2.7 intersection, Java

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//'main' method must be in a class 'Rextester'.
//Compiler version 1.8.0_111

import java.util.*;
import java.lang.*;

class Rextester
{  
    public static void main(String args[])
    {
        Node a = new Node(1);
        Node a1 = new Node(2);
        Node a2 = new Node(3);
        Node a3 = new Node(4);
        a.next = a1;
        a1.next = a2;
        a2.next = a3;
        
        Node b = new Node(1);
        b.next = a;
        
        Node intersec = intersection(a, b);
        System.out.println(intersec.val);
    }
    
    public static Node intersection(Node a, Node b)
    {
        int alen = length(a);
        int blen = length(b);
        
        if(alen<blen)
        {
            while(alen<blen)
            {
                b = b.next;
                blen--;
            }
        }
        else
        {
            while(alen>blen)
            {
                a = a.next;
                alen--;
            }
        }
        
        while(a !=null && b!=null)
        {
            if(a==b)
                return a;
            
            a=a.next;
            b=b.next;
        }
        
        return null;
    }
    
    public static int length(Node a)
    {
        int len = 0;
        while(a !=null)
        {
            a=a.next;
            len++;
        }
        
        return len;
    }
}

class Node
{
    public int val;
    public Node next;
    
    public Node(int val)
    {
        this.val = val;
    }    
}

[ + ] Show input
Compilation time: 0.62 sec, absolute running time: 0.12 sec, cpu time: 0.09 sec, memory peak: 18 Mb, absolute service time: 0,75 sec