java8新特性中stream接口 distinct，sorted，peek，limit，skip reverse() 的用法

实例：

    /**
     * @param invoiceType 发票类型
     * @param reimburseStatus 发票状态
     * @param keyword 关键字
     * @param startTime 开始时间
     * @param endTime 结束时间
     * @param selectLable 标签
     * @param wtUid 委托人账号
     * @return
     */
    private Stream<InvoiceModel> getInvoiceModelStream(String invoiceType, String reimburseStatus, String keyword, String startTime, String endTime, String selectLable, String wtUid) {
        Stream<InvoiceModel> stream = null;
        if (UtilString.isNotEmpty(wtUid)) {
            stream = InvoiceCache.getCache().stream().filter(model -> wtUid.equals(model.getCreateUser())).filter(model -> model.getResultStatus().startsWith(InvoiceConstant.RESULT_STATUS_VALUE_SUCCESS) || model.getResultStatus().startsWith(InvoiceConstant.RESULT_STATUS_VALUE_SUCCESS_WX));//success or success_wx
        } else {
            stream = InvoiceCache.getCache().stream().filter(model -> getContext().getUID().equals(model.getCreateUser())).filter(model -> model.getResultStatus().startsWith(InvoiceConstant.RESULT_STATUS_VALUE_SUCCESS) || model.getResultStatus().startsWith(InvoiceConstant.RESULT_STATUS_VALUE_SUCCESS_WX));
        }
        if (UtilString.isNotEmpty(invoiceType)) {
            stream = stream.filter(model -> invoiceType.equals(model.getTicketType()));
        }
        if (UtilString.isNotEmpty(reimburseStatus)) {
            stream = stream.filter(model -> reimburseStatus.equals(model.getReimburseStatus()));
        }
        if (UtilString.isNotEmpty(selectLable)) {
            stream = stream.filter(invoiceModel -> {
                if (InvoiceConstant.TICKET_TYPE_INVOICE.equals(invoiceModel.getTicketType())) {
                    InvoiceTicketModel model = (InvoiceTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getLableName() != null && model.getLableName().contains(selectLable);
                    }
                } else if (InvoiceConstant.TICKET_TYPE_TRAIN.equals(invoiceModel.getTicketType())) {
                    TrainTicketModel model = (TrainTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getLableName() != null && model.getLableName().contains(selectLable);
                    }
                } else if (InvoiceConstant.TICKET_TYPE_PLANE.equals(invoiceModel.getTicketType())) {
                    AirTicketModel model = (AirTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getLableName() != null && model.getLableName().contains(selectLable);
                    }
                } else if (InvoiceConstant.TICKET_TYPE_MANUAL.equals(invoiceModel.getTicketType())) {
                    OtherTicketModel model = (OtherTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getLableName() != null && model.getLableName().contains(selectLable);
                    }
                }
                return false;
            });
        }

        if (UtilString.isNotEmpty(keyword)) {
            stream = stream.filter(invoiceModel -> {
                if (InvoiceConstant.TICKET_TYPE_INVOICE.equals(invoiceModel.getTicketType())) {
                    InvoiceTicketModel model = (InvoiceTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getSellerTaxName().contains(keyword) || model.getBuyerTaxName().contains(keyword)||model.getAmount().contains(keyword);
                    }
                } else if (InvoiceConstant.TICKET_TYPE_TRAIN.equals(invoiceModel.getTicketType())) {
                    TrainTicketModel model = (TrainTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getName().contains(keyword) || model.getStartLocation().contains(keyword) || model.getEndLocation().contains(keyword) || model.getTrainNumber().contains(keyword)||model.getAmount().contains(keyword);
                    }
                } else if (InvoiceConstant.TICKET_TYPE_PLANE.equals(invoiceModel.getTicketType())) {
                    AirTicketModel model = (AirTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getName().contains(keyword) || model.getStartLocation().contains(keyword) || model.getEndLocation().contains(keyword) || model.getFlightNumber().contains(keyword)||model.getAmount().contains(keyword);
                    }
                } else if (InvoiceConstant.TICKET_TYPE_MANUAL.equals(invoiceModel.getTicketType())) {
                    OtherTicketModel model = (OtherTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getMemo() != null && model.getMemo().contains(keyword)||model.getAmount().contains(keyword);
                    }
                }
                return false;
            });
        }
        if (UtilString.isNotEmpty(startTime)) {
            Timestamp startTimeTS = UtilDate.parseTsFromDateTime(startTime);
            stream = stream.filter(invoiceModel -> {
                if (InvoiceConstant.TICKET_TYPE_INVOICE.equals(invoiceModel.getTicketType())) {
                    InvoiceTicketModel model = (InvoiceTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getBillingDate().compareTo(startTimeTS) >= 0;
                    }
                } else if (InvoiceConstant.TICKET_TYPE_TRAIN.equals(invoiceModel.getTicketType())) {
                    TrainTicketModel model = (TrainTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getStartTime().compareTo(startTimeTS) >= 0 || model.getEndTime().compareTo(startTimeTS) >= 0;
                    }
                } else if (InvoiceConstant.TICKET_TYPE_PLANE.equals(invoiceModel.getTicketType())) {
                    AirTicketModel model = (AirTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getStartTime().compareTo(startTimeTS) >= 0 || model.getEndTime().compareTo(startTimeTS) >= 0;
                    }
                } else if (InvoiceConstant.TICKET_TYPE_MANUAL.equals(invoiceModel.getTicketType())) {
                    OtherTicketModel model = (OtherTicketModel) invoiceModel.getTicketModel();
                    if (model != null && model.getBillingDate() != null) {
                        return model.getBillingDate().compareTo(startTimeTS) >= 0;
                    }
                }
                return false;
            });
        }
        if (UtilString.isNotEmpty(endTime)) {
            Timestamp endTimeTS = UtilDate.parseTsFromDateTime(endTime);
            stream = stream.filter(invoiceModel -> {
                if (InvoiceConstant.TICKET_TYPE_INVOICE.equals(invoiceModel.getTicketType())) {
                    InvoiceTicketModel model = (InvoiceTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getBillingDate().compareTo(endTimeTS) <= 0;
                    }
                } else if (InvoiceConstant.TICKET_TYPE_TRAIN.equals(invoiceModel.getTicketType())) {
                    TrainTicketModel model = (TrainTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getStartTime().compareTo(endTimeTS) <= 0 || model.getEndTime().compareTo(endTimeTS) <= 0;
                    }
                } else if (InvoiceConstant.TICKET_TYPE_PLANE.equals(invoiceModel.getTicketType())) {
                    AirTicketModel model = (AirTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getStartTime().compareTo(endTimeTS) <= 0 || model.getEndTime().compareTo(endTimeTS) <= 0;
                    }
                } else if (InvoiceConstant.TICKET_TYPE_MANUAL.equals(invoiceModel.getTicketType())) {
                    OtherTicketModel model = (OtherTicketModel) invoiceModel.getTicketModel();
                    if (model != null) {
                        return model.getBillingDate().compareTo(endTimeTS) <= 0;
                    }
                }
                return false;
            });
        }
        stream = stream.distinct().sorted(Comparator.comparing(InvoiceModel::getCreateTime).reversed());
        return stream;
    }

    /**
     * 查询发票列表
     *
     * @param skip 跳过的条数
     * @param rowCount 此页查询的条数
     * @param invoiceType 发票类型
     * @param keyword 模糊搜索时的关键词
     * @param startTime 发票时间的范围 - 开始
     * @param endTime 发票时间的范围 - 结束
     * @param selectLable 发票名称
     * @param wtUid 委托人账号
     * @return
     */
    public String querySuccessInvoiceList(int skip, int rowCount, String invoiceType, String reimburseStatus, String keyword, String startTime, String endTime, String selectLable, String wtUid) {
        ResponseObject ro = ResponseObject.newOkResponse();
        try {
            Stream<InvoiceModel> stream1 = getInvoiceModelStream(invoiceType, reimburseStatus, keyword, startTime, endTime, selectLable, wtUid);
            Stream<InvoiceModel> stream3 = getInvoiceModelStream(invoiceType, reimburseStatus, keyword, startTime, endTime, selectLable, wtUid);

            List<InvoiceModel> list = stream1.skip(skip).limit(rowCount).collect(Collectors.toList());
            if (skip == 0) {//第一页需要查询总金额和总张数
                final int[] count = { 0 };
                double sum = stream3.mapToDouble(invoiceModel -> {
                    if (InvoiceConstant.TICKET_TYPE_INVOICE.equals(invoiceModel.getTicketType())) {
                        InvoiceTicketModel model = (InvoiceTicketModel) invoiceModel.getTicketModel();
                        if (model != null) {
                            count[0]++;
                            return Double.parseDouble(model.getAmount());
                        }
                    } else if (InvoiceConstant.TICKET_TYPE_TRAIN.equals(invoiceModel.getTicketType())) {
                        TrainTicketModel model = (TrainTicketModel) invoiceModel.getTicketModel();
                        if (model != null) {
                            count[0]++;
                            return Double.parseDouble(model.getAmount());
                        }
                    } else if (InvoiceConstant.TICKET_TYPE_PLANE.equals(invoiceModel.getTicketType())) {
                        AirTicketModel model = (AirTicketModel) invoiceModel.getTicketModel();
                        if (model != null) {
                            count[0]++;
                            return Double.parseDouble(model.getAmount());
                        }
                    } else if (InvoiceConstant.TICKET_TYPE_MANUAL.equals(invoiceModel.getTicketType())) {
                        OtherTicketModel model = (OtherTicketModel) invoiceModel.getTicketModel();
                        if (model != null) {
                            count[0]++;
                            return Double.parseDouble(model.getAmount());
                        }
                    }
                    return 0;
                }).sum();
                ro.put("sum", String.format("%.2f", sum));
                ro.put("count", count[0]);
            }
            JSONArray ja = getInvoiceJA(list);
            ro.put("list", ja);
            return ro.toString();
        } catch (Exception e) {
            e.printStackTrace();
            return ResponseObject.newErrResponse("查询出错").toString();
        }
    }

//去重复

Stream<T> distinct();

//排序

Stream<T> sorted();

//根据属性排序

Stream<T> sorted(Comparator<? super T> comparator);

//对对象的进行操作

Stream<T> peek(Consumer<? super T> action);

//截断--取先maxSize个对象

Stream<T> limit(long maxSize);

//截断--忽略前N个对象

Stream<T> skip(long n);

下面，我们用一些案例，对这些操作，做一些综合的演示


 
package com.taihao;

 
import java.util.ArrayList;

import java.util.Arrays;

import java.util.Comparator;

import java.util.List;

import java.util.stream.Stream;

 
public class TestJava8 {

public static List<Emp> list = new ArrayList<>();

static {

list.add(new Emp("xiaoHong1", 20, 1000.0));

list.add(new Emp("xiaoHong2", 25, 2000.0));

list.add(new Emp("xiaoHong3", 30, 3000.0));

list.add(new Emp("xiaoHong4", 35, 4000.0));

list.add(new Emp("xiaoHong5", 38, 5000.0));

list.add(new Emp("xiaoHong6", 45, 9000.0));

list.add(new Emp("xiaoHong7", 55, 10000.0));

list.add(new Emp("xiaoHong8", 42, 15000.0));

}

 
public static void println(Stream<Emp> stream) {

stream.forEach(emp -> {

System.out.println(String.format("名字：%s，年纪：%s，薪水：%s", emp.getName(), emp.getAge(), emp.getSalary()));

});

}

 
public static void main(String[] args) {

// 对数组流，先过滤重复，在排序，再控制台输出 1，2，3

Arrays.asList(3, 1, 2, 1).stream().distinct().sorted().forEach(str -> {

System.out.println(str);

});

// 对list里的emp对象，取出薪水，并对薪水进行排序，然后输出薪水的内容，map操作，改变了Strenm的泛型对象

list.stream().map(emp -> emp.getSalary()).sorted().forEach(salary -> {

System.out.println(salary);

});

// 根据emp的属性name，进行排序

println(list.stream().sorted(Comparator.comparing(Emp::getName)));

 
// 给年纪大于30岁的人，薪水提升1.5倍，并输出结果

Stream<Emp> stream = list.stream().filter(emp -> {

return emp.getAge() > 30;

}).peek(emp -> {

emp.setSalary(emp.getSalary() * 1.5);

});

println(stream);

// 数字从1开始迭代（无限流），下一个数字，是上个数字+1，忽略前5个 ，并且只取10个数字

// 原本1-无限，忽略前5个，就是1-5数字，不要，从6开始，截取10个，就是6-15

Stream.iterate(1, x -> ++x).skip(5).limit(10).forEach(System.out::println);

}

 
public static class Emp {

private String name;

 
private Integer age;

 
private Double salary;

 
public Emp(String name, Integer age, Double salary) {

super();

this.name = name;

this.age = age;

this.salary = salary;

}

 
public String getName() {

return name;

}

 
public void setName(String name) {

this.name = name;

}

 
public Integer getAge() {

return age;

}

 
public void setAge(Integer age) {

this.age = age;

}

 
public Double getSalary() {

return salary;

}

 
public void setSalary(Double salary) {

this.salary = salary;

}

 
}

}

reverse()

是python中列表的一个内置方法（也就是说，在字典，字符串或者元组中，是没有这个内置方法的），用于列表中数据的反转；

exp：

lista = [1, 2, 3, 4]

lista.reverse()

print(lista)

打印结果：

[4, 3, 2, 1]

1. //去重复

2. Stream<T> distinct();

3. //排序

4. Stream<T> sorted();

5. //根据属性排序

6. Stream<T> sorted(Comparator<? super T> comparator);

7. //对对象的进行操作

8. Stream<T> peek(Consumer<? super T> action);

9. //截断--取先maxSize个对象

10. Stream<T> limit(long maxSize);

11. //截断--忽略前N个对象

12. Stream<T> skip(long n);

下面，我们用一些案例，对这些操作，做一些综合的演示

1. package com.taihao;

2.  

3. import java.util.ArrayList;

4. import java.util.Arrays;

5. import java.util.Comparator;

6. import java.util.List;

7. import java.util.stream.Stream;

8.  

9. public class TestJava8 {

10. public static List<Emp> list = new ArrayList<>();

11. static {

12. list.add(new Emp("xiaoHong1", 20, 1000.0));

13. list.add(new Emp("xiaoHong2", 25, 2000.0));

14. list.add(new Emp("xiaoHong3", 30, 3000.0));

15. list.add(new Emp("xiaoHong4", 35, 4000.0));

16. list.add(new Emp("xiaoHong5", 38, 5000.0));

17. list.add(new Emp("xiaoHong6", 45, 9000.0));

18. list.add(new Emp("xiaoHong7", 55, 10000.0));

19. list.add(new Emp("xiaoHong8", 42, 15000.0));

20. }

21.  

22. public static void println(Stream<Emp> stream) {

23. stream.forEach(emp -> {

24. System.out.println(String.format("名字：%s，年纪：%s，薪水：%s", emp.getName(), emp.getAge(), emp.getSalary()));

25. });

26. }

27.  

28. public static void main(String[] args) {

29. // 对数组流，先过滤重复，在排序，再控制台输出 1，2，3

30. Arrays.asList(3, 1, 2, 1).stream().distinct().sorted().forEach(str -> {

31. System.out.println(str);

32. });

33. // 对list里的emp对象，取出薪水，并对薪水进行排序，然后输出薪水的内容，map操作，改变了Strenm的泛型对象

34. list.stream().map(emp -> emp.getSalary()).sorted().forEach(salary -> {

35. System.out.println(salary);

36. });

37. // 根据emp的属性name，进行排序

38. println(list.stream().sorted(Comparator.comparing(Emp::getName)));

39.  

40. // 给年纪大于30岁的人，薪水提升1.5倍，并输出结果

41. Stream<Emp> stream = list.stream().filter(emp -> {

42. return emp.getAge() > 30;

43. }).peek(emp -> {

44. emp.setSalary(emp.getSalary() * 1.5);

45. });

46. println(stream);

47. // 数字从1开始迭代（无限流），下一个数字，是上个数字+1，忽略前5个 ，并且只取10个数字

48. // 原本1-无限，忽略前5个，就是1-5数字，不要，从6开始，截取10个，就是6-15

49. Stream.iterate(1, x -> ++x).skip(5).limit(10).forEach(System.out::println);

50. }

51.  

52. public static class Emp {

53. private String name;

54.  

55. private Integer age;

56.  

57. private Double salary;

58.  

59. public Emp(String name, Integer age, Double salary) {

60. super();

61. this.name = name;

62. this.age = age;

63. this.salary = salary;

64. }

65.  

66. public String getName() {

67. return name;

68. }

69.  

70. public void setName(String name) {

71. this.name = name;

72. }

73.  

74. public Integer getAge() {

75. return age;

76. }

77.  

78. public void setAge(Integer age) {

79. this.age = age;

80. }

81.  

82. public Double getSalary() {

83. return salary;

84. }

85.  

86. public void setSalary(Double salary) {

87. this.salary = salary;

88. }

89.  

90. }

91. }