比较

比较器：
 Comparable: 内部比较器，实现相对简单 缺点是要修改源代码
 Comparator: 外部比较器，优点是不需要修改源代码 

Comparable:  内部比较器

package Content;

import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Collections;
import java.util.TreeSet;



//Comparable:  内部比较器
public class CollectionSortDemo_Comparable {

    static class Student implements Comparable<Student>{
        String name;
        int mark;

        public Student (String name,int mark) {
            this.name = name;
            this.mark = mark;
        }

        public int compareTo(Student oStudent) {
            //this>o 从小到大
            if(this.mark>oStudent.mark) {
                return 1;
            }else if(this.mark<oStudent.mark) {
                return -1;
            }else {
                return this.name.compareTo(oStudent.name);
            }
        }

    }

    public static void main(String[] args) {

        ArrayList<String> arrayList = new ArrayList<String>();
        arrayList.add("Jhon");
        arrayList.add("Tom");
        arrayList.add("Jerry");
        arrayList.add("Anna");
        System.out.println(arrayList);

        //排序
        Collections.sort(arrayList);
        System.out.println(arrayList);
        System.out.println();

        ArrayList<Integer> arrayList2 = new ArrayList<Integer>();
        arrayList2.add(6);
        arrayList2.add(5);
        arrayList2.add(1);
        arrayList2.add(3);
        arrayList2.add(2);

        System.out.println(arrayList2);
        Collections.sort(arrayList2);
        System.out.println(arrayList2);
        System.out.println();

        ArrayList<Student> studentlist = new ArrayList<>();
        studentlist.add(new Student("Jhon", 80));
        studentlist.add(new Student("Tom", 60));
        studentlist.add(new Student("Jerry", 90));
        studentlist.add(new Student("Amy", 90));
        studentlist.add(new Student("Anna", 100));

        for(Student e:studentlist) {
            System.out.println(e.name+"  "+e.mark);
        }
        System.out.println();
        System.out.println("Sort:");
        Collections.sort(studentlist);
        for(Student e:studentlist) {
            System.out.println(e.name+"  "+e.mark);
        }

        System.out.println();

        System.out.println("TreeSet:");
        TreeSet<Student> studentSet = new TreeSet<>();
        studentSet.add(new Student("Jhon", 80));
        studentSet.add(new Student("Tom", 60));
        studentSet.add(new Student("Jerry", 90));
        studentSet.add(new Student("Amy", 90));
        studentSet.add(new Student("Anna", 100));

        for(Student e:studentSet) {
            System.out.println(e.name+" "+e.mark);
        }


    }

}

View Code

Comparator:  外部比较器

package Content;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.TreeSet;

//Comparator:  外部比较器
public class CollectionSortDemo_Comparator {

    static class Employee {
        String name;
        double salary;
        public Employee(String name,double salary) {
            this.name = name;
            this.salary = salary;
        }
    }
    static class EmployeeComparator implements Comparator<Employee>{
        public int compare(Employee oEmployee, Employee oEmployee2) {
            if (oEmployee.salary> oEmployee2.salary) {
                return 1;
            } else if (oEmployee.salary < oEmployee2.salary) {
                return -1;
            } else {
                return oEmployee.name.compareTo(oEmployee2.name);
            }
        }
    }
    public static void main(String[] args) {
        TreeSet<Employee> employeesSet = new TreeSet<>(new EmployeeComparator());
        employeesSet.add(new Employee("Jhon", 8000));
        employeesSet.add(new Employee("Tom", 6000));
        employeesSet.add(new Employee("Jerry", 9000));
        employeesSet.add(new Employee("Anna", 10000));

        for(Employee e:employeesSet) {
            System.out.println(e.name+" "+e.salary);
        }

//        Collections.sort(employeeslist,new EmployeeComparator());

    }

}

View Code