学步园

自定义了对象，如何按照自定对象中某一或多个元素对其进行排序呢？以下分别从C++和java对其进行实现。

一：C++

/*
实现对自定义的对象类型进行排序(按照其中的元素)，首先将对象存放在vector中，然后利用algorithm库函数中的sort对其进行排序，需要重写排序函数以函数名
作为函数指针作为sort的第三个参数
*/

#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
using namespace std;


struct students{
	int age;
	string name;
};

void addStudents(vector<students> &vec, int age, string name){
	students stu;
	stu.age = age;
	stu.name = name;
	vec.push_back(stu);
	
}

// 按照年龄进行排序 升序
bool sortByAge(const students &s1, const students &s2){
	return s1.age < s2.age;
}


// 先按照年龄进行排序 年纪一样 按照姓名排序
bool sortByAll(const students &s1, const students &s2){
	if(s1.age < s2.age) return true;
	else if(s1.age > s2.age) return false;
	else return s1.name < s2.name;
}
int main(){
	vector<students> vec;
	addStudents(vec, 20, "zhangming");
	addStudents(vec, 20, "xiaoming");
	addStudents(vec, 20, "xiaoming2");
	addStudents(vec, 23, "xiaohong");
	addStudents(vec, 22, "xiaofei");
	addStudents(vec, 27, "xiaogang");
	cout << "排序前:" << endl;
	for(vector<students>::iterator iter = vec.begin(); iter != vec.end(); ++iter){
		cout << (*iter).age << " " << (*iter).name << endl;
	}
	sort(vec.begin(), vec.end(), sortByAll);
	cout << "排序后:" << endl;
	for(vector<students>::iterator iter = vec.begin(); iter != vec.end(); ++iter){
		cout << (*iter).age << " " << (*iter).name << endl;
	}
}

二：Java

主函数sortClass.java：

package com.test.sort;

import java.util.ArrayList;
import java.util.Arrays;

import com.zack.bean.Students;

public class sortClass {
	
	
	/*
	 * ArrayList 中存储了自定义的对象类型， 然后通过toArray()转换为Object类型，再使用java.util.Arrays.sort进行排序
	 * 注意的是排序要重新实现comparator接口进行，作为sort的第二个参数即myComparator对象
	 */

	static ArrayList<Students> arrayList = new ArrayList<Students>();
	public static void addStudents(int age, String username){
		
		Students s = new Students(age, username);
		arrayList.add(s);
	}
	
	@SuppressWarnings("unchecked")
	public static void main(String[] args) {
		addStudents(20, "xiaoming");
		addStudents(20, "zhangming");
		addStudents(20, "xiaoming2");
		addStudents(25, "xiaohong");
		addStudents(23, "xiaogang");
		addStudents(21, "xiaojie");
		System.out.println("排序前:");
		for(int i = 0; i < arrayList.size(); i++)
		{
			System.out.println(arrayList.get(i).getAge() + " ::" + arrayList.get(i).getUsername());
		}
		
		System.out.println("降排序后:");
		Object[] obj = arrayList.toArray();
		Arrays.sort(obj, new myComparator());
		
		for(int i = 0; i < obj.length; i++)
		{
			System.out.println(obj[i]);
		}
	}

}

myComparator.java:

package com.test.sort;

import java.util.Comparator;

import com.zack.bean.Students;

public class myComparator implements Comparator{

	@Override
	public int compare(Object o1, Object o2) {
		// TODO Auto-generated method stub
	
		Students s1 = (Students) o1;
		Students s2 = (Students) o2;
		if(s1.getAge() < s2.getAge())
			return 1;
		else if(s1.getAge() > s2.getAge())
			return -1;
		else return s1.getUsername().compareTo(s2.getUsername());
	}

}

Students.java:

package com.zack.bean;

public class Students {
	private int age;
	private String username;
	
	public Students(int age, String username){
		this.age = age;
		this.username = username;
	}
	
	public int getAge(){
		return this.age;
	}
	public String getUsername(){
		return this.username;
	}
	public String toString(){
		return this.age + "::" + this.username;
	}
}