With this example we are going to demonstrate how to copy a Collection to another Collection. In particular, we will use an ArrayList to be copied to a Vector, but the same API applies to any type of List implementation classes e.g. LinkedList etc. In short, to copy a list to another list you should:
- Create an ArrayList.
- Populate the arrayList with elements, with
add(E e)API method of ArrayList. - Create a new Vector.
- Populate the vector with elements, with the
add(E e)API method of the Vector. - Invoke the
copy(List dstList, List sourceList)API method of the Collections. It copies all elements of the source list to the destination list, overriding any element of the destination list that resides at the same index position as the one from the source list. The destination list must be long enough to hold all copied elements of the source list otherwise IndexOutOfBoundsException is thrown.
Let’s take a look at the code snippet that follows:
package com.javacodegeeks.snippets.core;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Vector;
public class CopyListToList {
public static void main(String[] args) {
/*
Please note that the same API applies to any type of
List implementation classes e.g. LinkedList etc
*/
// Create an ArrayList and populate it with elements
ArrayList arrayList = new ArrayList();
arrayList.add("arl_element_1");
arrayList.add("arl_element_4");
arrayList.add("arl_element_2");
arrayList.add("arl_element_5");
arrayList.add("arl_element_3");
// Create a Vector and populate it with elements
Vector vector = new Vector();
vector.add("vec_element_1");
vector.add("vec_element_6");
vector.add("vec_element_7");
vector.add("vec_element_4");
vector.add("vec_element_2");
vector.add("vec_element_5");
vector.add("vec_element_3");
System.out.println("Vector Contains : " + vector);
/*
static void copy(List dstList, List sourceList) method copies all elements
of source list to destination list overriding any element of the destination
list that resides at the same index position as the one from the source list.
The destination list must be long enough to hold all copied elements of the
source list otherwise IndexOutOfBoundsException is thrown
*/
Collections.copy(vector,arrayList);
System.out.println("Vector elements after copy : " + vector);
}
}
Output:
Vector Contains : [vec_element_1, vec_element_6, vec_element_7, vec_element_4, vec_element_2, vec_element_5, vec_element_3]
Vector elements after copy : [arl_element_1, arl_element_4, arl_element_2, arl_element_5, arl_element_3, vec_element_5, vec_element_3]
This was an example of how to copy a Collection to another Collection in Java.
