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  • Stream Collector

         // Accumulate names into a List
         List<String> list = people.stream().map(Person::getName).collect(Collectors.toList());
    
         // Accumulate names into a TreeSet
         Set<String> set = people.stream().map(Person::getName).collect(Collectors.toCollection(TreeSet::new));
    
         // Convert elements to strings and concatenate them, separated by commas
         String joined = things.stream()
                               .map(Object::toString)
                               .collect(Collectors.joining(", "));
    
         // Compute sum of salaries of employee
         int total = employees.stream()
                              .collect(Collectors.summingInt(Employee::getSalary)));
    
         // Group employees by department
         Map<Department, List<Employee>> byDept
             = employees.stream()
                        .collect(Collectors.groupingBy(Employee::getDepartment));
    
         // Compute sum of salaries by department
         Map<Department, Integer> totalByDept
             = employees.stream()
                        .collect(Collectors.groupingBy(Employee::getDepartment,
                                                       Collectors.summingInt(Employee::getSalary)));
    
         // Partition students into passing and failing
         Map<Boolean, List<Student>> passingFailing =
             students.stream()
                     .collect(Collectors.partitioningBy(s -> s.getGrade() >= PASS_THRESHOLD));
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  • 原文地址:https://www.cnblogs.com/feika/p/4576808.html
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