value] = randselect[count - 1];
			    count--;
		    }
		}
		ArrayList<String[]> testlist = new ArrayList<String[]>();
		ArrayList<String[]> trainlist = new ArrayList<String[]>();
		for(int i = 0; i < list.size(); i++)
		    trainlist.add(list.get(i));
		for(int i = 0; i < testset.size(); i++){
			testlist.add(list.get(i));
			trainlist.remove(i);
		}
		ArrayList<ArrayList<String[]>> result = new ArrayList<ArrayList<String[]>>();
		result.add(trainlist);
		result.add(testlist);
		return result;
	}