算法底層實際是 將集合轉換成array，再執行arrays.sort，arrays.sort利用歸並排序，優化的快排，timSort等方式。

2、對string類型數據排序

public static void collectionSort() {
		List<String> unSorted = new ArrayList<String>();
		unSorted.add("10");
		unSorted.add("99");
		unSorted.add("21");
		Collections.sort(unSorted);
		for(String a:unSorted) {
			System.out.print(a +"  ");

		}
	}

輸出：10 21 99

3、對javabean類型數據排序

（1）方式一

import java.io.Serializable;

public class unSortedBean implements Serializable{

	private static final long serialVersionUID = 1L;
	
	private String name;
	private String age;
	private int order;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getAge() {
		return age;
	}
	public void setAge(String age) {
		this.age = age;
	}
	public int getOrder() {
		return order;
	}
	public void setOrder(int order) {
		this.order = order;
	}

}

以下為排序代碼，編譯期就報錯：

public static void javaBeanSort() {
		List<unSortedBean> unSorted = new ArrayList<unSortedBean>();
		unSortedBean a1 = new unSortedBean();
		a1.setName("張三");
		a1.setAge("24");
		a1.setOrder(9);
		unSorted.add(a1);
		unSortedBean a2 = new unSortedBean();
		a2.setName("李四");
		a2.setAge("22");
		a2.setOrder(5);
		unSorted.add(a2);
		unSortedBean a3 = new unSortedBean();
		a3.setName("王五");
		a3.setAge("36");
		a3.setOrder(10);
		unSorted.add(a3);
		Collections.sort(unSorted);
	}

原因：string實現了comparable接口，而自定義的javabean未實現，可以用這種方式排序

Collections.sort(unSorted,new Comparator<unSortedBean>() {

			@Override
			public int compare(unSortedBean arg0, unSortedBean arg1) {
				// 升敘
				return arg0.getOrder()-arg1.getOrder();
			}
		});
		for(unSortedBean bean:unSorted) {
			System.out.print(JSONObject.fromObject(bean));
		}

輸出：{"order":5,"name":"李四","age":"22"}{"order":9,"name":"張三","age":"24"}{"order":10,"name":"王五","age":"36"}

（2）方式二

也可以用collections.sort();方式，只需要javabean實現comparable接口

import java.io.Serializable;

public class unSortedBean implements Serializable, Comparable<unSortedBean>{

	private static final long serialVersionUID = 1L;
	
	private String name;
	private String age;
	private int order;
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getAge() {
		return age;
	}
	public void setAge(String age) {
		this.age = age;
	}
	
	public int getOrder() {
		return order;
	}
	public void setOrder(int order) {
		this.order = order;
	}
	@Override
	public int compareTo(unSortedBean arg0) {
		// TODO 升敘
		return this.order-arg0.getOrder();
	}
	

}

輸出：{"order":5,"name":"李四","age":"22"}{"order":9,"name":"張三","age":"24"}{"order":10,"name":"王五","age":"36"}

註意：如果order是string型數字，需要轉換成數字型再比較，否則比較結果可能不是預期效果。

比如把本文中的order全部換成string型，輸出結果為

{"order":10,"name":"王五","age":"36"}{"order":5,"name":"李四","age":"22"}{"order":9,"name":"張三","age":"24"}

collections.sort對javabean的list進行排序