Shulou(Shulou.com)06/03 Report--

1、collection.sort排序

算法底层实际是 将集合转换成array，再执行arrays.sort，arrays.sort利用归并排序，优化的快排，timSort等方式。

2、对string类型数据排序

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

输出：10 21 99

3、对javabean类型数据排序

（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; }}

以下为排序代码，编译期就报错：

public static void javaBeanSort() { List unSorted = new ArrayList(); unSortedBean a1 = new unSortedBean(); a1.setName("张三"); 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实现了comparable接口，而自定义的javabean未实现，可以用这种方式排序

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

输出：{"order":5,"name":"李四","age":"22"}{"order":9,"name":"张三","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实现comparable接口

import java.io.Serializable;public class unSortedBean implements Serializable, Comparable{ 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 升叙 return this.order-arg0.getOrder(); } }

输出：{"order":5,"name":"李四","age":"22"}{"order":9,"name":"张三","age":"24"}{"order":10,"name":"王五","age":"36"}

注意：如果order是string型数字，需要转换成数字型再比较，否则比较结果可能不是预期效果。

比如把本文中的order全部换成string型，输出结果为

{"order":10,"name":"王五","age":"36"}{"order":5,"name":"李四","age":"22"}{"order":9,"name":"张三","age":"24"}

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