Java常用工具类—集合排序

//数组的排序
int[] arr= {2,3,4,5,2,1};
Arrays.sort(arr);

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

public class IntSort {

	public static void main(String[] args) {
		//对存储在List中的整形数据进行排序
		List<Integer> list = new ArrayList<Integer>();
		list.add(5);
		list.add(9);
		list.add(3);
		list.add(1);
		System.out.println("排序前：");
		for (int n: list) {
			System.out.print(n + " ");
		}
		System.out.println();
		//对List中的数据进行排序
		Collections.sort(list);
		System.out.println("排序后：");
		for (int n: list) {
			System.out.print(n + " ");
		}
	}
	
}

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

public class StringSort {

	public static void main(String[] args) {
		//对存放在List中的字符串进行排序。
		List<String> list = new ArrayList<String>();
		list.add("orange");
		list.add("blue");
		list.add("yellow");
		list.add("gray");
		System.out.println("排序前: ");
		for (String str: list) {
			System.out.print(str + " ");
		}
		System.out.println();
		//对List中的数据进行排序
		Collections.sort(list);
		System.out.println("排序后: ");
		for (String str: list) {
			System.out.print(str + " ");
		}
		//排序后其实是按字母顺序
	}

}

int n = name1.conpareTo(name2);

import java.util.Comparator;
//按名字进行升序排序的比较器
public class NameComparator implements Comparator<Cat> {

	@Override
	public int compare(Cat o1, Cat o2) {
		//按名字升序排序
		String name1 = o1.getName();
		String name2 = o2.getName();
		int n = name1.compareTo(name2);
		return n;
	}
	
}

Collections.sort(catList, new NameComparator());

import java.util.Comparator;
//按年龄进行降序排序的比较器
public class AgeComparator implements Comparator<Cat> {

	@Override
	public int compare(Cat o1, Cat o2) {
		int age1 = o1.getMonth();
		int age2 = o2.getMonth();
		return age2 - age1;
	}

}

Collections.sort(catList, new AgeComparator());

public class Goods implements Comparable<Goods> { //实现Comparable接口，利用泛型限定比较的类型
	private String id; //商品编号
	private String name; //商品名称
	private double price; //商品价格
	//构造方法
	public Goods() {
		
	}
	public Goods(String id, String name, double price) {
		this.setId(id);
		this.setName(name);
		this.setPrice(price);
	}
	
	//getter和setter方法
	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 double getPrice() {
		return price;
	}
	public void setPrice(double price) {
		this.price = price;
	}
	
	
	@Override
	public String toString() {
		return "商品编号：" + id + ",商品名称：" + name + ",商品价格：" + price;
	}

	@Override
	public int compareTo(Goods o) {  //重写compareTo方法。
		//取出商品价格
		double price1 = this.getPrice();
		double price2 = o.getPrice();
		int n = new Double(price2 - price1).intValue();  //double类型的差值转为int
		return n;
	}

Collections.sort(goodsList);