Java Collections reverse() Method

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Description

The Java Collections reverse(List<?>) method is used to reverse the order of the elements in the specified list.

Declaration

Following is the declaration for java.util.Collections.reverse() method.

public static void reverse(List<?> list)			 

Parameters

list − This is the list whose elements are to be reversed.

Return Value

NA

Exception

UnsupportedOperationException − This is if the specified list or its list-iterator does not support the set operation.

Reversing a List of Integers Example

The following example shows the usage of Java Collection reverse(List) method. We've created a List object with some integers, printed the original list. Using reverse(List) method, we've reversed the list and printed it.

package com.tutorialspoint;

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

public class CollectionsDemo {

   public static void main(String[] args) {
      List<Integer> list = new ArrayList<>(Arrays.asList(1,2,3,4,5));

      System.out.println("Initial collection value: " + list);
      // reverse collection
      Collections.reverse(list);
      System.out.println("Final collection value: "+list);
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Initial collection value: [1, 2, 3, 4, 5]
Final collection value: [5, 4, 3, 2, 1]

Reversing a List of Strings Example

The following example shows the usage of Java Collection reverse(List) method. We've created a List object with some strings, printed the original list. Using reverse(List) method, we've reversed the list and printed it.

package com.tutorialspoint;

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

public class CollectionsDemo {

   public static void main(String[] args) {
      List<String> list = new ArrayList<>(Arrays.asList("Welcome","to","Tutorialspoint"));

      System.out.println("Initial collection value: " + list);
      // reverse this collection
      Collections.reverse(list);
      System.out.println("Final collection value: "+list);
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Initial collection value: [Welcome, to, Tutorialspoint]
Final collection value: [Tutorialspoint, to, Welcome]

Reversing a List of Objects Example

The following example shows the usage of Java Collection reverse(List) method. We've created a List object with some Student objects, printed the original list. Using reverse(List) method, we've reversed the list and printed it.

package com.tutorialspoint;

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

public class CollectionsDemo {

   public static void main(String[] args) {
      List<Student> list = new ArrayList<>(Arrays.asList(new Student(1, "Julie"),
         new Student(2, "Robert"), new Student(3, "Adam")));

      System.out.println("Initial collection value: " + list);
      // reverse this collection
      Collections.reverse(list);
      System.out.println("Final collection value: "+list);
   }
}
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Initial collection value: [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ]]
Final collection value: [[ 3, Adam ], [ 2, Robert ], [ 1, Julie ]]