Java Collections.rotate() Example
September 05, 2021
rotate() of Java java.util.Collections class. The Collections.rotate() method rotates the elements of a Java list for the given distance. We can also rotate the sublist for the given distance within a list. Find its method syntax.
public static void rotate(List<?> list, int distance)
1. {A B C} after rotating for distance= -1
{B C A}
2. {A B C} after rotating for distance= 1
{C A B}
MyApp.java
package com.concretepage;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class MyApp {
public static void main(String[] args) {
User u1 = new User("A");
User u2 = new User("B");
User u3 = new User("C");
List<User> list = Arrays.asList(u1, u2, u3);
System.out.println("before rotate");
list.forEach(u -> System.out.print(u.getName()+ " ")); //A B C
System.out.println("\nafter rotating by distnace 2");
Collections.rotate(list, 2);
list.forEach(u -> System.out.print(u.getName()+ " ")); //B C A
System.out.println("\nafter rotating by distnace -1");
Collections.rotate(list, -1);
list.forEach(u -> System.out.print(u.getName()+ " ")); //C A B
}
}
class User {
private String name;
public User(String name) {
this.name = name;
}
public String getName() {
return name;
}
}
before rotate A B C after rotating by distnace 2 B C A after rotating by distnace -1 C A B
Collections.rotate with SubList
Now we will rotate a sub list within a list. Find the example.RotateSubList.java
package com.concretepage;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
public class RotateSubList {
public static void main(String[] args) {
List<Integer> list = Arrays.asList(1, 2, 3, 4, 5, 6, 7, 8);
System.out.println("List before rotate");
list.forEach(n -> System.out.print(n + " "));
System.out.println("\nlist.subList(2, 5)");
list.subList(2, 5).forEach(n -> System.out.print(n + " "));
System.out.println("\nList after rotating sublist by distnace 1");
Collections.rotate(list.subList(2, 5), 1);
list.forEach(n -> System.out.print(n + " "));
}
}
List before rotate 1 2 3 4 5 6 7 8 list.subList(2, 5) 3 4 5 List after rotating sublist by distnace 1 1 2 5 3 4 6 7 8
