同java一样：
在为对象数组进行排序时，比较器的作用非常明显，首先来讲解Comparable接口。
让需要进行排序的对象实现Comparable接口，重写其中的compareTo(T o)方法
The implementation of this method should return the following values:
- 0 if this instance and objectToCompareTo are equal
- > 0 if this instance is greater than objectToCompareTo
- < 0 if this instance is less than objectToCompareTo
看例子，这是Comparable接口的示例实现。
global class Employee implements Comparable {
public Long id;
public String name;
public String phone;
// Constructor
public Employee(Long i, String n, String p) {
id = i;
name = n;
phone = p;
}
// Implement the compareTo() method
global Integer compareTo(Object compareTo) {
Employee compareToEmp = (Employee)compareTo;
if (id == compareToEmp.id) return 0;
if (id > compareToEmp.id) return 1;
return -1;
}
}
测试代码：
List<Employee> empList = new List<Employee>(); empList.add(new Employee(101,‘Joe Smith‘, ‘4155551212‘)); empList.add(new Employee(101,‘J. Smith‘, ‘4155551212‘)); empList.add(new Employee(25,‘Caragh Smith‘, ‘4155551000‘)); empList.add(new Employee(105,‘Mario Ruiz‘, ‘4155551099‘)); // Sort using the custom compareTo() method empList.sort(); // Write list contents to the debug log System.debug(empList); // Verify list sort order. System.assertEquals(‘Caragh Smith‘, empList[0].Name); System.assertEquals(‘Joe Smith‘, empList[1].Name); System.assertEquals(‘J. Smith‘, empList[2].Name); System.assertEquals(‘Mario Ruiz‘, empList[3].Name);
原文：http://www.cnblogs.com/bandariFang/p/7094263.html