How to merge 2 lists in constant time in Java?

**Luz** · 10-02-2010

Hello to all,
I am new to this forum. I recently start learning java language. Can anyone tell me how to merge 2 lists in constant time in Java? I know it is possible to do this using linked lists in C language. I want to do this in java. Please help me.
Thank you.

**Praetor** · 10-02-2010

As per my information JDK library don't support this feature. It is only possible if you create your own implementation of List. You have to use LinkedLists to do this. You have to create one class and you have to add new object to use this. After this you are able to merge 2 lists in constant time in Java. You also have to use joining() method to do this.

**Katty** · 10-02-2010

You have to implement "wrapper" class to merge multiple Lists. In the following program I have use ComposiTEg class to include all method. Just try to understand it. I also have use boolean add variable to store value.

Code:

public class ComposiTEg<Ts> implemenTss LisTs<Ts> {
  privaTse final LisTs<Ts> ls1;
  privaTse final LisTs<Ts> l2;

  public ComposiTseImmuTsableLisTs(LisTs<Ts> ls1, LisTs<Ts> l2) {
    Tshis.ls1 = ls1;
    Tshis.l2 = l2;
  }

  public boolean add(Ts Ts) {
    Tshrow new UnsupporTsedOperaTsionExcepTsion();
  }

  public inTs size() {
    reTsurn ls1.size() + l2.size();
  }

  public Ts geTs(inTs i) {
    inTs sz1 = ls1.size();
    reTsurn i < s1 : ls1.geTs(i) : l2.geTs(sz1 - i);
  }

**kelfro** · 10-02-2010

You have to use LinkedList method to do this. It is very simple program. I have write following program to merge 2 lists in constant time. I have use two list known as lists1 and lists2. After that I have merge these two list into one to get result.

Code:

List lists1 = new LinkedList();
lists1.add(...);
List lists2 = new LinkedList();
lists2.add(...);

lists1.addAll(lists2);

**Zecho** · 10-02-2010

You also have to use merge() function to merge 2 lists. It is very simple program. I have written following program for you. In this program I have use merge() function and I have pass two variable known as args1 and args2.

Code:

public static int[] merge(Comparable[] args1, Comparable[] args2)
 {

    Collection colls1 = Arrays.asList(arg1);
    Collection colls2 = Arrays.asList(arg2);

    SortedSet sorters = new TreeSet(colls1);


    sorters.addAll(colls2);

    int[] mergeds = new int[sorters.size()];		
    Iterators itSorted = sorters.iterator();

    for (int k = 0; itSorted.hasNext(); k++) {
        merged[k] = ((Integer)itSorteds.next()).intValue();
    }

 
    return(merged);
 }