Java8的语法使用

List list = new ArrayList<>();
list.add(new Entity("刘备",28));
list.add(new Entity("关羽",27));
list.add(new Entity("张飞",26));

String userNames = list.stream().map(Entity::getUsername).collect(Collectors.joining(","));
String ages = list.stream().map(entity -> entity.getAge()+"").collect(Collectors.joining(","));
System.out.println("userNames: "+userNames);
System.out.println("ages: "+ages);

结果：