泛型的使用案例，以及年月日的定制排序，传入Comparator对象

年月日的定制排序，传入Comparator对象"/>

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;

public static void main(String[] args) {ArrayList<Employee> arrayList = new ArrayList<>();Employee grace = new Employee("Grace", 12000, new MyDate(2012, 12, 12));Employee tom = new Employee("Tom", 28000, new MyDate(2001, 12, 03));Employee david = new Employee("David", 30000, new MyDate(1999, 10, 10));Employee david1 = new Employee("David", 31000, new MyDate(2001, 11, 15));Employee david2 = new Employee("David", 32000, new MyDate(1899, 5, 14));Employee david3 = new Employee("David", 33000, new MyDate(2013, 04, 11));Employee david4 = new Employee("David", 34000, new MyDate(1987, 04, 10));Employee david5 = new Employee("David", 34000, new MyDate(1987, 04, 11));arrayList.add(grace);arrayList.add(tom);arrayList.add(david);arrayList.add(david1);arrayList.add(david2);arrayList.add(david3);arrayList.add(david4);arrayList.add(david5);
//        System.out.println("打印先前数据：" + arrayList);//现在进行排序arrayList.sort(new Comparator<Employee>() {@Overridepublic int compare(Employee o1, Employee o2) {if (!(o1.getName() != null && o2.getName() != null)) {throw new RuntimeException("员工姓名不能为空！");}else{if (o1.getName().equals(o2.getName())) {if (o1.getBirthday().getYear() == o2.getBirthday().getYear()) {if (o1.getBirthday().getMonth() == o2.getBirthday().getMonth()) {if (o1.getBirthday().getDay() == o2.getBirthday().getDay()) {return 0;} else if (o1.getBirthday().getDay() > o2.getBirthday().getDay()) {return 1;} else {return -1;}} else if (o1.getBirthday().getMonth() > o2.getBirthday().getMonth()) {return 1;} else {return -1;}} else if (o1.getBirthday().getYear() > o2.getBirthday().getYear()) {return 1;} else {return -1;}} else {return o1.getName()pareTo(o2.getName());}}}});System.out.println("========排序后======");for (Object o :arrayList) {Employee employee = (Employee) o;System.out.println(employee);}}
}class MyDate {private int year;private int month;private int day;public MyDate(int year, int month, int day) {this.year = year;this.month = month;this.day = day;}public int getYear() {return year;}public void setYear(int year) {this.year = year;}public int getMonth() {return month;}public void setMonth(int month) {this.month = month;}public int getDay() {return day;}public void setDay(int day) {this.day = day;}@Overridepublic String toString() {return "MyDate{" +"year=" + year +", month=" + month +", day=" + day +'}';}
}class Employee {private String name;@Overridepublic String toString() {return "Employee{" +"name='" + name + '\'' +", sal=" + sal +", birthday=" + birthday +'}';}private double sal;public String getName() {return name;}public void setName(String name) {this.name = name;}public double getSal() {return sal;}public void setSal(double sal) {this.sal = sal;}public MyDate getBirthday() {return birthday;}public void setBirthday(MyDate birthday) {this.birthday = birthday;}private MyDate birthday;public Employee(String name, double sal, MyDate birthday) {this.name = name;this.sal = sal;this.birthday = birthday;}
}

 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：

 @SuppressWarnings({"all"})public static void main(String[] args) {ArrayList<EmployeeImp> arrayList = new ArrayList<>();EmployeeImp grace = new EmployeeImp("Grace", 12000, new MyDateImp(2012, 12, 12));EmployeeImp tom = new EmployeeImp("Tom", 28000, new MyDateImp(2001, 12, 03));EmployeeImp david = new EmployeeImp("David", 30000, new MyDateImp(1999, 10, 10));EmployeeImp david1 = new EmployeeImp("David", 31000, new MyDateImp(2001, 11, 15));EmployeeImp david2 = new EmployeeImp("David", 32000, new MyDateImp(1899, 5, 14));EmployeeImp david3 = new EmployeeImp("David", 33000, new MyDateImp(2013, 04, 11));EmployeeImp david4 = new EmployeeImp("David", 34000, new MyDateImp(1987, 04, 10));EmployeeImp david5 = new EmployeeImp("David", 34000, new MyDateImp(1987, 04, 11));arrayList.add(grace);arrayList.add(tom);arrayList.add(david);arrayList.add(david1);arrayList.add(david2);arrayList.add(david3);arrayList.add(david4);arrayList.add(david5);//下面开始订制排序arrayList.sort(new Comparator<EmployeeImp>() {@Overridepublic int compare(EmployeeImp o1, EmployeeImp o2) {if (!(o1 instanceof EmployeeImp && o2 instanceof EmployeeImp)) {System.out.println("类型不匹配");return 0;}//比较nameint i = o1.getName()pareTo(o2.getName());if (i==0) {//如果名字相同，就继续比较int yearMinus =o1.getBirthday().getYear() - o2.getBirthday().getYear();if(yearMinus==0){//如果两个年份相同，继续比较月份int monthMinus = o1.getBirthday().getMonth()- o2.getBirthday().getMonth();if(monthMinus==0){//如果两个月份相同，继续比较日int dayMinus = o1.getBirthday().getDay()- o2.getBirthday().getDay();if(dayMinus==0){return 0;}else{return dayMinus;}}else{return monthMinus;}}else{return yearMinus;}} else{//如果名字不相同，就返回，出结果return i;}}});System.out.println("======定制排序后=====");for (Object o :arrayList) {EmployeeImp employeeImp = (EmployeeImp) o;System.out.println(employeeImp);}}
}class MyDateImp {private int year;private int month;private int day;public MyDateImp(int year, int month, int day) {this.year = year;this.month = month;this.day = day;}public int getYear() {return year;}public void setYear(int year) {this.year = year;}public int getMonth() {return month;}public void setMonth(int month) {this.month = month;}public int getDay() {return day;}public void setDay(int day) {this.day = day;}@Overridepublic String toString() {return "MyDate{" +"year=" + year +", month=" + month +", day=" + day +'}';}
}class EmployeeImp {private String name;@Overridepublic String toString() {return "Employee{" +"name='" + name + '\'' +", sal=" + sal +", birthday=" + birthday +'}';}private double sal;public String getName() {return name;}public void setName(String name) {this.name = name;}public double getSal() {return sal;}public void setSal(double sal) {this.sal = sal;}public MyDateImp getBirthday() {return birthday;}public void setBirthday(MyDateImp birthday) {this.birthday = birthday;}private MyDateImp birthday;public EmployeeImp(String name, double sal, MyDateImp birthday) {this.name = name;this.sal = sal;this.birthday = birthday;}
}

使用过关斩将法改良：

   public static void main(String[] args) {ArrayList<EmployeeImp> arrayList = new ArrayList<>();EmployeeImp grace = new EmployeeImp("Grace", 12000, new MyDateImp(2012, 12, 12));EmployeeImp tom = new EmployeeImp("Tom", 28000, new MyDateImp(2001, 12, 03));EmployeeImp david = new EmployeeImp("David", 30000, new MyDateImp(1999, 10, 10));EmployeeImp david1 = new EmployeeImp("David", 31000, new MyDateImp(2001, 11, 15));EmployeeImp david2 = new EmployeeImp("David", 32000, new MyDateImp(1899, 5, 14));EmployeeImp david3 = new EmployeeImp("David", 33000, new MyDateImp(2013, 04, 11));EmployeeImp david4 = new EmployeeImp("David", 34000, new MyDateImp(1987, 04, 10));EmployeeImp david5 = new EmployeeImp("David", 34000, new MyDateImp(1987, 04, 11));arrayList.add(grace);arrayList.add(tom);arrayList.add(david);arrayList.add(david1);arrayList.add(david2);arrayList.add(david3);arrayList.add(david4);arrayList.add(david5);//下面开始订制排序arrayList.sort(new Comparator<EmployeeImp>() {@Overridepublic int compare(EmployeeImp o1, EmployeeImp o2) {if (!(o1 instanceof EmployeeImp && o2 instanceof EmployeeImp)) {System.out.println("类型不匹配");return 0;}//比较nameint i = o1.getName()pareTo(o2.getName());if (i != 0) {//如果名字不相同，直接返回return i;}//以下是对birthday的比较，因此，我们最好把这个比较，放在MyDateint yearMinus = o1.getBirthday().getYear() - o2.getBirthday().getYear();if (yearMinus != 0) {//如果两个年份不相同，直接返回return yearMinus;}int monthMinus = o1.getBirthday().getMonth() - o2.getBirthday().getMonth();if (monthMinus != 0) {//如果两个月份不相同，直接返回return monthMinus;}//如果year、month都相同return o1.getBirthday().getDay() - o2.getBirthday().getDay();}});System.out.println("======定制排序后=====");for (Object o : arrayList) {EmployeeImp employeeImp = (EmployeeImp) o;System.out.println(employeeImp);}}
}class MyDateImp {private int year;private int month;private int day;public MyDateImp(int year, int month, int day) {this.year = year;this.month = month;this.day = day;}public int getYear() {return year;}public void setYear(int year) {this.year = year;}public int getMonth() {return month;}public void setMonth(int month) {this.month = month;}public int getDay() {return day;}public void setDay(int day) {this.day = day;}@Overridepublic String toString() {return "MyDate{" +"year=" + year +", month=" + month +", day=" + day +'}';}
}class EmployeeImp {private String name;@Overridepublic String toString() {return "Employee{" +"name='" + name + '\'' +", sal=" + sal +", birthday=" + birthday +'}';}private double sal;public String getName() {return name;}public void setName(String name) {this.name = name;}public double getSal() {return sal;}public void setSal(double sal) {this.sal = sal;}public MyDateImp getBirthday() {return birthday;}public void setBirthday(MyDateImp birthday) {this.birthday = birthday;}private MyDateImp birthday;public EmployeeImp(String name, double sal, MyDateImp birthday) {this.name = name;this.sal = sal;this.birthday = birthday;}
}

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