用Java集合中的Collections.sort方法对list排序的两种方法
fmms
13年前
<div class="BlogContent TextContent"> <div class="cnt"> <p><strong>用Collections.sort方法对list排序有两种方法<br /> 第一种是list中的对象实现Comparable接口，如下：</strong><br /> </p> <pre class="brush:java; toolbar: true; auto-links: false;">/** * 根据order对User排序 */ public class User implements Comparable <user> { private String name; private Integer order; public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getOrder() { return order; } public void setOrder(Integer order) { this.order = order; } public int compareTo(User arg0) { return this.getOrder().compareTo(arg0.getOrder()); } } </user></pre> <br /> 测试一下： <br /> <pre class="brush:java; toolbar: true; auto-links: false;">public class Test{ public static void main(String[] args) { User user1 = new User(); user1.setName("a"); user1.setOrder(1); User user2 = new User(); user2.setName("b"); user2.setOrder(2); List <user> list = new ArrayList <user> (); //此处add user2再add user1 list.add(user2); list.add(user1); Collections.sort(list); for(User u : list){ System.out.println(u.getName()); } } } </user> </user></pre> <br /> 输出结果如下 <br /> <strong>a<br /> b</strong> <br /> <strong>第二种方法是根据Collections.sort重载方法来实现，例如：</strong> <br /> <pre class="brush:java; toolbar: true; auto-links: false;">/** * 根据order对User排序 */ public class User { //此处无需实现Comparable接口 private String name; private Integer order; public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getOrder() { return order; } public void setOrder(Integer order) { this.order = order; } }</pre> <br /> 主类中这样写即可： <br /> <pre class="brush:java; toolbar: true; auto-links: false;">public class Test{ public static void main(String[] args) { User user1 = new User(); user1.setName("a"); user1.setOrder(1); User user2 = new User(); user2.setName("b"); user2.setOrder(2); List <user> list = new ArrayList <user> (); list.add(user2); list.add(user1); Collections.sort(list,new Comparator <user> (){ public int compare(User arg0, User arg1) { return arg0.getOrder().compareTo(arg1.getOrder()); } }); for(User u : list){ System.out.println(u.getName()); } } } </user> </user> </user></pre> <br /> 输出结果如下 <br /> <strong>a<br /> b</strong> <br /> 前者代码结构简单，但是只能根据固定的属性排序，后者灵活，可以临时指定排序项，但是代码不够简洁 <br /> <br /> 多字段的场合： <br /> <strong><pre class="brush:java; toolbar: true; auto-links: false;">Collections.sort(list,new Comparator <user> (){ public int compare(User arg0, User arg1) { // 第一次比较专业 int i = arg0.getOrder().compareTo(arg1.getOrder()); // 如果专业相同则进行第二次比较 if(i==0){ // 第二次比较 int j=arg0.getXXX().compareTo(arg1.getXXX()); // 如果学制相同则返回按年龄排序 if(j==0){ return arg0.getCCC().compareTo(arg1.getCCC()); } return j; } return i; } }); </user></pre></strong> <p></p> </div> </div>