There are many algorithm available in java.util.Collections class which provides many static util methods.
All these method take one of the argument as the list or the collection where the algorithm need to be applied. Some of them are:
All these method take one of the argument as the list or the collection where the algorithm need to be applied. Some of them are:
- reverse - This static method will reverse the order of the specified list.
- swap - This static method will swap the elements at the specified positions of the list.
- shuffle - This static method will reorders all the elements in the list randomly.
- fill - This static method will fill/replace all the elements in the list with a specified value.
- replaceAll- This static method will replace all the occurrence of one specified value in the list with another value
Below sample program will illustrate how these methods can be used.
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class CollectionsSample {
public static void main(String[] args) {
CollectionsSample collectionsSample= new CollectionsSample();
collectionsSample.reverse();
collectionsSample.swap();
collectionsSample.shuffle();
collectionsSample.fill();
collectionsSample.replace();
}
private void reverse() {
List<String> list=initializeList();
System.out.println("Values in List before reverse:"+list);
Collections.reverse(list);
System.out.println("Values in List after reverse:"+list);
System.out.println();
}
private void swap() {
List<String> list=initializeList();
System.out.println("Values in List before swap:"+list);
Collections.swap(list,1,3);
System.out.println("Values in List after swap:"+list);
System.out.println();
}
private void shuffle() {
List<String> list=initializeList();
System.out.println("Values in List before shuffle:"+list);
Collections.shuffle(list);
System.out.println("Values in List after shuffle:"+list);
System.out.println();
}
private void fill() {
List<String> list=initializeList();
System.out.println("Values in List before fill:"+list);
Collections.fill(list,"NA");
System.out.println("Values in List after fill:"+list);
System.out.println();
}
private void replace() {
List<String> list=initializeList();
System.out.println("Values in List before replace:"+list);
Collections.replaceAll(list,"Tennis","TableTennis");
System.out.println("Values in List after replace:"+list);
System.out.println();
}
private List<String> initializeList()
{
List<String> list= new ArrayList<String>();
list.add("Cricket");
list.add("Footbal");
list.add("Tennis");
list.add("Baseball");
return list;
}
}
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Output:
Values in List before reverse:[Cricket, Footbal, Tennis, Baseball]
Values in List after reverse:[Baseball, Tennis, Footbal, Cricket]
Values in List before swap:[Cricket, Footbal, Tennis, Baseball]
Values in List after swap:[Cricket, Baseball, Tennis, Footbal]
Values in List before shuffle:[Cricket, Footbal, Tennis, Baseball]
Values in List after shuffle:[Tennis, Footbal, Cricket, Baseball]
Values in List before fill:[Cricket, Footbal, Tennis, Baseball]
Values in List after fill:[NA, NA, NA, NA]
Values in List before replace:[Cricket, Footbal, Tennis, Baseball]
Values in List after replace:[Cricket, Footbal, TableTennis, Baseball]
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