Java对象排序

java实现对象比较，可以实现java.lang.Comparable或java.util.Comparator接口

//Product.java

import java.util.Date;

//public class Product implements Comparable {//类内比较
public class Product{

    private String name;
    private Date date;
    private int price;

    public int getPrice() {
        return price;
    }
    public void setPrice(int price) {
        this.price = price;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Date getDate() {
        return date;
    }
    public void setDate(Date date) {
        this.date = date;
    }

//用于类内比较
//  @Override//覆写compareTo(Object o)方法
//  public int compareTo(Product o) {
//      return -this.date.compareTo(o.date);
//  }

}

//ProductComparable.java

import java.util.Date;
import java.util.Comparator;

public class ProductComparable implements Comparator<Product> {

    // 对象的排序方式[升、降]
    public static boolean sortASC = true;

    // 对象的排序属性
    public static boolean sortByName = false;
    public static boolean sortByDate = false;
    public static boolean sortByPrice = false;


    @Override
    public int compare(Product pro1, Product pro2) {

        int result = 0;

        if(sortASC){
            if(sortByName){
                String pro1name = pro1.getName();
                String pro2name = pro2.getName();
                result = pro1name.compareTo(pro2name);
            }else if(sortByDate){
                Date pro1Date = pro1.getDate();
                Date pro2Date = pro2.getDate();

                result = pro1Date.compareTo(pro2Date);

            }else if(sortByPrice){
                Integer pro1Price = pro1.getPrice();
                Integer pro2Price = pro2.getPrice();

                result = pro1Price.compareTo(pro2Price);
            }
        }else{
            if(sortByName){
                String pro1name = pro1.getName();
                String pro2name = pro2.getName();

                result =  -pro1name.compareTo(pro2name);
            }else if(sortByDate){
                Date pro1Date = pro1.getDate();
                Date pro2Date = pro2.getDate();

                result =  -pro1Date.compareTo(pro2Date);

            }else if(sortByPrice){
                Integer pro1Price = pro1.getPrice();
                Integer pro2Price = pro2.getPrice();

                result =  -pro1Price.compareTo(pro2Price);
            }
        }
        return result;
    }

}

//测试代码

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;

public class ProductSort {

    public static void main(String[] args) throws ParseException {
        Product pro1 = new Product();
        pro1.setName("pro1");
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-dd-MM",Locale.CHINA);
        pro1.setDate(sdf.parse("2009-03-23"));
        pro1.setPrice(89);
        Product pro2 = new Product();
        pro2.setName("proc2");
        pro2.setDate(sdf.parse("2009-02-23"));
        pro2.setPrice(45);
        Product pro3 = new Product();
        pro3.setName("proc3");
        pro3.setDate(sdf.parse("2009-01-23"));
        pro3.setPrice(83);
        Product pro4 = new Product();
        pro4.setName("proc4");
        pro4.setDate(sdf.parse("2009-01-23"));
        pro4.setPrice(800);


        List<Product> productList = new ArrayList<Product>();
        productList.add(pro1);
        productList.add(pro3);
        productList.add(pro2);
        productList.add(pro4);

        System.out.println("排序前————————————————————");
        for(Product p: productList){
            System.out.println(p.getName()+"----"+p.getPrice()+"----"+p.getDate());
        }
        ProductComparable sort = new ProductComparable();

        ProductComparable.sortASC = false;//降序
        ProductComparable.sortByPrice=true;  //设置排序属性生效
        Collections.sort(productList,sort);

        System.out.println("排序后————————————————————");

        for(Iterator<Product>  iter = productList.iterator(); iter.hasNext();){
            Product p = (Product)iter.next();
            System.out.println(p.getName()+"----"+p.getPrice()+"---"+p.getDate());
        }
    }
}

 推荐使用Comparator实现排序

因为 你用一个第三方的类，但他没实现Comparable接口，而你又不能改他代码；另外，类一旦写好后是不允许修改的，但可以扩展，所以只能用Comparator接口

java实现对象比较，可以实现java.lang.Comparable或java.util.Comparator接口

//Product.java

import java.util.Date;

//public class Product implements Comparable {//类内比较
public class Product{

    private String name;
    private Date date;
    private int price;

    public int getPrice() {
        return price;
    }
    public void setPrice(int price) {
        this.price = price;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Date getDate() {
        return date;
    }
    public void setDate(Date date) {
        this.date = date;
    }

//用于类内比较
//  @Override//覆写compareTo(Object o)方法
//  public int compareTo(Product o) {
//      return -this.date.compareTo(o.date);
//  }

}

//ProductComparable.java

import java.util.Date;
import java.util.Comparator;

public class ProductComparable implements Comparator<Product> {

    // 对象的排序方式[升、降]
    public static boolean sortASC = true;

    // 对象的排序属性
    public static boolean sortByName = false;
    public static boolean sortByDate = false;
    public static boolean sortByPrice = false;


    @Override
    public int compare(Product pro1, Product pro2) {

        int result = 0;

        if(sortASC){
            if(sortByName){
                String pro1name = pro1.getName();
                String pro2name = pro2.getName();
                result = pro1name.compareTo(pro2name);
            }else if(sortByDate){
                Date pro1Date = pro1.getDate();
                Date pro2Date = pro2.getDate();

                result = pro1Date.compareTo(pro2Date);

            }else if(sortByPrice){
                Integer pro1Price = pro1.getPrice();
                Integer pro2Price = pro2.getPrice();

                result = pro1Price.compareTo(pro2Price);
            }
        }else{
            if(sortByName){
                String pro1name = pro1.getName();
                String pro2name = pro2.getName();

                result =  -pro1name.compareTo(pro2name);
            }else if(sortByDate){
                Date pro1Date = pro1.getDate();
                Date pro2Date = pro2.getDate();

                result =  -pro1Date.compareTo(pro2Date);

            }else if(sortByPrice){
                Integer pro1Price = pro1.getPrice();
                Integer pro2Price = pro2.getPrice();

                result =  -pro1Price.compareTo(pro2Price);
            }
        }
        return result;
    }

}

//测试代码

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Locale;

public class ProductSort {

    public static void main(String[] args) throws ParseException {
        Product pro1 = new Product();
        pro1.setName("pro1");
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-dd-MM",Locale.CHINA);
        pro1.setDate(sdf.parse("2009-03-23"));
        pro1.setPrice(89);
        Product pro2 = new Product();
        pro2.setName("proc2");
        pro2.setDate(sdf.parse("2009-02-23"));
        pro2.setPrice(45);
        Product pro3 = new Product();
        pro3.setName("proc3");
        pro3.setDate(sdf.parse("2009-01-23"));
        pro3.setPrice(83);
        Product pro4 = new Product();
        pro4.setName("proc4");
        pro4.setDate(sdf.parse("2009-01-23"));
        pro4.setPrice(800);


        List<Product> productList = new ArrayList<Product>();
        productList.add(pro1);
        productList.add(pro3);
        productList.add(pro2);
        productList.add(pro4);

        System.out.println("排序前————————————————————");
        for(Product p: productList){
            System.out.println(p.getName()+"----"+p.getPrice()+"----"+p.getDate());
        }
        ProductComparable sort = new ProductComparable();

        ProductComparable.sortASC = false;//降序
        ProductComparable.sortByPrice=true;  //设置排序属性生效
        Collections.sort(productList,sort);

        System.out.println("排序后————————————————————");

        for(Iterator<Product>  iter = productList.iterator(); iter.hasNext();){
            Product p = (Product)iter.next();
            System.out.println(p.getName()+"----"+p.getPrice()+"---"+p.getDate());
        }
    }
}

 推荐使用Comparator实现排序

因为 你用一个第三方的类，但他没实现Comparable接口，而你又不能改他代码；另外，类一旦写好后是不允许修改的，但可以扩展，所以只能用Comparator接口