Example.java

import java.util.ArrayList;
class Untitled {
	public static Double[] fake_data = {2.3, 5.2, 4.5};
	public static Integer fake_rows = 5;
	public static ArrayList<ArrayList> linelist;
	
	public static void run(){
		linelist = new ArrayList<ArrayList>();
		for(int i=0; i<fake_rows; i++){
			ArrayList<Double> row = new ArrayList<Double>(); 
			for(int j=0; j<fake_data.length; j++){
				row.add(fake_data[j]);		
			}
			linelist.add(row);
		}
		System.out.println(linelist);
		
		ArrayList<Double> row = linelist.get(0);
		for(Double point: row){
			// Do things with the point
		}
		for(Double point: linelist.get(0)){
			// Do things with the point
		}
	}
	public static void main(String[] args) {
		run();
	}
}

Untitled 2.java:22: error: incompatible types
        for(Double point: linelist.get(0)){
                                      ^
  required: Double
  found:    Object