Sort a Java collection object based on one field in it

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()

The answer by Jiri Kremser can be simplified even further, which really is the full Java 8 way to do it:

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

This simply compares by the integer field, and works well since Integer implements Comparable.

An even cleaner solution might be to use the built-in comparingInt() method:

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

Of course, this could be expressed even shorter by statically importing sort and comparingInt:

sort(agentDtoList, comparingInt(AgentSummaryDTO::getCustomerCount));