Java, find intersection in integer list

Question

I have an object ArrayList like:

{{"ObjectName",[[1,3],[11,24]]},
{"ObjectName2",[[3,4],[5,6],[12,20]]},
{"ObjectName3",[[30,38]]}}

The object is formed by a string(object name) and many pairs of integer list inside a integer list.

A pair of integer list like [11,24]: means from 11cm to 24cm, a length range.

How could I use Java code and less bigO to check if the pairs of length of 1 object has an intersection with other objects' length range. Like ObjectName2 has a pair of integer [12,20] is intersect with ObjectName's [11,24].

I have a sudo code has bigO(n^3):

for(Object o1 : Arraylist){
   for(Object o2 : Arraylist){
       for(int x = 0; x < o1.lengthlist.size(),x++){

            if(o1.lengthlist.get(x)[0]>=o2.lengthlist.get(x)[0]
                && o1.lengthlist.get(x)[1]<=o2.lengthlist.get(x)[1])
               {got the intersection part}
       }
    }
}

Answer 1

I did a full example of how to do it.

Class 1

package intersectioninintegerlist;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 *
 * @author Ahmad
 */
public class IntersectionInIntegerList {

    public static void main(String[] args) {
        List<Pair> lst1 = new ArrayList<>(Arrays.asList(new Pair(1,3), new Pair(11,24)));
        Obj obj1 = new Obj("obj1", lst1);

        List<Pair> lst2 = new ArrayList<>(Arrays.asList(new Pair(3,4), new Pair(5,6), new Pair(12,20)));
        Obj obj2 = new Obj("obj2", lst2);

        List<Pair> lst3 = new ArrayList<>(Arrays.asList(new Pair(30,38)));
        Obj obj3 = new Obj("obj3", lst3);

        List<Obj> objs = new ArrayList<>(Arrays.asList(obj1, obj2, obj3));

        for(int i = 0; i < objs.size(); i++){
            for(int j = i+1; j < objs.size(); j++){
                findIntersect(objs.get(i), objs.get(j));
            }
        }

    }

    private static void findIntersect(Obj o1, Obj o2) {
        System.out.println(o1.name + " - " + o2.name);
        for(Pair p1 : o1.pairs){
            for(Pair p2 : o2.pairs){
                int A = p1.i1;
                int B = p1.i2;
                int X = p2.i1;
                int Y = p2.i2;
                if((A >= X && A <= Y) || (X >= A && X <= B)){
                    System.out.println(o1.name + " intersects with " + o2.name);
                }
            }
        }
    }
}

Class2

package intersectioninintegerlist;

import java.util.List;

/**
 *
 * @author Ahmad
 */
public class Obj {

        public String name;
        public List<Pair> pairs;

        public Obj(String n, List<Pair> p){
            name = n;
            pairs = p;
        }
}

Class3

package intersectioninintegerlist;

/**
 *
 * @author Ahmad
 */
public class Pair {
        int i1;
        int i2;
        public Pair(int _i1, int _i2){
            i1 = _i1;
            i2 = _i2;
        }
}

Hope It helps.