• 泛型的使用案例，以及年月日的定制排序，传入Comparator对象

     

    简易版：传送门：过关展将之——birthday排序（年月日排序）-CSDN博客  

     实现过程;

    1. public static void main(String[] args) {
    2.         ArrayList arrayList = new ArrayList<>();
    3.         Employee grace = new Employee("Grace", 12000, new MyDate(2012, 12, 12));
    4.         Employee tom = new Employee("Tom", 28000, new MyDate(2001, 12, 03));
    5.         Employee david = new Employee("David", 30000, new MyDate(1999, 10, 10));
    6.         Employee david1 = new Employee("David", 31000, new MyDate(2001, 11, 15));
    7.         Employee david2 = new Employee("David", 32000, new MyDate(1899, 5, 14));
    8.         Employee david3 = new Employee("David", 33000, new MyDate(2013, 04, 11));
    9.         Employee david4 = new Employee("David", 34000, new MyDate(1987, 04, 10));
    10.         Employee david5 = new Employee("David", 34000, new MyDate(1987, 04, 11));
    11.         arrayList.add(grace);
    12.         arrayList.add(tom);
    13.         arrayList.add(david);
    14.         arrayList.add(david1);
    15.         arrayList.add(david2);
    16.         arrayList.add(david3);
    17.         arrayList.add(david4);
    18.         arrayList.add(david5);
    19. //        System.out.println("打印先前数据：" + arrayList);
    20.         //现在进行排序
    21.         arrayList.sort(new Comparator() {
    22.             @Override
    23.             public int compare(Employee o1, Employee o2) {
    24.                 if (!(o1.getName() != null && o2.getName() != null)) {
    25.                     throw new RuntimeException("员工姓名不能为空！");
    26.                 }else{
    27.                     if (o1.getName().equals(o2.getName())) {
    28.                         if (o1.getBirthday().getYear() == o2.getBirthday().getYear()) {
    29.                             if (o1.getBirthday().getMonth() == o2.getBirthday().getMonth()) {
    30.                                 if (o1.getBirthday().getDay() == o2.getBirthday().getDay()) {
    31.                                     return 0;
    32.                                 } else if (o1.getBirthday().getDay() > o2.getBirthday().getDay()) {
    33.                                     return 1;
    34.                                 } else {
    35.                                     return -1;
    36.                                 }
    37.                             } else if (o1.getBirthday().getMonth() > o2.getBirthday().getMonth()) {
    38.                                 return 1;
    39.                             } else {
    40.                                 return -1;
    41.                             }
    42.                         } else if (o1.getBirthday().getYear() > o2.getBirthday().getYear()) {
    43.                             return 1;
    44.                         } else {
    45.                             return -1;
    46.                         }
    47.                     } else {
    48.                         return o1.getName().compareTo(o2.getName());
    49.                     }
    50.                 }
    51.             }
    52.         });
    53.         System.out.println("========排序后======");
    54.         for (Object o :arrayList) {
    55.             Employee employee = (Employee) o;
    56.             System.out.println(employee);
    57.         }
    58.  
    59.     }
    60. }
    61.  
    62. class MyDate {
    63.     private int year;
    64.     private int month;
    65.     private int day;
    66.  
    67.     public MyDate(int year, int month, int day) {
    68.         this.year = year;
    69.         this.month = month;
    70.         this.day = day;
    71.     }
    72.  
    73.     public int getYear() {
    74.         return year;
    75.     }
    76.  
    77.     public void setYear(int year) {
    78.         this.year = year;
    79.     }
    80.  
    81.     public int getMonth() {
    82.         return month;
    83.     }
    84.  
    85.     public void setMonth(int month) {
    86.         this.month = month;
    87.     }
    88.  
    89.     public int getDay() {
    90.         return day;
    91.     }
    92.  
    93.     public void setDay(int day) {
    94.         this.day = day;
    95.     }
    96.  
    97.     @Override
    98.     public String toString() {
    99.         return "MyDate{" +
    100.                 "year=" + year +
    101.                 ", month=" + month +
    102.                 ", day=" + day +
    103.                 '}';
    104.     }
    105. }
    106.  
    107. class Employee {
    108.  
    109.     private String name;
    110.  
    111.     @Override
    112.     public String toString() {
    113.         return "Employee{" +
    114.                 "name='" + name + '\'' +
    115.                 ", sal=" + sal +
    116.                 ", birthday=" + birthday +
    117.                 '}';
    118.     }
    119.  
    120.     private double sal;
    121.  
    122.     public String getName() {
    123.         return name;
    124.     }
    125.  
    126.     public void setName(String name) {
    127.         this.name = name;
    128.     }
    129.  
    130.     public double getSal() {
    131.         return sal;
    132.     }
    133.  
    134.     public void setSal(double sal) {
    135.         this.sal = sal;
    136.     }
    137.  
    138.     public MyDate getBirthday() {
    139.         return birthday;
    140.     }
    141.  
    142.     public void setBirthday(MyDate birthday) {
    143.         this.birthday = birthday;
    144.     }
    145.  
    146.     private MyDate birthday;
    147.  
    148.     public Employee(String name, double sal, MyDate birthday) {
    149.         this.name = name;
    150.         this.sal = sal;
    151.         this.birthday = birthday;
    152.     }
    153. }

     以上代码过于繁琐，使用 if 的嵌套，可读性不高，现在进行改良：

    进一步优化过程：

    1.  @SuppressWarnings({"all"})
    2.     public static void main(String[] args) {
    3.         ArrayList arrayList = new ArrayList<>();
    4.         EmployeeImp grace = new EmployeeImp("Grace", 12000, new MyDateImp(2012, 12, 12));
    5.         EmployeeImp tom = new EmployeeImp("Tom", 28000, new MyDateImp(2001, 12, 03));
    6.         EmployeeImp david = new EmployeeImp("David", 30000, new MyDateImp(1999, 10, 10));
    7.         EmployeeImp david1 = new EmployeeImp("David", 31000, new MyDateImp(2001, 11, 15));
    8.         EmployeeImp david2 = new EmployeeImp("David", 32000, new MyDateImp(1899, 5, 14));
    9.         EmployeeImp david3 = new EmployeeImp("David", 33000, new MyDateImp(2013, 04, 11));
    10.         EmployeeImp david4 = new EmployeeImp("David", 34000, new MyDateImp(1987, 04, 10));
    11.         EmployeeImp david5 = new EmployeeImp("David", 34000, new MyDateImp(1987, 04, 11));
    12.         arrayList.add(grace);
    13.         arrayList.add(tom);
    14.         arrayList.add(david);
    15.         arrayList.add(david1);
    16.         arrayList.add(david2);
    17.         arrayList.add(david3);
    18.         arrayList.add(david4);
    19.         arrayList.add(david5);
    20.  
    21.         //下面开始订制排序
    22.         arrayList.sort(new Comparator() {
    23.             @Override
    24.             public int compare(EmployeeImp o1, EmployeeImp o2) {
    25.                 if (!(o1 instanceof EmployeeImp && o2 instanceof EmployeeImp)) {
    26.                     System.out.println("类型不匹配");
    27.                     return 0;
    28.                 }
    29.                 //比较name
    30.                 int i = o1.getName().compareTo(o2.getName());
    31.                 if (i==0) {//如果名字相同，就继续比较
    32.                     int yearMinus =o1.getBirthday().getYear() - o2.getBirthday().getYear();
    33.                     if(yearMinus==0){//如果两个年份相同，继续比较月份
    34.                         int monthMinus = o1.getBirthday().getMonth()- o2.getBirthday().getMonth();
    35.                         if(monthMinus==0){//如果两个月份相同，继续比较日
    36.                             int dayMinus = o1.getBirthday().getDay()- o2.getBirthday().getDay();
    37.                             if(dayMinus==0){
    38.                                 return 0;
    39.                             }else{
    40.                                 return dayMinus;
    41.                             }
    42.                         }else{
    43.                             return monthMinus;
    44.                         }
    45.                     }else{
    46.                         return yearMinus;
    47.                     }
    48.  
    49.                 } else{//如果名字不相同，就返回，出结果
    50.                     return i;
    51.                 }
    52.             }
    53.         });
    54.         System.out.println("======定制排序后=====");
    55.         for (Object o :arrayList) {
    56.             EmployeeImp employeeImp = (EmployeeImp) o;
    57.             System.out.println(employeeImp);
    58.         }
    59.     }
    60. }
    61.  
    62. class MyDateImp {
    63.     private int year;
    64.     private int month;
    65.     private int day;
    66.  
    67.     public MyDateImp(int year, int month, int day) {
    68.         this.year = year;
    69.         this.month = month;
    70.         this.day = day;
    71.     }
    72.  
    73.     public int getYear() {
    74.         return year;
    75.     }
    76.  
    77.     public void setYear(int year) {
    78.         this.year = year;
    79.     }
    80.  
    81.     public int getMonth() {
    82.         return month;
    83.     }
    84.  
    85.     public void setMonth(int month) {
    86.         this.month = month;
    87.     }
    88.  
    89.     public int getDay() {
    90.         return day;
    91.     }
    92.  
    93.     public void setDay(int day) {
    94.         this.day = day;
    95.     }
    96.  
    97.     @Override
    98.     public String toString() {
    99.         return "MyDate{" +
    100.                 "year=" + year +
    101.                 ", month=" + month +
    102.                 ", day=" + day +
    103.                 '}';
    104.     }
    105. }
    106.  
    107. class EmployeeImp {
    108.  
    109.     private String name;
    110.  
    111.     @Override
    112.     public String toString() {
    113.         return "Employee{" +
    114.                 "name='" + name + '\'' +
    115.                 ", sal=" + sal +
    116.                 ", birthday=" + birthday +
    117.                 '}';
    118.     }
    119.  
    120.     private double sal;
    121.  
    122.     public String getName() {
    123.         return name;
    124.     }
    125.  
    126.     public void setName(String name) {
    127.         this.name = name;
    128.     }
    129.  
    130.     public double getSal() {
    131.         return sal;
    132.     }
    133.  
    134.     public void setSal(double sal) {
    135.         this.sal = sal;
    136.     }
    137.  
    138.     public MyDateImp getBirthday() {
    139.         return birthday;
    140.     }
    141.  
    142.     public void setBirthday(MyDateImp birthday) {
    143.         this.birthday = birthday;
    144.     }
    145.  
    146.     private MyDateImp birthday;
    147.  
    148.     public EmployeeImp(String name, double sal, MyDateImp birthday) {
    149.         this.name = name;
    150.         this.sal = sal;
    151.         this.birthday = birthday;
    152.     }
    153. }

    使用过关斩将法改良：

    1.    public static void main(String[] args) {
    2.         ArrayList arrayList = new ArrayList<>();
    3.         EmployeeImp grace = new EmployeeImp("Grace", 12000, new MyDateImp(2012, 12, 12));
    4.         EmployeeImp tom = new EmployeeImp("Tom", 28000, new MyDateImp(2001, 12, 03));
    5.         EmployeeImp david = new EmployeeImp("David", 30000, new MyDateImp(1999, 10, 10));
    6.         EmployeeImp david1 = new EmployeeImp("David", 31000, new MyDateImp(2001, 11, 15));
    7.         EmployeeImp david2 = new EmployeeImp("David", 32000, new MyDateImp(1899, 5, 14));
    8.         EmployeeImp david3 = new EmployeeImp("David", 33000, new MyDateImp(2013, 04, 11));
    9.         EmployeeImp david4 = new EmployeeImp("David", 34000, new MyDateImp(1987, 04, 10));
    10.         EmployeeImp david5 = new EmployeeImp("David", 34000, new MyDateImp(1987, 04, 11));
    11.         arrayList.add(grace);
    12.         arrayList.add(tom);
    13.         arrayList.add(david);
    14.         arrayList.add(david1);
    15.         arrayList.add(david2);
    16.         arrayList.add(david3);
    17.         arrayList.add(david4);
    18.         arrayList.add(david5);
    19.  
    20.         //下面开始订制排序
    21.         arrayList.sort(new Comparator() {
    22.             @Override
    23.             public int compare(EmployeeImp o1, EmployeeImp o2) {
    24.                 if (!(o1 instanceof EmployeeImp && o2 instanceof EmployeeImp)) {
    25.                     System.out.println("类型不匹配");
    26.                     return 0;
    27.                 }
    28.                 //比较name
    29.                 int i = o1.getName().compareTo(o2.getName());
    30.                 if (i != 0) {//如果名字不相同，直接返回
    31.                     return i;
    32.                 }
    33.                 //以下是对birthday的比较，因此，我们最好把这个比较，放在MyDate
    34.                 int yearMinus = o1.getBirthday().getYear() - o2.getBirthday().getYear();
    35.                 if (yearMinus != 0) {//如果两个年份不相同，直接返回
    36.                     return yearMinus;
    37.                 }
    38.                 int monthMinus = o1.getBirthday().getMonth() - o2.getBirthday().getMonth();
    39.                 if (monthMinus != 0) {//如果两个月份不相同，直接返回
    40.                     return monthMinus;
    41.                 }
    42.                 //如果year、month都相同
    43.                     return o1.getBirthday().getDay() - o2.getBirthday().getDay();
    44.             }
    45.         });
    46.         System.out.println("======定制排序后=====");
    47.         for (
    48.                 Object o : arrayList) {
    49.             EmployeeImp employeeImp = (EmployeeImp) o;
    50.             System.out.println(employeeImp);
    51.         }
    52.     }
    53. }
    54.  
    55. class MyDateImp {
    56.     private int year;
    57.     private int month;
    58.     private int day;
    59.  
    60.     public MyDateImp(int year, int month, int day) {
    61.         this.year = year;
    62.         this.month = month;
    63.         this.day = day;
    64.     }
    65.  
    66.     public int getYear() {
    67.         return year;
    68.     }
    69.  
    70.     public void setYear(int year) {
    71.         this.year = year;
    72.     }
    73.  
    74.     public int getMonth() {
    75.         return month;
    76.     }
    77.  
    78.     public void setMonth(int month) {
    79.         this.month = month;
    80.     }
    81.  
    82.     public int getDay() {
    83.         return day;
    84.     }
    85.  
    86.     public void setDay(int day) {
    87.         this.day = day;
    88.     }
    89.  
    90.     @Override
    91.     public String toString() {
    92.         return "MyDate{" +
    93.                 "year=" + year +
    94.                 ", month=" + month +
    95.                 ", day=" + day +
    96.                 '}';
    97.     }
    98. }
    99.  
    100. class EmployeeImp {
    101.  
    102.     private String name;
    103.  
    104.     @Override
    105.     public String toString() {
    106.         return "Employee{" +
    107.                 "name='" + name + '\'' +
    108.                 ", sal=" + sal +
    109.                 ", birthday=" + birthday +
    110.                 '}';
    111.     }
    112.  
    113.     private double sal;
    114.  
    115.     public String getName() {
    116.         return name;
    117.     }
    118.  
    119.     public void setName(String name) {
    120.         this.name = name;
    121.     }
    122.  
    123.     public double getSal() {
    124.         return sal;
    125.     }
    126.  
    127.     public void setSal(double sal) {
    128.         this.sal = sal;
    129.     }
    130.  
    131.     public MyDateImp getBirthday() {
    132.         return birthday;
    133.     }
    134.  
    135.     public void setBirthday(MyDateImp birthday) {
    136.         this.birthday = birthday;
    137.     }
    138.  
    139.     private MyDateImp birthday;
    140.  
    141.     public EmployeeImp(String name, double sal, MyDateImp birthday) {
    142.         this.name = name;
    143.         this.sal = sal;
    144.         this.birthday = birthday;
    145.     }
    146. }

     

    打印结果：

    简易版：传送门：过关展将之——birthday排序（年月日排序）-CSDN博客 

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  • 原文地址：https://blog.csdn.net/qq_58341172/article/details/133982935