[Java 8] Using lambda to convert a List of object to comma-separated string

If I java an object which named Group

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import lombok.Data; @Data public class Group { private Integer id; private String name; }

The data in List of Group looks like:

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Group(id=1, name=Group A) Group(id=2, name=Group B) Group(id=3, name=Group C)

The expected result is to convert to comma-separated string: 
Group A, Group B, Group c

If we does not utilize lambda expression, the code snippet is as following:

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List<Group> groups = dto.getUser().getGroups(); StringBuilder groupStringBuilder = new StringBuilder(); for (int i = 0; i < groups.size(); i++) { if (i == groups.size() - 1) { groupStringBuilder = groupStringBuilder.append(groups.get(i).getName()); } else { groupStringBuilder = groupStringBuilder.append(groups.get(i).getName()).append(", "); } }

If we apply lambda expression, we only need to use one line of code to meet this requirement:

    String groupStr = groups.stream().map(g -> g.getName()).collect(Collectors.joining(", "));