一个排序框架

Tools中是排序的实现过程，用了一个泛型参数T

import java.util.ArrayList;

public class Tools<T>
{
	public  void sortlist(ArrayList<T> list, Bijiaoqi<T> bijiaoqi)
	{
		for (int i=0; i<list.size()-1; i++)
		{
			for (int j=0; j<list.size()-i-1; j++)
			{
				if (bijiaoqi.bijiao(list.get(j), list.get(j+1)))
				{
					T tmp = list.get(j);
					list.set(j, list.get(j+1));
					list.set(j+1, tmp);
				}
			}
		}
	}
}

Bijiaoqi是一个接口

public interface Bijiaoqi<T>
{
	public boolean bijiao(T t1,T t2);
}

Age是Bijiaoqi接口的一个实现，如果需要比别的属性，就写一个新的实现就行

public class Age implements Bijiaoqi<User>
{

	@Override
	public boolean bijiao(User u1, User u2)
	{
		if (u1.getAge() < u2.getAge())// TODO Auto-generated method stub
		{
			return true;
		}
		return false;
	}

}

一个User类

public class User
{
	private String id;
	private String name;
	private int age;
	private float salary;
	
	public User(String id, String name, int age, float salary)
	{
		this.id = id;
		this.name = name;
		this.age = age;
		this.salary = salary;
	}

	public String getId()
	{
		return id;
	}

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

	public String getName()
	{
		return name;
	}

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

	public int getAge()
	{
		return age;
	}

	public void setAge(int age)
	{
		this.age = age;
	}

	public float getSalary()
	{
		return salary;
	}

	public void setSalary(float salary)
	{
		this.salary = salary;
	}
	
	public String toString()
	{
		return this.name+";"+this.age+";"+this.salary;
	}
}

main入口

public class test
{
	public static void main(String[] args)
	{
		ArrayList<User> list1 = new ArrayList<User>();
		User u1 = new User("1", "a", 10, 100);
		User u2 = new User("2", "b", 5, 200);
		User u3 = new User("3", "c", 17, 300);
		User u4 = new User("4", "d", 6, 5000);
		list1.add(u1);
		list1.add(u2);
		list1.add(u3);
		list1.add(u4);
		
		Tools tools = new Tools();
		Bijiaoqi age = new Age();
		tools.sortlist(list1, new Age());

		for (User u:list1)
		{
			System.out.println(u);
		}
	}
}

这里也可以使用匿名内部类来传递比较器对象，就不用重新写个类去实现接口，直接在调用的时候写实现。

public class test
{
	public static void main(String[] args)
	{
		ArrayList<User> list1 = new ArrayList<User>();
		User u1 = new User("1", "a", 10, 100);
		User u2 = new User("2", "b", 5, 200);
		User u3 = new User("3", "c", 17, 300);
		User u4 = new User("4", "d", 6, 5000);
		list1.add(u1);
		list1.add(u2);
		list1.add(u3);
		list1.add(u4);
		
		Tools tools = new Tools();
		Bijiaoqi age = new Age();
		tools.sortlist(list1, new Bijiaoqi<User>() 
		{
			@Override
			public boolean bijiao(User u1, User u2)
			{
				if (u1.getAge()<u2.getAge())
				{
					return true;
				}
				return false;
			}
			
		});

		for (User u:list1)
		{
			System.out.println(u);
		}
	}
}

============================================================
使用Collections自带的排序方法，一种方法是参数中new一个匿名内部类Comparator

public class test
{
	public static void main(String[] args)
	{
		ArrayList<User> list1 = new ArrayList<User>();
		User u1 = new User("1", "a", 10, 100);
		User u2 = new User("2", "b", 5, 200);
		User u3 = new User("3", "c", 17, 300);
		User u4 = new User("4", "d", 6, 5000);
		list1.add(u1);
		list1.add(u2);
		list1.add(u3);
		list1.add(u4);
		
		Collections.sort(list1, new Comparator<User>() 
		{
			@Override
			public int compare(User u1, User u2)
			{
				if (u1.getAge()<u2.getAge())
				{
					return 1;
				}
				return -1;
			}
		});
		for (User u:list1)
		{
			System.out.println(u);
		}
	}
}

或者让list中的对象自身能够比较大小(重构Comparable接口的compareTo方法)

public class User implements Comparable<User>
{
	public User(String id, String name, int age, float salary)
	{
		public int compareTo(User other)
		{
			if (this.getAge()>other.getAge())
			{
				return 1;
			}
			return -1;
		}
}

public class test
{
	public static void main(String[] args)
	{
		ArrayList<User> list1 = new ArrayList<User>();
		User u1 = new User("1", "a", 10, 100);
		User u2 = new User("2", "b", 5, 200);
		User u3 = new User("3", "c", 17, 300);
		User u4 = new User("4", "d", 6, 5000);
		list1.add(u1);
		list1.add(u2);
		list1.add(u3);
		list1.add(u4);
		
		Collections.sort(list1);
		for (User u:list1)
		{
			System.out.println(u);
		}
	}
}