1.创建比较规则的类，让此类实现Compare接口

2.重写compare（Object o1 ，Object o2）；

3.在方法内制定比较规则

4.创建比较规则对象

5.该对象调用 比较方法 根据放回值 确定哪一个对象大

>0 :前一个对象 >后一个对象

<0 :前一个对象 <后一个对象

==0 :前一个对象 ==后一个对象

按照id比

第一步：创建比较规则的类，让此类实现Compare接口

第二步：重写compare（Object o1 ，Object o2）；

第三步：在方法内制定比较规则

import java.util.Comparator;

public class sortById implements Comparator {
    @Override
    public int compare(Object o1, Object o2) {
        Employee e1 = (Employee)o1;
        Employee e2 = (Employee)o2;
        return e1.id - e2.id;
    }
}

 第四步：创建比较规则对象

第五步：该对象调用 比较方法 根据放回值 确定哪一个对象大

public class Test {
    public static void main(String[] args) {
        Employee e1 = new Employee(1, "张三", 999.9);
        Employee e2 = new Employee(2,"李四",99.6);
        /*创建比较类对象*/
        sortById sortById = new sortById();

        int sort = sortById.compare(e1, e2);
        System.out.println(sort);
    }
}

 JavaBean对象：

public class Employee {
    int id;
    String name;
    double salary;

    public Employee() {
    }

    public Employee(int id, String name, double salary) {
        this.id = id;
        this.name = name;
        this.salary = salary;
    }

    @Override
    public String toString() {
        return "Person{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", salary=" + salary +
                '}';
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }


}

数组工具类和外部比较器结合使用

按照id值进行排序

import java.util.Arrays;

public class Test {
    public static void main(String[] args) {
        Employee e1 = new Employee(1,"张三",9999.9);
        Employee e2 = new Employee(6,"李四",9999.3);
        Employee e3 = new Employee(3,"王五",9999.3);
        Employee e4 = new Employee(4,"赵六",9999.9);
        Employee e5 = new Employee(2,"陈七",9999.8);
        Employee [] es = {e1,e2,e3,e4,e5};
        /*创建比较类对象*/
        sortById sortById = new sortById();
        Arrays.sort(es, sortById);
        for (Employee ele :es){
            System.out.println(ele);
        }
    }
}