collection-sort

集合元素排序

1.包装类型数据排序

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Random;

public class CollectionSortTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		List<Integer> listInteger = new ArrayList<Integer>();
		Random random = new Random(1);
		for(Integer index = 0 ; index <= 10 ; index ++){
			listInteger.add(random.nextInt(100));
		}
                // 默认按照升序排列
		Collections.sort(listInteger);
		System.out.println(listInteger);
                // 倒叙：添加比较器；原则：返回值为-1交换元素；1不交换
                // 倒叙：在返回值前添加-1，就会使返回值的正负属性颠倒
		Comparator<Integer> integerDesc = new Comparator<Integer>() {

			@Override
			public int compare(Integer o1, Integer o2) {
				return  -(o1 < o2 ? -1 : o1 > 02 ? 1 : 0);
			}
		};
		Collections.sort(listInteger,integerDesc);
		System.out.println(listInteger);
	}

}

2.对象比较

固定排序顺序

按价格倒叙，按销量升序

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class CollectionObjectSortTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		List<Product> productList = new ArrayList<Product>();
		
		Product product1 = new Product("商品1", 20.00, 100);
		Product product2 = new Product("商品2", 20.00, 200);
		Product product3 = new Product("商品3", 30.00, 100);
		Product product4 = new Product("商品4", 50.00, 100);
	
		productList.add(product1);
		productList.add(product2);
		productList.add(product3);
		productList.add(product4);
		Collections.sort(productList);
		System.out.println(productList);
	}

}
class Product implements Comparable<Product>{
	private String name ;
	private Double price ; // 价格
	private Integer amount ; // 销售总量
	public Product() {
		super();
	}
	public Product(String name, Double price, Integer amount) {
		super();
		this.name = name;
		this.price = price;
		this.amount = amount;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Double getPrice() {
		return price;
	}
	public void setPrice(Double price) {
		this.price = price;
	}
	public Integer getAmount() {
		return amount;
	}
	public void setAmount(Integer amount) {
		this.amount = amount;
	}
	@Override
	public String toString() {
		return "Product [name=" + name + ", price=" + price + ", amount="
				+ amount + "]";
	}
	@Override
	public int compareTo(Product o) {
		if(!this.price.equals(o.price )){
			return -(this.price < o.price ?-1:this.price > o.price ? 1 : 0 );
		}else{
			return this.amount < o.amount ? -1 : this.amount > o.amount ? 1 : 0;
		}
	}
	
}

3.动态排序

通过 Compartor<Product> byPriceAndAmount = new Compator<Product>(){}
重复上面的比较条件即可

4.比较

固定排序，不可改变排序顺序；但如果需求是动态排序，则使用后者