comparable-and-comparator-in-java-example

package com.sort;

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


//Use of  comparable
public class SortArrayList {

public static void main(String [] args) {

List<Topics> lt = new ArrayList<Topics>();

lt.add(new Topics("1","a", "Test1"));

lt.add(new Topics("6","b", "Test6"));
lt.add(new Topics("5","c", "Test5"));

lt.add(new Topics("1","d", "Test2"));

Collections.sort(lt);

for (Topics topic : lt) {
System.out.println(topic.getName());
}


}
}

Topics.java

package com.sort;

public class Topics implements Comparable<Topics>

{

private String id;

private String name;

private String description;

public String getId() {

return id;

}

public void setId(String id) {

this.id = id;

}

public Topics() {

}

public Topics(String id, String name, String description) {

super();

this.id = id;

this.name = name;

this.description = description;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getDescription() {

return description;

}

public void setDescription(String description) {

this.description = description;

}

//this method we need to implement to provide the sorting based on ID 

      @Override public int compareTo(Topics o) {

  return Integer.parseInt(this.id)- Integer.parseInt(o.id); }

}

Output 

a

d

c

b

Topics