Sort a Java collection object based on one field in it

Question

I have the following collection:

Collection<AgentSummaryDTO> agentDtoList = new ArrayList<AgentSummaryDTO>();

Where AgentSummaryDTO looks like this:

public class AgentSummaryDTO implements Serializable {
    private Long id;
    private String agentName;
    private String agentCode;
    private String status;
    private Date createdDate;
    private Integer customerCount;
}

Now I have to sort the collection agentDtoList based on the customerCount field, how to achieve this?

Answer 1

here is my "1liner":

Collections.sort(agentDtoList, new Comparator<AgentSummaryDTO>(){
   public int compare(AgentSummaryDTO o1, AgentSummaryDTO o2){
      return o1.getCustomerCount() - o2.getCustomerCount();
   }
});

UPDATE for Java 8: For int datatype

 Collections.sort(agentDtoList, (o1, o2) -> o1.getCustomerCount() - o2.getCustomerCount());

or even:

 Collections.sort(agentDtoList, Comparator.comparing(AgentSummaryDTO::getCustomerCount));

For String datatype (as in comment)

Collections.sort(list, (o1, o2) -> (o1.getAgentName().compareTo(o2.getAgentName())));

..it expects getter AgentSummaryDTO.getCustomerCount()